Don't use SkipLocalsInit

.editorconfig

@@ -1,543 +0,0 @@
-# Version: 2.0.1 (Using https://semver.org/)
-# Updated: 2020-12-11
-# See https://github.com/RehanSaeed/EditorConfig/releases for release notes.
-# See https://github.com/RehanSaeed/EditorConfig for updates to this file.
-# See http://EditorConfig.org for more information about .editorconfig files.
-
-##########################################
-# Common Settings
-##########################################
-
-# This file is the top-most EditorConfig file
-root = true
-
-# All Files
-[*]
-charset = utf-8
-indent_style = space
-indent_size = 4
-insert_final_newline = true
-trim_trailing_whitespace = true
-
-##########################################
-# File Extension Settings
-##########################################
-
-# Visual Studio Solution Files
-[*.sln]
-indent_style = tab
-
-# Visual Studio XML Project Files
-[*.{csproj,vbproj,vcxproj.filters,proj,projitems,shproj}]
-indent_size = 2
-
-# XML Configuration Files
-[*.{xml,config,props,targets,nuspec,resx,ruleset,vsixmanifest,vsct}]
-indent_size = 2
-
-# JSON Files
-[*.{json,json5,webmanifest}]
-indent_size = 2
-
-# YAML Files
-[*.{yml,yaml}]
-indent_size = 2
-
-# Markdown Files
-[*.md]
-trim_trailing_whitespace = false
-
-# Web Files
-[*.{htm,html,js,jsm,ts,tsx,css,sass,scss,less,svg,vue}]
-indent_size = 2
-
-# Batch Files
-[*.{cmd,bat}]
-end_of_line = crlf
-
-# Bash Files
-[*.sh]
-end_of_line = lf
-
-# Makefiles
-[Makefile]
-indent_style = tab
-
-##########################################
-# Default .NET Code Style Severities
-# https://docs.microsoft.com/dotnet/fundamentals/code-analysis/configuration-options#scope
-##########################################
-
-[*.{cs,csx,cake,vb,vbx}]
-# Default Severity for all .NET Code Style rules below
-dotnet_analyzer_diagnostic.severity = warning
-
-##########################################
-# File Header (Uncomment to support file headers)
-# https://docs.microsoft.com/visualstudio/ide/reference/add-file-header
-##########################################
-
-# [*.{cs,csx,cake,vb,vbx}]
-# file_header_template = <copyright file="{fileName}" company="PROJECT-AUTHOR">\n© PROJECT-AUTHOR\n</copyright>
-
-# SA1636: File header copyright text should match
-# Justification: .editorconfig supports file headers. If this is changed to a value other than "none", a stylecop.json file will need to added to the project.
-# dotnet_diagnostic.SA1636.severity = none
-
-##########################################
-# .NET Language Conventions
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions
-##########################################
-
-# .NET Code Style Settings
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#net-code-style-settings
-[*.{cs,csx,cake,vb,vbx}]
-# "this." and "Me." qualifiers
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#this-and-me
-#dotnet_style_qualification_for_field = true:warning
-#dotnet_style_qualification_for_property = true:warning
-#dotnet_style_qualification_for_method = true:warning
-#dotnet_style_qualification_for_event = true:warning
-# Language keywords instead of framework type names for type references
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#language-keywords
-dotnet_style_predefined_type_for_locals_parameters_members = true:warning
-dotnet_style_predefined_type_for_member_access = true:warning
-# Modifier preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#normalize-modifiers
-dotnet_style_require_accessibility_modifiers = always:warning
-csharp_preferred_modifier_order = public,private,protected,internal,static,extern,new,virtual,abstract,sealed,override,readonly,unsafe,volatile,async:warning
-visual_basic_preferred_modifier_order = Partial,Default,Private,Protected,Public,Friend,NotOverridable,Overridable,MustOverride,Overloads,Overrides,MustInherit,NotInheritable,Static,Shared,Shadows,ReadOnly,WriteOnly,Dim,Const,WithEvents,Widening,Narrowing,Custom,Async:warning
-dotnet_style_readonly_field = true:warning
-# Parentheses preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#parentheses-preferences
-dotnet_style_parentheses_in_arithmetic_binary_operators = always_for_clarity:warning
-dotnet_style_parentheses_in_relational_binary_operators = always_for_clarity:warning
-dotnet_style_parentheses_in_other_binary_operators = always_for_clarity:warning
-dotnet_style_parentheses_in_other_operators = always_for_clarity:suggestion
-# Expression-level preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#expression-level-preferences
-dotnet_style_object_initializer = true:warning
-dotnet_style_collection_initializer = true:warning
-dotnet_style_explicit_tuple_names = true:warning
-dotnet_style_prefer_inferred_tuple_names = true:warning
-dotnet_style_prefer_inferred_anonymous_type_member_names = true:warning
-dotnet_style_prefer_auto_properties = true:warning
-dotnet_style_prefer_is_null_check_over_reference_equality_method = true:warning
-dotnet_style_prefer_conditional_expression_over_assignment = false:suggestion
-dotnet_diagnostic.IDE0045.severity = suggestion
-dotnet_style_prefer_conditional_expression_over_return = false:suggestion
-dotnet_diagnostic.IDE0046.severity = suggestion
-dotnet_style_prefer_compound_assignment = true:warning
-# Null-checking preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#null-checking-preferences
-dotnet_style_coalesce_expression = true:warning
-dotnet_style_null_propagation = true:warning
-# Parameter preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#parameter-preferences
-dotnet_code_quality_unused_parameters = all:warning
-# More style options (Undocumented)
-# https://github.com/MicrosoftDocs/visualstudio-docs/issues/3641
-dotnet_style_operator_placement_when_wrapping = end_of_line
-# https://github.com/dotnet/roslyn/pull/40070
-dotnet_style_prefer_simplified_interpolation = true:warning
-
-# C# Code Style Settings
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#c-code-style-settings
-[*.{cs,csx,cake}]
-# Implicit and explicit types
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#implicit-and-explicit-types
-csharp_style_var_for_built_in_types = true:warning
-csharp_style_var_when_type_is_apparent = true:warning
-csharp_style_var_elsewhere = true:warning
-# Expression-bodied members
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#expression-bodied-members
-csharp_style_expression_bodied_methods = true:warning
-csharp_style_expression_bodied_constructors = true:warning
-csharp_style_expression_bodied_operators = true:warning
-csharp_style_expression_bodied_properties = true:warning
-csharp_style_expression_bodied_indexers = true:warning
-csharp_style_expression_bodied_accessors = true:warning
-csharp_style_expression_bodied_lambdas = true:warning
-csharp_style_expression_bodied_local_functions = true:warning
-# Pattern matching
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#pattern-matching
-csharp_style_pattern_matching_over_is_with_cast_check = true:warning
-csharp_style_pattern_matching_over_as_with_null_check = true:warning
-# Inlined variable declarations
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#inlined-variable-declarations
-csharp_style_inlined_variable_declaration = true:warning
-# Expression-level preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#expression-level-preferences
-csharp_prefer_simple_default_expression = true:warning
-# "Null" checking preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#c-null-checking-preferences
-csharp_style_throw_expression = true:warning
-csharp_style_conditional_delegate_call = true:warning
-# Code block preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#code-block-preferences
-csharp_prefer_braces = true:warning
-# Unused value preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#unused-value-preferences
-csharp_style_unused_value_expression_statement_preference = discard_variable:suggestion
-dotnet_diagnostic.IDE0058.severity = suggestion
-csharp_style_unused_value_assignment_preference = discard_variable:suggestion
-dotnet_diagnostic.IDE0059.severity = suggestion
-# Index and range preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#index-and-range-preferences
-csharp_style_prefer_index_operator = true:warning
-csharp_style_prefer_range_operator = true:warning
-# Miscellaneous preferences
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-language-conventions#miscellaneous-preferences
-csharp_style_deconstructed_variable_declaration = true:warning
-csharp_style_pattern_local_over_anonymous_function = true:warning
-csharp_using_directive_placement = outside_namespace:warning
-csharp_prefer_static_local_function = true:warning
-csharp_prefer_simple_using_statement = true:suggestion
-dotnet_diagnostic.IDE0063.severity = suggestion
-
-csharp_style_namespace_declarations = file_scoped
-
-##########################################
-# .NET Formatting Conventions
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-code-style-settings-reference#formatting-conventions
-##########################################
-
-# Organize usings
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-formatting-conventions#organize-using-directives
-dotnet_sort_system_directives_first = true
-# Newline options
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-formatting-conventions#new-line-options
-csharp_new_line_before_open_brace = all
-csharp_new_line_before_else = true
-csharp_new_line_before_catch = true
-csharp_new_line_before_finally = true
-csharp_new_line_before_members_in_object_initializers = true
-csharp_new_line_before_members_in_anonymous_types = true
-csharp_new_line_between_query_expression_clauses = true
-# Indentation options
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-formatting-conventions#indentation-options
-csharp_indent_case_contents = true
-csharp_indent_switch_labels = true
-csharp_indent_labels = no_change
-csharp_indent_block_contents = true
-csharp_indent_braces = false
-csharp_indent_case_contents_when_block = false
-# Spacing options
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-formatting-conventions#spacing-options
-csharp_space_after_cast = false
-csharp_space_after_keywords_in_control_flow_statements = true
-csharp_space_between_parentheses = false
-csharp_space_before_colon_in_inheritance_clause = true
-csharp_space_after_colon_in_inheritance_clause = true
-csharp_space_around_binary_operators = before_and_after
-csharp_space_between_method_declaration_parameter_list_parentheses = false
-csharp_space_between_method_declaration_empty_parameter_list_parentheses = false
-csharp_space_between_method_declaration_name_and_open_parenthesis = false
-csharp_space_between_method_call_parameter_list_parentheses = false
-csharp_space_between_method_call_empty_parameter_list_parentheses = false
-csharp_space_between_method_call_name_and_opening_parenthesis = false
-csharp_space_after_comma = true
-csharp_space_before_comma = false
-csharp_space_after_dot = false
-csharp_space_before_dot = false
-csharp_space_after_semicolon_in_for_statement = true
-csharp_space_before_semicolon_in_for_statement = false
-csharp_space_around_declaration_statements = false
-csharp_space_before_open_square_brackets = false
-csharp_space_between_empty_square_brackets = false
-csharp_space_between_square_brackets = false
-# Wrapping options
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-formatting-conventions#wrap-options
-csharp_preserve_single_line_statements = false
-csharp_preserve_single_line_blocks = true
-
-##########################################
-# .NET Naming Conventions
-# https://docs.microsoft.com/visualstudio/ide/editorconfig-naming-conventions
-##########################################
-
-[*.{cs,csx,cake,vb,vbx}]
-dotnet_diagnostic.CA1000.severity = suggestion
-dotnet_diagnostic.CA1001.severity = error
-dotnet_diagnostic.CA1018.severity = error
-dotnet_diagnostic.CA1051.severity = suggestion
-dotnet_diagnostic.CA1068.severity = error
-dotnet_diagnostic.CA1069.severity = error
-dotnet_diagnostic.CA1304.severity = error
-dotnet_diagnostic.CA1305.severity = suggestion
-dotnet_diagnostic.CA1309.severity = suggestion
-dotnet_diagnostic.CA1310.severity = error
-dotnet_diagnostic.CA1707.severity = suggestion
-dotnet_diagnostic.CA1708.severity = suggestion
-dotnet_diagnostic.CA1711.severity = suggestion
-dotnet_diagnostic.CA1716.severity = suggestion
-dotnet_diagnostic.CA1720.severity = suggestion
-dotnet_diagnostic.CA1725.severity = suggestion
-dotnet_diagnostic.CA1805.severity = suggestion
-dotnet_diagnostic.CA1816.severity = suggestion
-dotnet_diagnostic.CA1822.severity = suggestion
-dotnet_diagnostic.CA1825.severity = error
-dotnet_diagnostic.CA1826.severity = silent
-dotnet_diagnostic.CA1827.severity = error
-dotnet_diagnostic.CA1829.severity = suggestion
-dotnet_diagnostic.CA1834.severity = error
-dotnet_diagnostic.CA1845.severity = suggestion
-dotnet_diagnostic.CA1848.severity = suggestion
-dotnet_diagnostic.CA2016.severity = suggestion
-dotnet_diagnostic.CA2201.severity = error
-dotnet_diagnostic.CA2206.severity = error
-dotnet_diagnostic.CA2208.severity = error
-dotnet_diagnostic.CA2211.severity = error
-dotnet_diagnostic.CA2249.severity = error
-dotnet_diagnostic.CA2251.severity = error
-dotnet_diagnostic.CA2252.severity = none
-dotnet_diagnostic.CA2254.severity = suggestion
-
-dotnet_diagnostic.CS0169.severity = error
-dotnet_diagnostic.CS0219.severity = error
-dotnet_diagnostic.CS1998.severity = error
-dotnet_diagnostic.CS8602.severity = error
-dotnet_diagnostic.CS8604.severity = error
-dotnet_diagnostic.CS8618.severity = error
-dotnet_diagnostic.CS0618.severity = error
-dotnet_diagnostic.CS1998.severity = error
-dotnet_diagnostic.CS4014.severity = error
-dotnet_diagnostic.CS8600.severity = error
-dotnet_diagnostic.CS8603.severity = error
-dotnet_diagnostic.CS8625.severity = error
-
-dotnet_diagnostic.BL0005.severity = suggestion
-
-dotnet_diagnostic.MVC1000.severity = suggestion
-
-dotnet_diagnostic.IDE0055.severity = suggestion # Fix formatting
-dotnet_diagnostic.IDE0023.severity = suggestion # use expression body for operators
-dotnet_diagnostic.IDE0025.severity = suggestion # use expression body for properties
-dotnet_diagnostic.IDE1006.severity = suggestion # Naming rule violation: These words cannot contain lower case characters
-dotnet_diagnostic.IDE0072.severity = suggestion # Populate switch - forces population of all cases even when default specified
-dotnet_diagnostic.IDE0027.severity = suggestion # Use expression body for accessors
-dotnet_diagnostic.IDE0032.severity = suggestion # Use auto property
-dotnet_diagnostic.IDE0007.severity = error # Use var
-dotnet_diagnostic.IDE0160.severity = suggestion # Use block scoped
-dotnet_diagnostic.IDE0011.severity = error # Use braces on if statements
-dotnet_diagnostic.IDE0057.severity = suggestion # substring can be simplified
-dotnet_diagnostic.IDE0004.severity = error # redundant cast
-dotnet_diagnostic.IDE0010.severity = silent # populate switch
-dotnet_diagnostic.IDE0021.severity = silent # expression body for constructors
-dotnet_diagnostic.IDE0022.severity = silent # expression body for methods
-dotnet_diagnostic.IDE0024.severity = silent # expression body for operators
-dotnet_diagnostic.IDE0028.severity = silent
-dotnet_diagnostic.IDE0033.severity = error # prefer tuple name
-dotnet_diagnostic.IDE0040.severity = error # modifiers required
-dotnet_diagnostic.IDE0041.severity = error # simplify null
-dotnet_diagnostic.IDE0042.severity = error # deconstruct variable
-dotnet_diagnostic.IDE0044.severity = error # make field only when possible
-dotnet_diagnostic.IDE0047.severity = suggestion # paratemeter name
-dotnet_diagnostic.IDE0051.severity = error # unused field
-dotnet_diagnostic.IDE0052.severity = error # unused member
-dotnet_diagnostic.IDE0060.severity = suggestion # unused parameters
-dotnet_diagnostic.IDE0066.severity = suggestion # switch expression
-dotnet_diagnostic.IDE0078.severity = suggestion # use pattern matching
-dotnet_diagnostic.IDE0090.severity = suggestion # new can be simplified
-dotnet_diagnostic.IDE0130.severity = suggestion # namespace folder structure
-dotnet_diagnostic.IDE0160.severity = silent # Use block namespaces ARE NOT required
-dotnet_diagnostic.IDE0161.severity = suggestion # Please use file namespaces
-
-##########################################
-# Styles
-##########################################
-
-# camel_case_style - Define the camelCase style
-dotnet_naming_style.camel_case_style.capitalization = camel_case
-# pascal_case_style - Define the PascalCase style
-dotnet_naming_style.pascal_case_style.capitalization = pascal_case
-# constant_case - Define the CONSTANT_CASE style
-dotnet_naming_style.constant_case.capitalization = all_upper
-dotnet_naming_style.constant_case.word_separator = _
-# first_upper_style - The first character must start with an upper-case character
-dotnet_naming_style.first_upper_style.capitalization = first_word_upper
-# prefix_interface_with_i_style - Interfaces must be PascalCase and the first character of an interface must be an 'I'
-dotnet_naming_style.prefix_interface_with_i_style.capitalization = pascal_case
-dotnet_naming_style.prefix_interface_with_i_style.required_prefix = I
-# prefix_type_parameters_with_t_style - Generic Type Parameters must be PascalCase and the first character must be a 'T'
-dotnet_naming_style.prefix_type_parameters_with_t_style.capitalization = pascal_case
-dotnet_naming_style.prefix_type_parameters_with_t_style.required_prefix = T
-# disallowed_style - Anything that has this style applied is marked as disallowed
-dotnet_naming_style.disallowed_style.capitalization  = pascal_case
-dotnet_naming_style.disallowed_style.required_prefix = ____RULE_VIOLATION____
-dotnet_naming_style.disallowed_style.required_suffix = ____RULE_VIOLATION____
-# internal_error_style - This style should never occur... if it does, it indicates a bug in file or in the parser using the file
-dotnet_naming_style.internal_error_style.capitalization  = pascal_case
-dotnet_naming_style.internal_error_style.required_prefix = ____INTERNAL_ERROR____
-dotnet_naming_style.internal_error_style.required_suffix = ____INTERNAL_ERROR____
-
-# prefix_interface_with_i_style - Interfaces must be PascalCase and the first character of an interface must be an 'I'
-dotnet_naming_style.underscore_camel_case_style.capitalization = camel_case
-dotnet_naming_style.underscore_camel_case_style.required_prefix = _
-
-##########################################
-# .NET Design Guideline Field Naming Rules
-# Naming rules for fields follow the .NET Framework design guidelines
-# https://docs.microsoft.com/dotnet/standard/design-guidelines/index
-##########################################
-
-# All public/protected/protected_internal constant fields must be constant_case
-# https://docs.microsoft.com/dotnet/standard/design-guidelines/field
-dotnet_naming_symbols.public_protected_constant_fields_group.applicable_accessibilities = public, protected, protected_internal
-dotnet_naming_symbols.public_protected_constant_fields_group.required_modifiers         = const
-dotnet_naming_symbols.public_protected_constant_fields_group.applicable_kinds           = field
-dotnet_naming_rule.public_protected_constant_fields_must_be_pascal_case_rule.symbols    = public_protected_constant_fields_group
-dotnet_naming_rule.public_protected_constant_fields_must_be_pascal_case_rule.style      = constant_case
-dotnet_naming_rule.public_protected_constant_fields_must_be_pascal_case_rule.severity   = warning
-
-# All public/protected/protected_internal static readonly fields must be constant_case
-# https://docs.microsoft.com/dotnet/standard/design-guidelines/field
-dotnet_naming_symbols.public_protected_static_readonly_fields_group.applicable_accessibilities = public, protected, protected_internal
-dotnet_naming_symbols.public_protected_static_readonly_fields_group.required_modifiers         = static, readonly
-dotnet_naming_symbols.public_protected_static_readonly_fields_group.applicable_kinds           = field
-dotnet_naming_rule.public_protected_static_readonly_fields_must_be_pascal_case_rule.symbols    = public_protected_static_readonly_fields_group
-dotnet_naming_rule.public_protected_static_readonly_fields_must_be_pascal_case_rule.style      = constant_case
-dotnet_naming_rule.public_protected_static_readonly_fields_must_be_pascal_case_rule.severity   = warning
-
-# No other public/protected/protected_internal fields are allowed
-# https://docs.microsoft.com/dotnet/standard/design-guidelines/field
-dotnet_naming_symbols.other_public_protected_fields_group.applicable_accessibilities = public, protected, protected_internal
-dotnet_naming_symbols.other_public_protected_fields_group.applicable_kinds           = field
-dotnet_naming_rule.other_public_protected_fields_disallowed_rule.symbols             = other_public_protected_fields_group
-dotnet_naming_rule.other_public_protected_fields_disallowed_rule.style               = disallowed_style
-dotnet_naming_rule.other_public_protected_fields_disallowed_rule.severity            = error
-
-##########################################
-# StyleCop Field Naming Rules
-# Naming rules for fields follow the StyleCop analyzers
-# This does not override any rules using disallowed_style above
-# https://github.com/DotNetAnalyzers/StyleCopAnalyzers
-##########################################
-
-# All constant fields must be constant_case
-# https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1303.md
-dotnet_naming_symbols.stylecop_constant_fields_group.applicable_accessibilities = public, internal, protected_internal, protected, private_protected, private
-dotnet_naming_symbols.stylecop_constant_fields_group.required_modifiers         = const
-dotnet_naming_symbols.stylecop_constant_fields_group.applicable_kinds           = field
-dotnet_naming_rule.stylecop_constant_fields_must_be_pascal_case_rule.symbols    = stylecop_constant_fields_group
-dotnet_naming_rule.stylecop_constant_fields_must_be_pascal_case_rule.style      = constant_case
-dotnet_naming_rule.stylecop_constant_fields_must_be_pascal_case_rule.severity   = warning
-
-# All static readonly fields must be constant_case
-# https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1311.md
-dotnet_naming_symbols.stylecop_static_readonly_fields_group.applicable_accessibilities = public, internal, protected_internal, protected, private_protected, private
-dotnet_naming_symbols.stylecop_static_readonly_fields_group.required_modifiers         = static, readonly
-dotnet_naming_symbols.stylecop_static_readonly_fields_group.applicable_kinds           = field
-dotnet_naming_rule.stylecop_static_readonly_fields_must_be_pascal_case_rule.symbols    = stylecop_static_readonly_fields_group
-dotnet_naming_rule.stylecop_static_readonly_fields_must_be_pascal_case_rule.style      = constant_case
-dotnet_naming_rule.stylecop_static_readonly_fields_must_be_pascal_case_rule.severity   = warning
-
-# No non-private instance fields are allowed
-# https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1401.md
-dotnet_naming_symbols.stylecop_fields_must_be_private_group.applicable_accessibilities = public, internal, protected_internal, protected, private_protected
-dotnet_naming_symbols.stylecop_fields_must_be_private_group.applicable_kinds           = field
-dotnet_naming_rule.stylecop_instance_fields_must_be_private_rule.symbols               = stylecop_fields_must_be_private_group
-dotnet_naming_rule.stylecop_instance_fields_must_be_private_rule.style                 = disallowed_style
-dotnet_naming_rule.stylecop_instance_fields_must_be_private_rule.severity              = error
-
-# Private fields must be camelCase
-# https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1306.md
-dotnet_naming_symbols.stylecop_private_fields_group.applicable_accessibilities = private
-dotnet_naming_symbols.stylecop_private_fields_group.applicable_kinds           = field
-dotnet_naming_rule.stylecop_private_fields_must_be_camel_case_rule.symbols     = stylecop_private_fields_group
-dotnet_naming_rule.stylecop_private_fields_must_be_camel_case_rule.style       = underscore_camel_case_style
-dotnet_naming_rule.stylecop_private_fields_must_be_camel_case_rule.severity    = warning
-
-# Local variables must be camelCase
-# https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1312.md
-dotnet_naming_symbols.stylecop_local_fields_group.applicable_accessibilities = local
-dotnet_naming_symbols.stylecop_local_fields_group.applicable_kinds           = local
-dotnet_naming_rule.stylecop_local_fields_must_be_camel_case_rule.symbols     = stylecop_local_fields_group
-dotnet_naming_rule.stylecop_local_fields_must_be_camel_case_rule.style       = camel_case_style
-dotnet_naming_rule.stylecop_local_fields_must_be_camel_case_rule.severity    = warning
-
-# This rule should never fire.  However, it's included for at least two purposes:
-# First, it helps to understand, reason about, and root-case certain types of issues, such as bugs in .editorconfig parsers.
-# Second, it helps to raise immediate awareness if a new field type is added (as occurred recently in C#).
-dotnet_naming_symbols.sanity_check_uncovered_field_case_group.applicable_accessibilities = *
-dotnet_naming_symbols.sanity_check_uncovered_field_case_group.applicable_kinds           = field
-dotnet_naming_rule.sanity_check_uncovered_field_case_rule.symbols  = sanity_check_uncovered_field_case_group
-dotnet_naming_rule.sanity_check_uncovered_field_case_rule.style    = internal_error_style
-dotnet_naming_rule.sanity_check_uncovered_field_case_rule.severity = error
-
-
-##########################################
-# Other Naming Rules
-##########################################
-
-# All of the following must be PascalCase:
-# - Namespaces
-#   https://docs.microsoft.com/dotnet/standard/design-guidelines/names-of-namespaces
-#   https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1300.md
-# - Classes and Enumerations
-#   https://docs.microsoft.com/dotnet/standard/design-guidelines/names-of-classes-structs-and-interfaces
-#   https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/SA1300.md
-# - Delegates
-#   https://docs.microsoft.com/dotnet/standard/design-guidelines/names-of-classes-structs-and-interfaces#names-of-common-types
-# - Constructors, Properties, Events, Methods
-#   https://docs.microsoft.com/dotnet/standard/design-guidelines/names-of-type-members
-dotnet_naming_symbols.element_group.applicable_kinds = namespace, class, enum, struct, delegate, event, method, property
-dotnet_naming_rule.element_rule.symbols              = element_group
-dotnet_naming_rule.element_rule.style                = pascal_case_style
-dotnet_naming_rule.element_rule.severity             = warning
-
-# Interfaces use PascalCase and are prefixed with uppercase 'I'
-# https://docs.microsoft.com/dotnet/standard/design-guidelines/names-of-classes-structs-and-interfaces
-dotnet_naming_symbols.interface_group.applicable_kinds = interface
-dotnet_naming_rule.interface_rule.symbols              = interface_group
-dotnet_naming_rule.interface_rule.style                = prefix_interface_with_i_style
-dotnet_naming_rule.interface_rule.severity             = warning
-
-# Generics Type Parameters use PascalCase and are prefixed with uppercase 'T'
-# https://docs.microsoft.com/dotnet/standard/design-guidelines/names-of-classes-structs-and-interfaces
-dotnet_naming_symbols.type_parameter_group.applicable_kinds = type_parameter
-dotnet_naming_rule.type_parameter_rule.symbols              = type_parameter_group
-dotnet_naming_rule.type_parameter_rule.style                = prefix_type_parameters_with_t_style
-dotnet_naming_rule.type_parameter_rule.severity             = warning
-
-# Function parameters use camelCase
-# https://docs.microsoft.com/dotnet/standard/design-guidelines/naming-parameters
-dotnet_naming_symbols.parameters_group.applicable_kinds = parameter
-dotnet_naming_rule.parameters_rule.symbols              = parameters_group
-dotnet_naming_rule.parameters_rule.style                = camel_case_style
-dotnet_naming_rule.parameters_rule.severity             = warning
-
-##########################################
-# License
-##########################################
-# The following applies as to the .editorconfig file ONLY, and is
-# included below for reference, per the requirements of the license
-# corresponding to this .editorconfig file.
-# See: https://github.com/RehanSaeed/EditorConfig
-#
-# MIT License
-#
-# Copyright (c) 2017-2019 Muhammad Rehan Saeed
-# Copyright (c) 2019 Henry Gabryjelski
-#
-# Permission is hereby granted, free of charge, to any
-# person obtaining a copy of this software and associated
-# documentation files (the "Software"), to deal in the
-# Software without restriction, including without limitation
-# the rights to use, copy, modify, merge, publish, distribute,
-# sublicense, and/or sell copies of the Software, and to permit
-# persons to whom the Software is furnished to do so, subject
-# to the following conditions:
-#
-# The above copyright notice and this permission notice shall be
-# included in all copies or substantial portions of the Software.
-#
-# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
-# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
-# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
-# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
-# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
-# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
-# OTHER DEALINGS IN THE SOFTWARE.
-##########################################

.github/dependabot.yml

@@ -1,6 +0,0 @@
-version: 2
-updates:
-  - package-ecosystem: "github-actions" # search for actions - there are other options available
-    directory: "/" # search in .github/workflows under root `/`
-    schedule:
-      interval: "weekly" # check for action update every week

.github/workflows/dotnetcore.yml

@@ -9,12 +9,12 @@ jobs:
         os: [windows-latest, ubuntu-latest]
 
     steps:
-    - uses: actions/checkout@v3
-    - uses: actions/setup-dotnet@v2
+    - uses: actions/checkout@v1
+    - uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 6.0.x
+        dotnet-version: 5.0.401
     - run: dotnet run -p build/build.csproj
-    - uses: actions/upload-artifact@v3
+    - uses: actions/upload-artifact@v2
       with:
         name: ${{ matrix.os }}-sharpcompress.nupkg
         path: artifacts/*

.gitignore

@@ -18,4 +18,3 @@ tools
 
 .DS_Store
 *.snupkg
-/tests/TestArchives/6d23a38c-f064-4ef1-ad89-b942396f53b9/Scratch

README.md

@@ -182,8 +182,6 @@ I'm always looking for help or ideas. Please submit code or email with ideas. Un
 
 XZ implementation based on: https://github.com/sambott/XZ.NET by @sambott
 
-XZ BCJ filters support contributed by Louis-Michel Bergeron, on behalf of aDolus Technology Inc. - 2022
-
 7Zip implementation based on: https://code.google.com/p/managed-lzma/
 
 LICENSE

build/Program.cs

@@ -6,78 +6,78 @@ using GlobExpressions;
 using static Bullseye.Targets;
 using static SimpleExec.Command;
 
-const string Clean = "clean";
-const string Format = "format";
-const string Build = "build";
-const string Test = "test";
-const string Publish = "publish";
+class Program
+{
+    private const string Clean = "clean";
+    private const string Format = "format";
+    private const string Build = "build";
+    private const string Test = "test";
+    private const string Publish = "publish";
 
-Target(Clean,
-       ForEach("**/bin", "**/obj"),
-       dir =>
-       {
-           IEnumerable<string> GetDirectories(string d)
-           {
-               return Glob.Directories(".", d);
-           }
+    static void Main(string[] args)
+    {
+        Target(Clean,
+            ForEach("**/bin", "**/obj"),
+            dir =>
+            {
+                IEnumerable<string> GetDirectories(string d)
+                {
+                    return Glob.Directories(".", d);
+                }
 
-           void RemoveDirectory(string d)
-           {
-               if (Directory.Exists(d))
+                void RemoveDirectory(string d)
+                {
+                    if (Directory.Exists(d))
+                    {
+                        Console.WriteLine(d);
+                        Directory.Delete(d, true);
+                    }
+                }
+
+                foreach (var d in GetDirectories(dir))
+                {
+                    RemoveDirectory(d);
+                }
+            });
+
+        Target(Format, () =>
+        {
+            Run("dotnet", "tool restore");
+            Run("dotnet", "format --check");
+        });
+
+        Target(Build, DependsOn(Format),
+               framework =>
                {
-                   Console.WriteLine(d);
-                   Directory.Delete(d, true);
-               }
-           }
+                   Run("dotnet", "build src/SharpCompress/SharpCompress.csproj -c Release");
+               });
 
-           foreach (var d in GetDirectories(dir))
-           {
-               RemoveDirectory(d);
-           }
-       });
+        Target(Test, DependsOn(Build), ForEach("net5.0", "net461"),
+               framework =>
+               {
+                   IEnumerable<string> GetFiles(string d)
+                   {
+                       return Glob.Files(".", d);
+                   }
+                   if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && framework == "net461")
+                   {
+                       return;
+                   }
 
-Target(Format,
-       () =>
-       {
-           Run("dotnet", "tool restore");
-           Run("dotnet", "format --check");
-       });
+                   foreach (var file in GetFiles("**/*.Test.csproj"))
+                   {
+                       Run("dotnet", $"test {file} -c Release -f {framework}");
+                   }
+               });
 
-Target(Build,
-       DependsOn(Format),
-       framework =>
-       {
-           Run("dotnet", "build src/SharpCompress/SharpCompress.csproj -c Release");
-       });
+        Target(Publish, DependsOn(Test),
+               () =>
+               {
+                   Run("dotnet", "pack src/SharpCompress/SharpCompress.csproj -c Release -o artifacts/");
+               });
 
-Target(Test,
-       DependsOn(Build),
-       ForEach("net6.0", "net461"),
-       framework =>
-       {
-           IEnumerable<string> GetFiles(string d)
-           {
-               return Glob.Files(".", d);
-           }
+        Target("default", DependsOn(Publish), () => Console.WriteLine("Done!"));
 
-           if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && framework == "net461")
-           {
-               return;
-           }
-
-           foreach (var file in GetFiles("**/*.Test.csproj"))
-           {
-               Run("dotnet", $"test {file} -c Release -f {framework}");
-           }
-       });
-
-Target(Publish,
-       DependsOn(Test),
-       () =>
-       {
-           Run("dotnet", "pack src/SharpCompress/SharpCompress.csproj -c Release -o artifacts/");
-       });
-
-Target("default", DependsOn(Publish), () => Console.WriteLine("Done!"));
-
-await RunTargetsAndExitAsync(args);
+        RunTargetsAndExit(args);
+    }
+}

build/build.csproj

@@ -2,13 +2,13 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net5.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Bullseye" Version="4.0.0" />
-    <PackageReference Include="Glob" Version="1.1.9" />
-    <PackageReference Include="SimpleExec" Version="10.0.0" />
+    <PackageReference Include="Bullseye" Version="3.8.0" />
+    <PackageReference Include="Glob" Version="1.1.8" />
+    <PackageReference Include="SimpleExec" Version="8.0.0" />
   </ItemGroup>
 
 </Project>

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "6.0.200",
+    "version": "5.0.300",
     "rollForward": "latestFeature"
   }
 }

src/SharpCompress/Algorithms/Adler32.cs

@@ -1,420 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Apache License, Version 2.0.
-
-#if !NETSTANDARD2_0 && !NETSTANDARD2_1 && !NETFRAMEWORK
-#define SUPPORTS_RUNTIME_INTRINSICS
-#define SUPPORTS_HOTPATH
-#endif
-
-using System;
-using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
-#if SUPPORTS_RUNTIME_INTRINSICS
-using System.Runtime.Intrinsics;
-using System.Runtime.Intrinsics.X86;
-#endif
-
-#pragma warning disable IDE0007 // Use implicit type
-namespace SharpCompress.Algorithms
-{
-    /// <summary>
-    /// Calculates the 32 bit Adler checksum of a given buffer according to
-    /// RFC 1950. ZLIB Compressed Data Format Specification version 3.3)
-    /// </summary>
-    internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/blob/main/src/ImageSharp/Compression/Zlib/Adler32.cs
-    {
-        /// <summary>
-        /// Global inlining options. Helps temporarily disable inlining for better profiler output.
-        /// </summary>
-        private static class InliningOptions // From https://github.com/SixLabors/ImageSharp/blob/main/src/ImageSharp/Common/Helpers/InliningOptions.cs
-        {
-            /// <summary>
-            /// <see cref="MethodImplOptions.AggressiveInlining"/> regardless of the build conditions.
-            /// </summary>
-            public const MethodImplOptions AlwaysInline = MethodImplOptions.AggressiveInlining;
-#if PROFILING
-            public const MethodImplOptions HotPath = MethodImplOptions.NoInlining;
-            public const MethodImplOptions ShortMethod = MethodImplOptions.NoInlining;
-#else
-#if SUPPORTS_HOTPATH
-            public const MethodImplOptions HotPath = MethodImplOptions.AggressiveOptimization;
-#else
-            public const MethodImplOptions HotPath = MethodImplOptions.AggressiveInlining;
-#endif
-            public const MethodImplOptions ShortMethod = MethodImplOptions.AggressiveInlining;
-#endif
-            public const MethodImplOptions ColdPath = MethodImplOptions.NoInlining;
-        }
-
-#if SUPPORTS_RUNTIME_INTRINSICS
-        /// <summary>
-        /// Provides optimized static methods for trigonometric, logarithmic,
-        /// and other common mathematical functions.
-        /// </summary>
-        private static class Numerics // From https://github.com/SixLabors/ImageSharp/blob/main/src/ImageSharp/Common/Helpers/Numerics.cs
-        {
-            /// <summary>
-            /// Reduces elements of the vector into one sum.
-            /// </summary>
-            /// <param name="accumulator">The accumulator to reduce.</param>
-            /// <returns>The sum of all elements.</returns>
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public static int ReduceSum(Vector256<int> accumulator)
-            {
-                // Add upper lane to lower lane.
-                Vector128<int> vsum = Sse2.Add(accumulator.GetLower(), accumulator.GetUpper());
-
-                // Add odd to even.
-                vsum = Sse2.Add(vsum, Sse2.Shuffle(vsum, 0b_11_11_01_01));
-
-                // Add high to low.
-                vsum = Sse2.Add(vsum, Sse2.Shuffle(vsum, 0b_11_10_11_10));
-
-                return Sse2.ConvertToInt32(vsum);
-            }
-
-            /// <summary>
-            /// Reduces even elements of the vector into one sum.
-            /// </summary>
-            /// <param name="accumulator">The accumulator to reduce.</param>
-            /// <returns>The sum of even elements.</returns>
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public static int EvenReduceSum(Vector256<int> accumulator)
-            {
-                Vector128<int> vsum = Sse2.Add(accumulator.GetLower(), accumulator.GetUpper()); // add upper lane to lower lane
-                vsum = Sse2.Add(vsum, Sse2.Shuffle(vsum, 0b_11_10_11_10));                      // add high to low
-
-                // Vector128<int>.ToScalar() isn't optimized pre-net5.0 https://github.com/dotnet/runtime/pull/37882
-                return Sse2.ConvertToInt32(vsum);
-            }
-        }
-#endif
-
-        /// <summary>
-        /// The default initial seed value of a Adler32 checksum calculation.
-        /// </summary>
-        public const uint SeedValue = 1U;
-
-        // Largest prime smaller than 65536
-        private const uint BASE = 65521;
-
-        // NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
-        private const uint NMAX = 5552;
-
-#if SUPPORTS_RUNTIME_INTRINSICS
-        private const int MinBufferSize = 64;
-
-        private const int BlockSize = 1 << 5;
-
-        // The C# compiler emits this as a compile-time constant embedded in the PE file.
-        private static ReadOnlySpan<byte> Tap1Tap2 => new byte[]
-        {
-            32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, // tap1
-            16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 // tap2
-        };
-#endif
-
-        /// <summary>
-        /// Calculates the Adler32 checksum with the bytes taken from the span.
-        /// </summary>
-        /// <param name="buffer">The readonly span of bytes.</param>
-        /// <returns>The <see cref="uint"/>.</returns>
-        [MethodImpl(InliningOptions.ShortMethod)]
-        public static uint Calculate(ReadOnlySpan<byte> buffer)
-            => Calculate(SeedValue, buffer);
-
-        /// <summary>
-        /// Calculates the Adler32 checksum with the bytes taken from the span and seed.
-        /// </summary>
-        /// <param name="adler">The input Adler32 value.</param>
-        /// <param name="buffer">The readonly span of bytes.</param>
-        /// <returns>The <see cref="uint"/>.</returns>
-        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
-        public static uint Calculate(uint adler, ReadOnlySpan<byte> buffer)
-        {
-            if (buffer.IsEmpty)
-            {
-                return adler;
-            }
-
-#if SUPPORTS_RUNTIME_INTRINSICS
-            if (Avx2.IsSupported && buffer.Length >= MinBufferSize)
-            {
-                return CalculateAvx2(adler, buffer);
-            }
-
-            if (Ssse3.IsSupported && buffer.Length >= MinBufferSize)
-            {
-                return CalculateSse(adler, buffer);
-            }
-
-            return CalculateScalar(adler, buffer);
-#else
-            return CalculateScalar(adler, buffer);
-#endif
-        }
-
-        // Based on https://github.com/chromium/chromium/blob/master/third_party/zlib/adler32_simd.c
-#if SUPPORTS_RUNTIME_INTRINSICS
-        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
-        private static unsafe uint CalculateSse(uint adler, ReadOnlySpan<byte> buffer)
-        {
-            uint s1 = adler & 0xFFFF;
-            uint s2 = (adler >> 16) & 0xFFFF;
-
-            // Process the data in blocks.
-            uint length = (uint)buffer.Length;
-            uint blocks = length / BlockSize;
-            length -= blocks * BlockSize;
-
-            fixed (byte* bufferPtr = &MemoryMarshal.GetReference(buffer))
-            {
-                fixed (byte* tapPtr = &MemoryMarshal.GetReference(Tap1Tap2))
-                {
-                    byte* localBufferPtr = bufferPtr;
-
-                    // _mm_setr_epi8 on x86
-                    Vector128<sbyte> tap1 = Sse2.LoadVector128((sbyte*)tapPtr);
-                    Vector128<sbyte> tap2 = Sse2.LoadVector128((sbyte*)(tapPtr + 0x10));
-                    Vector128<byte> zero = Vector128<byte>.Zero;
-                    var ones = Vector128.Create((short)1);
-
-                    while (blocks > 0)
-                    {
-                        uint n = NMAX / BlockSize;  /* The NMAX constraint. */
-                        if (n > blocks)
-                        {
-                            n = blocks;
-                        }
-
-                        blocks -= n;
-
-                        // Process n blocks of data. At most NMAX data bytes can be
-                        // processed before s2 must be reduced modulo BASE.
-                        Vector128<uint> v_ps = Vector128.CreateScalar(s1 * n);
-                        Vector128<uint> v_s2 = Vector128.CreateScalar(s2);
-                        Vector128<uint> v_s1 = Vector128<uint>.Zero;
-
-                        do
-                        {
-                            // Load 32 input bytes.
-                            Vector128<byte> bytes1 = Sse3.LoadDquVector128(localBufferPtr);
-                            Vector128<byte> bytes2 = Sse3.LoadDquVector128(localBufferPtr + 0x10);
-
-                            // Add previous block byte sum to v_ps.
-                            v_ps = Sse2.Add(v_ps, v_s1);
-
-                            // Horizontally add the bytes for s1, multiply-adds the
-                            // bytes by [ 32, 31, 30, ... ] for s2.
-                            v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes1, zero).AsUInt32());
-                            Vector128<short> mad1 = Ssse3.MultiplyAddAdjacent(bytes1, tap1);
-                            v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad1, ones).AsUInt32());
-
-                            v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes2, zero).AsUInt32());
-                            Vector128<short> mad2 = Ssse3.MultiplyAddAdjacent(bytes2, tap2);
-                            v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad2, ones).AsUInt32());
-
-                            localBufferPtr += BlockSize;
-                        }
-                        while (--n > 0);
-
-                        v_s2 = Sse2.Add(v_s2, Sse2.ShiftLeftLogical(v_ps, 5));
-
-                        // Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
-                        const byte S2301 = 0b1011_0001;  // A B C D -> B A D C
-                        const byte S1032 = 0b0100_1110;  // A B C D -> C D A B
-
-                        v_s1 = Sse2.Add(v_s1, Sse2.Shuffle(v_s1, S1032));
-
-                        s1 += v_s1.ToScalar();
-
-                        v_s2 = Sse2.Add(v_s2, Sse2.Shuffle(v_s2, S2301));
-                        v_s2 = Sse2.Add(v_s2, Sse2.Shuffle(v_s2, S1032));
-
-                        s2 = v_s2.ToScalar();
-
-                        // Reduce.
-                        s1 %= BASE;
-                        s2 %= BASE;
-                    }
-
-                    if (length > 0)
-                    {
-                        HandleLeftOver(localBufferPtr, length, ref s1, ref s2);
-                    }
-
-                    return s1 | (s2 << 16);
-                }
-            }
-        }
-
-        // Based on: https://github.com/zlib-ng/zlib-ng/blob/develop/arch/x86/adler32_avx2.c
-        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
-        public static unsafe uint CalculateAvx2(uint adler, ReadOnlySpan<byte> buffer)
-        {
-            uint s1 = adler & 0xFFFF;
-            uint s2 = (adler >> 16) & 0xFFFF;
-            uint length = (uint)buffer.Length;
-
-            fixed (byte* bufferPtr = &MemoryMarshal.GetReference(buffer))
-            {
-                byte* localBufferPtr = bufferPtr;
-
-                Vector256<byte> zero = Vector256<byte>.Zero;
-                var dot3v = Vector256.Create((short)1);
-                var dot2v = Vector256.Create(32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1);
-
-                // Process n blocks of data. At most NMAX data bytes can be
-                // processed before s2 must be reduced modulo BASE.
-                var vs1 = Vector256.CreateScalar(s1);
-                var vs2 = Vector256.CreateScalar(s2);
-
-                while (length >= 32)
-                {
-                    int k = length < NMAX ? (int)length : (int)NMAX;
-                    k -= k % 32;
-                    length -= (uint)k;
-
-                    Vector256<uint> vs10 = vs1;
-                    Vector256<uint> vs3 = Vector256<uint>.Zero;
-
-                    while (k >= 32)
-                    {
-                        // Load 32 input bytes.
-                        Vector256<byte> block = Avx.LoadVector256(localBufferPtr);
-
-                        // Sum of abs diff, resulting in 2 x int32's
-                        Vector256<ushort> vs1sad = Avx2.SumAbsoluteDifferences(block, zero);
-
-                        vs1 = Avx2.Add(vs1, vs1sad.AsUInt32());
-                        vs3 = Avx2.Add(vs3, vs10);
-
-                        // sum 32 uint8s to 16 shorts.
-                        Vector256<short> vshortsum2 = Avx2.MultiplyAddAdjacent(block, dot2v);
-
-                        // sum 16 shorts to 8 uint32s.
-                        Vector256<int> vsum2 = Avx2.MultiplyAddAdjacent(vshortsum2, dot3v);
-
-                        vs2 = Avx2.Add(vsum2.AsUInt32(), vs2);
-                        vs10 = vs1;
-
-                        localBufferPtr += BlockSize;
-                        k -= 32;
-                    }
-
-                    // Defer the multiplication with 32 to outside of the loop.
-                    vs3 = Avx2.ShiftLeftLogical(vs3, 5);
-                    vs2 = Avx2.Add(vs2, vs3);
-
-                    s1 = (uint)Numerics.EvenReduceSum(vs1.AsInt32());
-                    s2 = (uint)Numerics.ReduceSum(vs2.AsInt32());
-
-                    s1 %= BASE;
-                    s2 %= BASE;
-
-                    vs1 = Vector256.CreateScalar(s1);
-                    vs2 = Vector256.CreateScalar(s2);
-                }
-
-                if (length > 0)
-                {
-                    HandleLeftOver(localBufferPtr, length, ref s1, ref s2);
-                }
-
-                return s1 | (s2 << 16);
-            }
-        }
-
-        private static unsafe void HandleLeftOver(byte* localBufferPtr, uint length, ref uint s1, ref uint s2)
-        {
-            if (length >= 16)
-            {
-                s2 += s1 += localBufferPtr[0];
-                s2 += s1 += localBufferPtr[1];
-                s2 += s1 += localBufferPtr[2];
-                s2 += s1 += localBufferPtr[3];
-                s2 += s1 += localBufferPtr[4];
-                s2 += s1 += localBufferPtr[5];
-                s2 += s1 += localBufferPtr[6];
-                s2 += s1 += localBufferPtr[7];
-                s2 += s1 += localBufferPtr[8];
-                s2 += s1 += localBufferPtr[9];
-                s2 += s1 += localBufferPtr[10];
-                s2 += s1 += localBufferPtr[11];
-                s2 += s1 += localBufferPtr[12];
-                s2 += s1 += localBufferPtr[13];
-                s2 += s1 += localBufferPtr[14];
-                s2 += s1 += localBufferPtr[15];
-
-                localBufferPtr += 16;
-                length -= 16;
-            }
-
-            while (length-- > 0)
-            {
-                s2 += s1 += *localBufferPtr++;
-            }
-
-            if (s1 >= BASE)
-            {
-                s1 -= BASE;
-            }
-
-            s2 %= BASE;
-        }
-#endif
-
-        [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
-        private static unsafe uint CalculateScalar(uint adler, ReadOnlySpan<byte> buffer)
-        {
-            uint s1 = adler & 0xFFFF;
-            uint s2 = (adler >> 16) & 0xFFFF;
-            uint k;
-
-            fixed (byte* bufferPtr = buffer)
-            {
-                var localBufferPtr = bufferPtr;
-                uint length = (uint)buffer.Length;
-
-                while (length > 0)
-                {
-                    k = length < NMAX ? length : NMAX;
-                    length -= k;
-
-                    while (k >= 16)
-                    {
-                        s2 += s1 += localBufferPtr[0];
-                        s2 += s1 += localBufferPtr[1];
-                        s2 += s1 += localBufferPtr[2];
-                        s2 += s1 += localBufferPtr[3];
-                        s2 += s1 += localBufferPtr[4];
-                        s2 += s1 += localBufferPtr[5];
-                        s2 += s1 += localBufferPtr[6];
-                        s2 += s1 += localBufferPtr[7];
-                        s2 += s1 += localBufferPtr[8];
-                        s2 += s1 += localBufferPtr[9];
-                        s2 += s1 += localBufferPtr[10];
-                        s2 += s1 += localBufferPtr[11];
-                        s2 += s1 += localBufferPtr[12];
-                        s2 += s1 += localBufferPtr[13];
-                        s2 += s1 += localBufferPtr[14];
-                        s2 += s1 += localBufferPtr[15];
-
-                        localBufferPtr += 16;
-                        k -= 16;
-                    }
-
-                    while (k-- > 0)
-                    {
-                        s2 += s1 += *localBufferPtr++;
-                    }
-
-                    s1 %= BASE;
-                    s2 %= BASE;
-                }
-
-                return (s2 << 16) | s1;
-            }
-        }
-    }
-}

src/SharpCompress/Algorithms/Alder32.cs

@@ -0,0 +1,280 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the GNU Affero General Public License, Version 3.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+#if !NETSTANDARD2_0 && !NETSTANDARD2_1 && !NETFRAMEWORK
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+#endif
+
+namespace SharpCompress.Algorithms
+{
+    /// <summary>
+    /// Calculates the 32 bit Adler checksum of a given buffer according to
+    /// RFC 1950. ZLIB Compressed Data Format Specification version 3.3)
+    /// </summary>
+    internal static class Adler32
+    {
+        /// <summary>
+        /// The default initial seed value of a Adler32 checksum calculation.
+        /// </summary>
+        public const uint SeedValue = 1U;
+
+#if !NETSTANDARD2_0 && !NETSTANDARD2_1 && !NETFRAMEWORK
+        private const int MinBufferSize = 64;
+#endif
+
+        // Largest prime smaller than 65536
+        private const uint BASE = 65521;
+
+        // NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
+        private const uint NMAX = 5552;
+
+        /// <summary>
+        /// Calculates the Adler32 checksum with the bytes taken from the span.
+        /// </summary>
+        /// <param name="buffer">The readonly span of bytes.</param>
+        /// <returns>The <see cref="uint"/>.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static uint Calculate(ReadOnlySpan<byte> buffer)
+        {
+            return Calculate(SeedValue, buffer);
+        }
+
+        /// <summary>
+        /// Calculates the Adler32 checksum with the bytes taken from the span and seed.
+        /// </summary>
+        /// <param name="adler">The input Adler32 value.</param>
+        /// <param name="buffer">The readonly span of bytes.</param>
+        /// <returns>The <see cref="uint"/>.</returns>
+        public static uint Calculate(uint adler, ReadOnlySpan<byte> buffer)
+        {
+#if !NETSTANDARD2_0 && !NETSTANDARD2_1 && !NETFRAMEWORK
+            if (Sse3.IsSupported && buffer.Length >= MinBufferSize)
+            {
+                return CalculateSse(adler, buffer);
+            }
+
+            return CalculateScalar(adler, buffer);
+#else
+            return CalculateScalar(adler, buffer);
+#endif
+        }
+
+        // Based on https://github.com/chromium/chromium/blob/master/third_party/zlib/adler32_simd.c
+#if !NETSTANDARD2_0 && !NETSTANDARD2_1 && !NETFRAMEWORK
+        private static unsafe uint CalculateSse(uint adler, ReadOnlySpan<byte> buffer)
+        {
+            uint s1 = adler & 0xFFFF;
+            uint s2 = (adler >> 16) & 0xFFFF;
+
+            // Process the data in blocks.
+            const int BLOCK_SIZE = 1 << 5;
+
+            uint length = (uint)buffer.Length;
+            uint blocks = length / BLOCK_SIZE;
+            length -= blocks * BLOCK_SIZE;
+
+            int index = 0;
+            fixed (byte* bufferPtr = &buffer[0])
+            {
+                index += (int)blocks * BLOCK_SIZE;
+                var localBufferPtr = bufferPtr;
+
+                // _mm_setr_epi8 on x86
+                var tap1 = Vector128.Create(32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17);
+                var tap2 = Vector128.Create(16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1);
+                Vector128<byte> zero = Vector128<byte>.Zero;
+                var ones = Vector128.Create((short)1);
+
+                while (blocks > 0)
+                {
+                    uint n = NMAX / BLOCK_SIZE;  /* The NMAX constraint. */
+                    if (n > blocks)
+                    {
+                        n = blocks;
+                    }
+
+                    blocks -= n;
+
+                    // Process n blocks of data. At most NMAX data bytes can be
+                    // processed before s2 must be reduced modulo BASE.
+                    Vector128<int> v_ps = Vector128.CreateScalar(s1 * n).AsInt32();
+                    Vector128<int> v_s2 = Vector128.CreateScalar(s2).AsInt32();
+                    Vector128<int> v_s1 = Vector128<int>.Zero;
+
+                    do
+                    {
+                        // Load 32 input bytes.
+                        Vector128<byte> bytes1 = Sse3.LoadDquVector128(localBufferPtr);
+                        Vector128<byte> bytes2 = Sse3.LoadDquVector128(localBufferPtr + 16);
+
+                        // Add previous block byte sum to v_ps.
+                        v_ps = Sse2.Add(v_ps, v_s1);
+
+                        // Horizontally add the bytes for s1, multiply-adds the
+                        // bytes by [ 32, 31, 30, ... ] for s2.
+                        v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes1, zero).AsInt32());
+                        Vector128<short> mad1 = Ssse3.MultiplyAddAdjacent(bytes1, tap1);
+                        v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad1, ones));
+
+                        v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes2, zero).AsInt32());
+                        Vector128<short> mad2 = Ssse3.MultiplyAddAdjacent(bytes2, tap2);
+                        v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad2, ones));
+
+                        localBufferPtr += BLOCK_SIZE;
+                    }
+                    while (--n > 0);
+
+                    v_s2 = Sse2.Add(v_s2, Sse2.ShiftLeftLogical(v_ps, 5));
+
+                    // Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
+                    const byte S2301 = 0b1011_0001;  // A B C D -> B A D C
+                    const byte S1032 = 0b0100_1110;  // A B C D -> C D A B
+
+                    v_s1 = Sse2.Add(v_s1, Sse2.Shuffle(v_s1, S2301));
+                    v_s1 = Sse2.Add(v_s1, Sse2.Shuffle(v_s1, S1032));
+
+                    s1 += (uint)v_s1.ToScalar();
+
+                    v_s2 = Sse2.Add(v_s2, Sse2.Shuffle(v_s2, S2301));
+                    v_s2 = Sse2.Add(v_s2, Sse2.Shuffle(v_s2, S1032));
+
+                    s2 = (uint)v_s2.ToScalar();
+
+                    // Reduce.
+                    s1 %= BASE;
+                    s2 %= BASE;
+                }
+            }
+
+            ref byte bufferRef = ref MemoryMarshal.GetReference(buffer);
+
+            if (length > 0)
+            {
+                if (length >= 16)
+                {
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    length -= 16;
+                }
+
+                while (length-- > 0)
+                {
+                    s2 += s1 += Unsafe.Add(ref bufferRef, index++);
+                }
+
+                if (s1 >= BASE)
+                {
+                    s1 -= BASE;
+                }
+
+                s2 %= BASE;
+            }
+
+            return s1 | (s2 << 16);
+        }
+#endif
+
+        private static uint CalculateScalar(uint adler, ReadOnlySpan<byte> buffer)
+        {
+            uint s1 = adler & 0xFFFF;
+            uint s2 = (adler >> 16) & 0xFFFF;
+            uint k;
+
+            ref byte bufferRef = ref MemoryMarshal.GetReference<byte>(buffer);
+            uint length = (uint)buffer.Length;
+            int index = 0;
+
+            while (length > 0)
+            {
+                k = length < NMAX ? length : NMAX;
+                length -= k;
+
+                while (k >= 16)
+                {
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    k -= 16;
+                }
+
+                if (k != 0)
+                {
+                    do
+                    {
+                        s1 += Unsafe.Add(ref bufferRef, index++);
+                        s2 += s1;
+                    }
+                    while (--k != 0);
+                }
+
+                s1 %= BASE;
+                s2 %= BASE;
+            }
+
+            return (s2 << 16) | s1;
+        }
+    }
+}

src/SharpCompress/Archives/AbstractArchive.cs

@@ -1,9 +1,8 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using SharpCompress.Common;
-using SharpCompress.IO;
 using SharpCompress.Readers;
 
 namespace SharpCompress.Archives
@@ -24,14 +23,28 @@ namespace SharpCompress.Archives
         protected ReaderOptions ReaderOptions { get; }
 
         private bool disposed;
-        protected SourceStream SrcStream;
 
-        internal AbstractArchive(ArchiveType type, SourceStream srcStream)
+        internal AbstractArchive(ArchiveType type, FileInfo fileInfo, ReaderOptions readerOptions)
         {
             Type = type;
-            ReaderOptions = srcStream.ReaderOptions;
-            SrcStream = srcStream;
-            lazyVolumes = new LazyReadOnlyCollection<TVolume>(LoadVolumes(SrcStream));
+            if (!fileInfo.Exists)
+            {
+                throw new ArgumentException("File does not exist: " + fileInfo.FullName);
+            }
+            ReaderOptions = readerOptions;
+            readerOptions.LeaveStreamOpen = false;
+            lazyVolumes = new LazyReadOnlyCollection<TVolume>(LoadVolumes(fileInfo));
+            lazyEntries = new LazyReadOnlyCollection<TEntry>(LoadEntries(Volumes));
+        }
+
+
+        protected abstract IEnumerable<TVolume> LoadVolumes(FileInfo file);
+
+        internal AbstractArchive(ArchiveType type, IEnumerable<Stream> streams, ReaderOptions readerOptions)
+        {
+            Type = type;
+            ReaderOptions = readerOptions;
+            lazyVolumes = new LazyReadOnlyCollection<TVolume>(LoadVolumes(streams.Select(CheckStreams)));
             lazyEntries = new LazyReadOnlyCollection<TEntry>(LoadEntries(Volumes));
         }
 
@@ -85,7 +98,7 @@ namespace SharpCompress.Archives
         /// </summary>
         public virtual long TotalUncompressSize => Entries.Aggregate(0L, (total, cf) => total + cf.Size);
 
-        protected abstract IEnumerable<TVolume> LoadVolumes(SourceStream srcStream);
+        protected abstract IEnumerable<TVolume> LoadVolumes(IEnumerable<Stream> streams);
         protected abstract IEnumerable<TEntry> LoadEntries(IEnumerable<TVolume> volumes);
 
         IEnumerable<IArchiveEntry> IArchive.Entries => Entries.Cast<IArchiveEntry>();
@@ -98,8 +111,6 @@ namespace SharpCompress.Archives
             {
                 lazyVolumes.ForEach(v => v.Dispose());
                 lazyEntries.GetLoaded().Cast<Entry>().ForEach(x => x.Close());
-                if (SrcStream != null)
-                    SrcStream.Dispose();
                 disposed = true;
             }
         }

src/SharpCompress/Archives/AbstractWritableArchive.cs

@@ -1,9 +1,8 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using SharpCompress.Common;
-using SharpCompress.IO;
 using SharpCompress.Readers;
 using SharpCompress.Writers;
 
@@ -41,8 +40,13 @@ namespace SharpCompress.Archives
         {
         }
 
-        internal AbstractWritableArchive(ArchiveType type, SourceStream srcStream)
-            : base(type, srcStream)
+        internal AbstractWritableArchive(ArchiveType type, Stream stream, ReaderOptions readerFactoryOptions)
+            : base(type, stream.AsEnumerable(), readerFactoryOptions)
+        {
+        }
+
+        internal AbstractWritableArchive(ArchiveType type, FileInfo fileInfo, ReaderOptions readerFactoryOptions)
+            : base(type, fileInfo, readerFactoryOptions)
         {
         }
 

src/SharpCompress/Archives/ArchiveFactory.cs

@@ -1,14 +1,11 @@
-using System;
-using System.Collections.Generic;
+using System;
 using System.IO;
-using System.Linq;
 using SharpCompress.Archives.GZip;
 using SharpCompress.Archives.Rar;
 using SharpCompress.Archives.SevenZip;
 using SharpCompress.Archives.Tar;
 using SharpCompress.Archives.Zip;
 using SharpCompress.Common;
-using SharpCompress.IO;
 using SharpCompress.Readers;
 
 namespace SharpCompress.Archives
@@ -29,25 +26,34 @@ namespace SharpCompress.Archives
                 throw new ArgumentException("Stream should be readable and seekable");
             }
             readerOptions ??= new ReaderOptions();
-
-            ArchiveType? type;
-            IsArchive(stream, out type); //test and reset stream position
-
-            if (type != null)
+            if (ZipArchive.IsZipFile(stream, null))
             {
-                switch (type.Value)
-                {
-                    case ArchiveType.Zip:
-                        return ZipArchive.Open(stream, readerOptions);
-                    case ArchiveType.SevenZip:
-                        return SevenZipArchive.Open(stream, readerOptions);
-                    case ArchiveType.GZip:
-                        return GZipArchive.Open(stream, readerOptions);
-                    case ArchiveType.Rar:
-                        return RarArchive.Open(stream, readerOptions);
-                    case ArchiveType.Tar:
-                        return TarArchive.Open(stream, readerOptions);
-                }
+                stream.Seek(0, SeekOrigin.Begin);
+                return ZipArchive.Open(stream, readerOptions);
+            }
+            stream.Seek(0, SeekOrigin.Begin);
+            if (SevenZipArchive.IsSevenZipFile(stream))
+            {
+                stream.Seek(0, SeekOrigin.Begin);
+                return SevenZipArchive.Open(stream, readerOptions);
+            }
+            stream.Seek(0, SeekOrigin.Begin);
+            if (GZipArchive.IsGZipFile(stream))
+            {
+                stream.Seek(0, SeekOrigin.Begin);
+                return GZipArchive.Open(stream, readerOptions);
+            }
+            stream.Seek(0, SeekOrigin.Begin);
+            if (RarArchive.IsRarFile(stream, readerOptions))
+            {
+                stream.Seek(0, SeekOrigin.Begin);
+                return RarArchive.Open(stream, readerOptions);
+            }
+            stream.Seek(0, SeekOrigin.Begin);
+            if (TarArchive.IsTarFile(stream))
+            {
+                stream.Seek(0, SeekOrigin.Begin);
+                return TarArchive.Open(stream, readerOptions);
             }
             throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip, LZip");
         }
@@ -84,108 +90,30 @@ namespace SharpCompress.Archives
             fileInfo.CheckNotNull(nameof(fileInfo));
             options ??= new ReaderOptions { LeaveStreamOpen = false };
 
-            ArchiveType? type;
-            using (Stream stream = fileInfo.OpenRead())
+            using var stream = fileInfo.OpenRead();
+            if (ZipArchive.IsZipFile(stream, null))
             {
-                IsArchive(stream, out type); //test and reset stream position
-
-                if (type != null)
-                {
-                    switch (type.Value)
-                    {
-                        case ArchiveType.Zip:
-                            return ZipArchive.Open(fileInfo, options);
-                        case ArchiveType.SevenZip:
-                            return SevenZipArchive.Open(fileInfo, options);
-                        case ArchiveType.GZip:
-                            return GZipArchive.Open(fileInfo, options);
-                        case ArchiveType.Rar:
-                            return RarArchive.Open(fileInfo, options);
-                        case ArchiveType.Tar:
-                            return TarArchive.Open(fileInfo, options);
-                    }
-                }
+                return ZipArchive.Open(fileInfo, options);
             }
-            throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip");
-        }
-
-        /// <summary>
-        /// Constructor with IEnumerable FileInfo objects, multi and split support.
-        /// </summary>
-        /// <param name="fileInfos"></param>
-        /// <param name="options"></param>
-        public static IArchive Open(IEnumerable<FileInfo> fileInfos, ReaderOptions? options = null)
-        {
-            fileInfos.CheckNotNull(nameof(fileInfos));
-            FileInfo[] files = fileInfos.ToArray();
-            if (files.Length == 0)
-                throw new InvalidOperationException("No files to open");
-            FileInfo fileInfo = files[0];
-            if (files.Length == 1)
-                return Open(fileInfo, options);
-
-
-            fileInfo.CheckNotNull(nameof(fileInfo));
-            options ??= new ReaderOptions { LeaveStreamOpen = false };
-
-            ArchiveType? type;
-            using (Stream stream = fileInfo.OpenRead())
-                IsArchive(stream, out type); //test and reset stream position
-
-            if (type != null)
+            stream.Seek(0, SeekOrigin.Begin);
+            if (SevenZipArchive.IsSevenZipFile(stream))
             {
-                switch (type.Value)
-                {
-                    case ArchiveType.Zip:
-                        return ZipArchive.Open(files, options);
-                    case ArchiveType.SevenZip:
-                        return SevenZipArchive.Open(files, options);
-                    case ArchiveType.GZip:
-                        return GZipArchive.Open(files, options);
-                    case ArchiveType.Rar:
-                        return RarArchive.Open(files, options);
-                    case ArchiveType.Tar:
-                        return TarArchive.Open(files, options);
-                }
+                return SevenZipArchive.Open(fileInfo, options);
             }
-            throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip");
-        }
-
-        /// <summary>
-        /// Constructor with IEnumerable FileInfo objects, multi and split support.
-        /// </summary>
-        /// <param name="streams"></param>
-        /// <param name="options"></param>
-        public static IArchive Open(IEnumerable<Stream> streams, ReaderOptions? options = null)
-        {
-            streams.CheckNotNull(nameof(streams));
-            if (streams.Count() == 0)
-                throw new InvalidOperationException("No streams");
-            if (streams.Count() == 1)
-                return Open(streams.First(), options);
-
-
-            options ??= new ReaderOptions();
-
-            ArchiveType? type;
-            using (Stream stream = streams.First())
-                IsArchive(stream, out type); //test and reset stream position
-
-            if (type != null)
+            stream.Seek(0, SeekOrigin.Begin);
+            if (GZipArchive.IsGZipFile(stream))
             {
-                switch (type.Value)
-                {
-                    case ArchiveType.Zip:
-                        return ZipArchive.Open(streams, options);
-                    case ArchiveType.SevenZip:
-                        return SevenZipArchive.Open(streams, options);
-                    case ArchiveType.GZip:
-                        return GZipArchive.Open(streams, options);
-                    case ArchiveType.Rar:
-                        return RarArchive.Open(streams, options);
-                    case ArchiveType.Tar:
-                        return TarArchive.Open(streams, options);
-                }
+                return GZipArchive.Open(fileInfo, options);
+            }
+            stream.Seek(0, SeekOrigin.Begin);
+            if (RarArchive.IsRarFile(stream, options))
+            {
+                return RarArchive.Open(fileInfo, options);
+            }
+            stream.Seek(0, SeekOrigin.Begin);
+            if (TarArchive.IsTarFile(stream))
+            {
+                return TarArchive.Open(fileInfo, options);
             }
             throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip");
         }
@@ -202,95 +130,5 @@ namespace SharpCompress.Archives
                 entry.WriteToDirectory(destinationDirectory, options);
             }
         }
-
-        public static bool IsArchive(string filePath, out ArchiveType? type)
-        {
-            filePath.CheckNotNullOrEmpty(nameof(filePath));
-            using (Stream s = File.OpenRead(filePath))
-                return IsArchive(s, out type);
-        }
-
-        private static bool IsArchive(Stream stream, out ArchiveType? type)
-        {
-            type = null;
-            stream.CheckNotNull(nameof(stream));
-
-            if (!stream.CanRead || !stream.CanSeek)
-            {
-                throw new ArgumentException("Stream should be readable and seekable");
-            }
-            if (ZipArchive.IsZipFile(stream, null))
-                type = ArchiveType.Zip;
-            stream.Seek(0, SeekOrigin.Begin);
-            if (type == null)
-            {
-                if (SevenZipArchive.IsSevenZipFile(stream))
-                    type = ArchiveType.SevenZip;
-                stream.Seek(0, SeekOrigin.Begin);
-            }
-            if (type == null)
-            {
-                if (GZipArchive.IsGZipFile(stream))
-                    type = ArchiveType.GZip;
-                stream.Seek(0, SeekOrigin.Begin);
-            }
-            if (type == null)
-            {
-                if (RarArchive.IsRarFile(stream))
-                    type = ArchiveType.Rar;
-                stream.Seek(0, SeekOrigin.Begin);
-            }
-            if (type == null)
-            {
-                if (TarArchive.IsTarFile(stream))
-                    type = ArchiveType.Tar;
-                stream.Seek(0, SeekOrigin.Begin);
-            }
-            if (type == null) //test multipartzip as it could find zips in other non compressed archive types?
-            {
-                if (ZipArchive.IsZipMulti(stream)) //test the zip (last) file of a multipart zip
-                    type = ArchiveType.Zip;
-                stream.Seek(0, SeekOrigin.Begin);
-            }
-
-            return type != null;
-        }
-
-        /// <summary>
-        /// From a passed in archive (zip, rar, 7z, 001), return all parts.
-        /// </summary>
-        /// <param name="part1"></param>
-        /// <returns></returns>
-        public static IEnumerable<string> GetFileParts(string part1)
-        {
-            part1.CheckNotNullOrEmpty(nameof(part1));
-            return GetFileParts(new FileInfo(part1)).Select(a => a.FullName);
-        }
-
-        /// <summary>
-        /// From a passed in archive (zip, rar, 7z, 001), return all parts.
-        /// </summary>
-        /// <param name="part1"></param>
-        /// <returns></returns>
-        public static IEnumerable<FileInfo> GetFileParts(FileInfo part1)
-        {
-            part1.CheckNotNull(nameof(part1));
-            yield return part1;
-            int i = 1;
-
-            FileInfo? part = RarArchiveVolumeFactory.GetFilePart(i++, part1);
-            if (part != null)
-            {
-                yield return part;
-                while ((part = RarArchiveVolumeFactory.GetFilePart(i++, part1)) != null) //tests split too
-                    yield return part;
-            }
-            else
-            {
-                i = 1;
-                while ((part = ZipArchiveVolumeFactory.GetFilePart(i++, part1)) != null) //tests split too
-                    yield return part;
-            }
-        }
     }
 }

src/SharpCompress/Archives/ArchiveVolumeFactory.cs

@@ -1,29 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.IO;
-using SharpCompress.Readers;
-using System.Linq;
-using System.Text;
-using SharpCompress.Common.Rar.Headers;
-using System.Text.RegularExpressions;
-
-namespace SharpCompress.Archives
-{
-    internal abstract class ArchiveVolumeFactory
-    {
-        internal static FileInfo? GetFilePart(int index, FileInfo part1) //base the name on the first part
-        {
-            FileInfo? item = null;
-
-            //split 001, 002 ...
-            Match m = Regex.Match(part1.Name, @"^(.*\.)([0-9]+)$", RegexOptions.IgnoreCase);
-            if (m.Success)
-                item = new FileInfo(Path.Combine(part1.DirectoryName!, String.Concat(m.Groups[1].Value, (index + 1).ToString().PadLeft(m.Groups[2].Value.Length, '0'))));
-
-            if (item != null && item.Exists)
-                return item;
-            return null;
-        }
-
-    }
-}

src/SharpCompress/Archives/GZip/GZipArchive.cs

@@ -1,10 +1,9 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using SharpCompress.Common;
 using SharpCompress.Common.GZip;
-using SharpCompress.IO;
 using SharpCompress.Readers;
 using SharpCompress.Readers.GZip;
 using SharpCompress.Writers;
@@ -33,31 +32,7 @@ namespace SharpCompress.Archives.GZip
         public static GZipArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            return new GZipArchive(new SourceStream(fileInfo, i => ArchiveVolumeFactory.GetFilePart(i, fileInfo), readerOptions ?? new ReaderOptions()));
-        }
-
-        /// <summary>
-        /// Constructor with all file parts passed in
-        /// </summary>
-        /// <param name="fileInfos"></param>
-        /// <param name="readerOptions"></param>
-        public static GZipArchive Open(IEnumerable<FileInfo> fileInfos, ReaderOptions? readerOptions = null)
-        {
-            fileInfos.CheckNotNull(nameof(fileInfos));
-            FileInfo[] files = fileInfos.ToArray();
-            return new GZipArchive(new SourceStream(files[0], i => i < files.Length ? files[i] : null, readerOptions ?? new ReaderOptions()));
-        }
-
-        /// <summary>
-        /// Constructor with all stream parts passed in
-        /// </summary>
-        /// <param name="streams"></param>
-        /// <param name="readerOptions"></param>
-        public static GZipArchive Open(IEnumerable<Stream> streams, ReaderOptions? readerOptions = null)
-        {
-            streams.CheckNotNull(nameof(streams));
-            Stream[] strms = streams.ToArray();
-            return new GZipArchive(new SourceStream(strms[0], i => i < strms.Length ? strms[i] : null, readerOptions ?? new ReaderOptions()));
+            return new GZipArchive(fileInfo, readerOptions ?? new ReaderOptions());
         }
 
         /// <summary>
@@ -68,7 +43,7 @@ namespace SharpCompress.Archives.GZip
         public static GZipArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
-            return new GZipArchive(new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions()));
+            return new GZipArchive(stream, readerOptions ?? new ReaderOptions());
         }
 
         public static GZipArchive Create()
@@ -77,20 +52,20 @@ namespace SharpCompress.Archives.GZip
         }
 
         /// <summary>
-        /// Constructor with a SourceStream able to handle FileInfo and Streams.
+        /// Constructor with a FileInfo object to an existing file.
         /// </summary>
-        /// <param name="srcStream"></param>
+        /// <param name="fileInfo"></param>
         /// <param name="options"></param>
-        internal GZipArchive(SourceStream srcStream)
-            : base(ArchiveType.Tar, srcStream)
+        internal GZipArchive(FileInfo fileInfo, ReaderOptions options)
+            : base(ArchiveType.GZip, fileInfo, options)
         {
         }
 
-        protected override IEnumerable<GZipVolume> LoadVolumes(SourceStream srcStream)
+        protected override IEnumerable<GZipVolume> LoadVolumes(FileInfo file)
         {
-            srcStream.LoadAllParts();
-            return srcStream.Streams.Select(a => new GZipVolume(a, ReaderOptions));
+            return new GZipVolume(file, ReaderOptions).AsEnumerable();
         }
+
         public static bool IsGZipFile(string filePath)
         {
             return IsGZipFile(new FileInfo(filePath));
@@ -139,6 +114,16 @@ namespace SharpCompress.Archives.GZip
             return true;
         }
 
+        /// <summary>
+        /// Takes multiple seekable Streams for a multi-part archive
+        /// </summary>
+        /// <param name="stream"></param>
+        /// <param name="options"></param>
+        internal GZipArchive(Stream stream, ReaderOptions options)
+            : base(ArchiveType.GZip, stream, options)
+        {
+        }
+
         internal GZipArchive()
             : base(ArchiveType.GZip)
         {
@@ -175,6 +160,11 @@ namespace SharpCompress.Archives.GZip
             }
         }
 
+        protected override IEnumerable<GZipVolume> LoadVolumes(IEnumerable<Stream> streams)
+        {
+            return new GZipVolume(streams.First(), ReaderOptions).AsEnumerable();
+        }
+
         protected override IEnumerable<GZipArchiveEntry> LoadEntries(IEnumerable<GZipVolume> volumes)
         {
             Stream stream = volumes.Single().Stream;

src/SharpCompress/Archives/Rar/RarArchive.cs

@@ -5,7 +5,6 @@ using SharpCompress.Common;
 using SharpCompress.Common.Rar;
 using SharpCompress.Common.Rar.Headers;
 using SharpCompress.Compressors.Rar;
-using SharpCompress.IO;
 using SharpCompress.Readers;
 using SharpCompress.Readers.Rar;
 
@@ -17,14 +16,28 @@ namespace SharpCompress.Archives.Rar
         internal Lazy<IRarUnpack> UnpackV2017 { get; } = new Lazy<IRarUnpack>(() => new SharpCompress.Compressors.Rar.UnpackV2017.Unpack());
         internal Lazy<IRarUnpack> UnpackV1 { get; } = new Lazy<IRarUnpack>(() => new SharpCompress.Compressors.Rar.UnpackV1.Unpack());
 
+        /// <summary>
+        /// Constructor with a FileInfo object to an existing file.
+        /// </summary>
+        /// <param name="fileInfo"></param>
+        /// <param name="options"></param>
+        internal RarArchive(FileInfo fileInfo, ReaderOptions options)
+            : base(ArchiveType.Rar, fileInfo, options)
+        {
+        }
+
+        protected override IEnumerable<RarVolume> LoadVolumes(FileInfo file)
+        {
+            return RarArchiveVolumeFactory.GetParts(file, ReaderOptions);
+        }
 
         /// <summary>
-        /// Constructor with a SourceStream able to handle FileInfo and Streams.
+        /// Takes multiple seekable Streams for a multi-part archive
         /// </summary>
-        /// <param name="srcStream"></param>
+        /// <param name="streams"></param>
         /// <param name="options"></param>
-        internal RarArchive(SourceStream srcStream)
-            : base(ArchiveType.Rar, srcStream)
+        internal RarArchive(IEnumerable<Stream> streams, ReaderOptions options)
+            : base(ArchiveType.Rar, streams, options)
         {
         }
 
@@ -33,20 +46,9 @@ namespace SharpCompress.Archives.Rar
             return RarArchiveEntryFactory.GetEntries(this, volumes, ReaderOptions);
         }
 
-        protected override IEnumerable<RarVolume> LoadVolumes(SourceStream srcStream)
+        protected override IEnumerable<RarVolume> LoadVolumes(IEnumerable<Stream> streams)
         {
-            base.SrcStream.LoadAllParts(); //request all streams
-            Stream[] streams = base.SrcStream.Streams.ToArray();
-            if (streams.Length > 1 && IsRarFile(streams[1], ReaderOptions)) //test part 2 - true = multipart not split
-            {
-                base.SrcStream.IsVolumes = true;
-                streams[1].Position = 0;
-                base.SrcStream.Position = 0;
-
-                return srcStream.Streams.Select(a => new StreamRarArchiveVolume(a, ReaderOptions));
-            }
-            else //split mode or single file
-                return new StreamRarArchiveVolume(base.SrcStream, ReaderOptions).AsEnumerable();
+            return RarArchiveVolumeFactory.GetParts(streams, ReaderOptions);
         }
 
         protected override IReader CreateReaderForSolidExtraction()
@@ -67,8 +69,7 @@ namespace SharpCompress.Archives.Rar
         public static RarArchive Open(string filePath, ReaderOptions? options = null)
         {
             filePath.CheckNotNullOrEmpty(nameof(filePath));
-            FileInfo fileInfo = new FileInfo(filePath);
-            return new RarArchive(new SourceStream(fileInfo, i => RarArchiveVolumeFactory.GetFilePart(i, fileInfo), options ?? new ReaderOptions()));
+            return new RarArchive(new FileInfo(filePath), options ?? new ReaderOptions());
         }
 
         /// <summary>
@@ -79,7 +80,7 @@ namespace SharpCompress.Archives.Rar
         public static RarArchive Open(FileInfo fileInfo, ReaderOptions? options = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            return new RarArchive(new SourceStream(fileInfo, i => RarArchiveVolumeFactory.GetFilePart(i, fileInfo), options ?? new ReaderOptions()));
+            return new RarArchive(fileInfo, options ?? new ReaderOptions());
         }
 
         /// <summary>
@@ -90,34 +91,20 @@ namespace SharpCompress.Archives.Rar
         public static RarArchive Open(Stream stream, ReaderOptions? options = null)
         {
             stream.CheckNotNull(nameof(stream));
-            return new RarArchive(new SourceStream(stream, i => null, options ?? new ReaderOptions()));
+            return Open(stream.AsEnumerable(), options ?? new ReaderOptions());
         }
 
         /// <summary>
-        /// Constructor with all file parts passed in
-        /// </summary>
-        /// <param name="fileInfos"></param>
-        /// <param name="readerOptions"></param>
-        public static RarArchive Open(IEnumerable<FileInfo> fileInfos, ReaderOptions? readerOptions = null)
-        {
-            fileInfos.CheckNotNull(nameof(fileInfos));
-            FileInfo[] files = fileInfos.ToArray();
-            return new RarArchive(new SourceStream(files[0], i => i < files.Length ? files[i] : null, readerOptions ?? new ReaderOptions()));
-        }
-
-        /// <summary>
-        /// Constructor with all stream parts passed in
+        /// Takes multiple seekable Streams for a multi-part archive
         /// </summary>
         /// <param name="streams"></param>
-        /// <param name="readerOptions"></param>
-        public static RarArchive Open(IEnumerable<Stream> streams, ReaderOptions? readerOptions = null)
+        /// <param name="options"></param>
+        public static RarArchive Open(IEnumerable<Stream> streams, ReaderOptions? options = null)
         {
             streams.CheckNotNull(nameof(streams));
-            Stream[] strms = streams.ToArray();
-            return new RarArchive(new SourceStream(strms[0], i => i < strms.Length ? strms[i] : null, readerOptions ?? new ReaderOptions()));
+            return new RarArchive(streams, options ?? new ReaderOptions());
         }
 
-
         public static bool IsRarFile(string filePath)
         {
             return IsRarFile(new FileInfo(filePath));

src/SharpCompress/Archives/Rar/RarArchiveEntry.cs

@@ -21,7 +21,6 @@ namespace SharpCompress.Archives.Rar
             this.parts = parts.ToList();
             this.archive = archive;
             this.readerOptions = readerOptions;
-            this.IsSolid = this.FileHeader.IsSolid;
         }
 
         public override CompressionType CompressionType => CompressionType.Rar;

src/SharpCompress/Archives/Rar/RarArchiveVolumeFactory.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using SharpCompress.Common.Rar;
@@ -6,35 +6,135 @@ using SharpCompress.Readers;
 using System.Linq;
 using System.Text;
 using SharpCompress.Common.Rar.Headers;
-using System.Text.RegularExpressions;
 
 namespace SharpCompress.Archives.Rar
 {
     internal static class RarArchiveVolumeFactory
     {
-        internal static FileInfo? GetFilePart(int index, FileInfo part1) //base the name on the first part
+        internal static IEnumerable<RarVolume> GetParts(IEnumerable<Stream> streams, ReaderOptions options)
         {
-            FileInfo? item = null;
-
-            //new style rar - ..part1 | /part01 | part001 ....
-            Match m = Regex.Match(part1.Name, @"^(.*\.part)([0-9]+)(\.rar)$", RegexOptions.IgnoreCase);
-            if (m.Success)
-                item = new FileInfo(Path.Combine(part1.DirectoryName!, String.Concat(m.Groups[1].Value, (index + 1).ToString().PadLeft(m.Groups[2].Value.Length, '0'), m.Groups[3].Value)));
-            else
+            foreach (Stream s in streams)
             {
-                //old style - ...rar, .r00, .r01 ...
-                m = Regex.Match(part1.Name, @"^(.*\.r)(ar|[0-9]+)$", RegexOptions.IgnoreCase);
-                if (m.Success)
-                    item = new FileInfo(Path.Combine(part1.DirectoryName!, String.Concat(m.Groups[1].Value, index == 0 ? "ar" : (index - 1).ToString().PadLeft(m.Groups[2].Value.Length, '0'))));
-                else //split .001, .002 ....
-                    return ArchiveVolumeFactory.GetFilePart(index, part1);
+                if (!s.CanRead || !s.CanSeek)
+                {
+                    throw new ArgumentException("Stream is not readable and seekable");
+                }
+                StreamRarArchiveVolume part = new StreamRarArchiveVolume(s, options);
+                yield return part;
             }
-
-            if (item != null && item.Exists)
-                return item;
-
-            return null; //no more items
         }
 
+        internal static IEnumerable<RarVolume> GetParts(FileInfo fileInfo, ReaderOptions options)
+        {
+            FileInfoRarArchiveVolume part = new FileInfoRarArchiveVolume(fileInfo, options);
+            yield return part;
+
+            ArchiveHeader ah = part.ArchiveHeader;
+            if (!ah.IsVolume)
+            {
+                yield break; //if file isn't volume then there is no reason to look
+            }
+            fileInfo = GetNextFileInfo(ah, part.FileParts.FirstOrDefault() as FileInfoRarFilePart)!;
+            //we use fileinfo because rar is dumb and looks at file names rather than archive info for another volume
+            while (fileInfo != null && fileInfo.Exists)
+            {
+                part = new FileInfoRarArchiveVolume(fileInfo, options);
+
+                fileInfo = GetNextFileInfo(ah, part.FileParts.FirstOrDefault() as FileInfoRarFilePart)!;
+                yield return part;
+            }
+        }
+
+        private static FileInfo? GetNextFileInfo(ArchiveHeader ah, FileInfoRarFilePart? currentFilePart)
+        {
+            if (currentFilePart is null)
+            {
+                return null;
+            }
+            bool oldNumbering = ah.OldNumberingFormat
+                                || currentFilePart.MarkHeader.OldNumberingFormat;
+            if (oldNumbering)
+            {
+                return FindNextFileWithOldNumbering(currentFilePart.FileInfo);
+            }
+            else
+            {
+                return FindNextFileWithNewNumbering(currentFilePart.FileInfo);
+            }
+        }
+
+        private static FileInfo FindNextFileWithOldNumbering(FileInfo currentFileInfo)
+        {
+            // .rar, .r00, .r01, ...
+            string extension = currentFileInfo.Extension;
+
+            var buffer = new StringBuilder(currentFileInfo.FullName.Length);
+            buffer.Append(currentFileInfo.FullName.Substring(0,
+                                                             currentFileInfo.FullName.Length - extension.Length));
+            if (string.Compare(extension, ".rar", StringComparison.OrdinalIgnoreCase) == 0)
+            {
+                buffer.Append(".r00");
+            }
+            else
+            {
+                if (int.TryParse(extension.Substring(2, 2), out int num))
+                {
+                    num++;
+                    buffer.Append(".r");
+                    if (num < 10)
+                    {
+                        buffer.Append('0');
+                    }
+                    buffer.Append(num);
+                }
+                else
+                {
+                    ThrowInvalidFileName(currentFileInfo);
+                }
+            }
+            return new FileInfo(buffer.ToString());
+        }
+
+        private static FileInfo FindNextFileWithNewNumbering(FileInfo currentFileInfo)
+        {
+            // part1.rar, part2.rar, ...
+            string extension = currentFileInfo.Extension;
+            if (string.Compare(extension, ".rar", StringComparison.OrdinalIgnoreCase) != 0)
+            {
+                throw new ArgumentException("Invalid extension, expected 'rar': " + currentFileInfo.FullName);
+            }
+            int startIndex = currentFileInfo.FullName.LastIndexOf(".part");
+            if (startIndex < 0)
+            {
+                ThrowInvalidFileName(currentFileInfo);
+            }
+            StringBuilder buffer = new StringBuilder(currentFileInfo.FullName.Length);
+            buffer.Append(currentFileInfo.FullName, 0, startIndex);
+            string numString = currentFileInfo.FullName.Substring(startIndex + 5,
+                                                                  currentFileInfo.FullName.IndexOf('.', startIndex + 5) -
+                                                                  startIndex - 5);
+            buffer.Append(".part");
+            if (int.TryParse(numString, out int num))
+            {
+                num++;
+                for (int i = 0; i < numString.Length - num.ToString().Length; i++)
+                {
+                    buffer.Append('0');
+                }
+                buffer.Append(num);
+            }
+            else
+            {
+                ThrowInvalidFileName(currentFileInfo);
+            }
+            buffer.Append(".rar");
+            return new FileInfo(buffer.ToString());
+        }
+
+        private static void ThrowInvalidFileName(FileInfo fileInfo)
+        {
+            throw new ArgumentException("Filename invalid or next archive could not be found:"
+                                        + fileInfo.FullName);
+        }
     }
-}
+}

src/SharpCompress/Archives/SevenZip/SevenZipArchive.cs

@@ -1,4 +1,4 @@
-#nullable disable
+#nullable disable
 
 using System;
 using System.Collections.Generic;
@@ -34,33 +34,8 @@ namespace SharpCompress.Archives.SevenZip
         public static SevenZipArchive Open(FileInfo fileInfo, ReaderOptions readerOptions = null)
         {
             fileInfo.CheckNotNull("fileInfo");
-            return new SevenZipArchive(new SourceStream(fileInfo, i => ArchiveVolumeFactory.GetFilePart(i, fileInfo), readerOptions ?? new ReaderOptions()));
+            return new SevenZipArchive(fileInfo, readerOptions ?? new ReaderOptions());
         }
-
-        /// <summary>
-        /// Constructor with all file parts passed in
-        /// </summary>
-        /// <param name="fileInfos"></param>
-        /// <param name="readerOptions"></param>
-        public static SevenZipArchive Open(IEnumerable<FileInfo> fileInfos, ReaderOptions readerOptions = null)
-        {
-            fileInfos.CheckNotNull(nameof(fileInfos));
-            FileInfo[] files = fileInfos.ToArray();
-            return new SevenZipArchive(new SourceStream(files[0], i => i < files.Length ? files[i] : null, readerOptions ?? new ReaderOptions()));
-        }
-
-        /// <summary>
-        /// Constructor with all stream parts passed in
-        /// </summary>
-        /// <param name="streams"></param>
-        /// <param name="readerOptions"></param>
-        public static SevenZipArchive Open(IEnumerable<Stream> streams, ReaderOptions readerOptions = null)
-        {
-            streams.CheckNotNull(nameof(streams));
-            Stream[] strms = streams.ToArray();
-            return new SevenZipArchive(new SourceStream(strms[0], i => i < strms.Length ? strms[i] : null, readerOptions ?? new ReaderOptions()));
-        }
-
         /// <summary>
         /// Takes a seekable Stream as a source
         /// </summary>
@@ -69,23 +44,17 @@ namespace SharpCompress.Archives.SevenZip
         public static SevenZipArchive Open(Stream stream, ReaderOptions readerOptions = null)
         {
             stream.CheckNotNull("stream");
-            return new SevenZipArchive(new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions()));
+            return new SevenZipArchive(stream, readerOptions ?? new ReaderOptions());
         }
 
-        /// <summary>
-        /// Constructor with a SourceStream able to handle FileInfo and Streams.
-        /// </summary>
-        /// <param name="srcStream"></param>
-        /// <param name="options"></param>
-        internal SevenZipArchive(SourceStream srcStream)
-            : base(ArchiveType.SevenZip, srcStream)
+        internal SevenZipArchive(FileInfo fileInfo, ReaderOptions readerOptions)
+            : base(ArchiveType.SevenZip, fileInfo, readerOptions)
         {
         }
 
-        protected override IEnumerable<SevenZipVolume> LoadVolumes(SourceStream srcStream)
+        protected override IEnumerable<SevenZipVolume> LoadVolumes(FileInfo file)
         {
-            base.SrcStream.LoadAllParts(); //request all streams
-            return new SevenZipVolume(srcStream, ReaderOptions).AsEnumerable(); //simple single volume or split, multivolume not supported
+            return new SevenZipVolume(file.OpenRead(), ReaderOptions).AsEnumerable();
         }
 
         public static bool IsSevenZipFile(string filePath)
@@ -105,32 +74,38 @@ namespace SharpCompress.Archives.SevenZip
             }
         }
 
+        internal SevenZipArchive(Stream stream, ReaderOptions readerOptions)
+            : base(ArchiveType.SevenZip, stream.AsEnumerable(), readerOptions)
+        {
+        }
+
         internal SevenZipArchive()
             : base(ArchiveType.SevenZip)
         {
         }
 
+        protected override IEnumerable<SevenZipVolume> LoadVolumes(IEnumerable<Stream> streams)
+        {
+            foreach (Stream s in streams)
+            {
+                if (!s.CanRead || !s.CanSeek)
+                {
+                    throw new ArgumentException("Stream is not readable and seekable");
+                }
+                SevenZipVolume volume = new SevenZipVolume(s, ReaderOptions);
+                yield return volume;
+            }
+        }
+
         protected override IEnumerable<SevenZipArchiveEntry> LoadEntries(IEnumerable<SevenZipVolume> volumes)
         {
             var stream = volumes.Single().Stream;
             LoadFactory(stream);
-            var entries = new SevenZipArchiveEntry[database._files.Count];
             for (int i = 0; i < database._files.Count; i++)
             {
                 var file = database._files[i];
-                entries[i] = new SevenZipArchiveEntry(this, new SevenZipFilePart(stream, database, i, file, ReaderOptions.ArchiveEncoding));
+                yield return new SevenZipArchiveEntry(this, new SevenZipFilePart(stream, database, i, file, ReaderOptions.ArchiveEncoding));
             }
-            foreach (var group in entries.Where(x => !x.IsDirectory).GroupBy(x => x.FilePart.Folder))
-            {
-                var isSolid = false;
-                foreach (var entry in group)
-                {
-                    entry.IsSolid = isSolid;
-                    isSolid = true; //mark others in this group as solid - same as rar behaviour.
-                }
-            }
-
-            return entries;
         }
 
         private void LoadFactory(Stream stream)

src/SharpCompress/Archives/Tar/TarArchive.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -34,31 +34,7 @@ namespace SharpCompress.Archives.Tar
         public static TarArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            return new TarArchive(new SourceStream(fileInfo, i => ArchiveVolumeFactory.GetFilePart(i, fileInfo), readerOptions ?? new ReaderOptions()));
-        }
-
-        /// <summary>
-        /// Constructor with all file parts passed in
-        /// </summary>
-        /// <param name="fileInfos"></param>
-        /// <param name="readerOptions"></param>
-        public static TarArchive Open(IEnumerable<FileInfo> fileInfos, ReaderOptions? readerOptions = null)
-        {
-            fileInfos.CheckNotNull(nameof(fileInfos));
-            FileInfo[] files = fileInfos.ToArray();
-            return new TarArchive(new SourceStream(files[0], i => i < files.Length ? files[i] : null, readerOptions ?? new ReaderOptions()));
-        }
-
-        /// <summary>
-        /// Constructor with all stream parts passed in
-        /// </summary>
-        /// <param name="streams"></param>
-        /// <param name="readerOptions"></param>
-        public static TarArchive Open(IEnumerable<Stream> streams, ReaderOptions? readerOptions = null)
-        {
-            streams.CheckNotNull(nameof(streams));
-            Stream[] strms = streams.ToArray();
-            return new TarArchive(new SourceStream(strms[0], i => i < strms.Length ? strms[i] : null, readerOptions ?? new ReaderOptions()));
+            return new TarArchive(fileInfo, readerOptions ?? new ReaderOptions());
         }
 
         /// <summary>
@@ -69,7 +45,7 @@ namespace SharpCompress.Archives.Tar
         public static TarArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
-            return new TarArchive(new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions()));
+            return new TarArchive(stream, readerOptions ?? new ReaderOptions());
         }
 
         public static bool IsTarFile(string filePath)
@@ -104,19 +80,28 @@ namespace SharpCompress.Archives.Tar
             return false;
         }
 
-        protected override IEnumerable<TarVolume> LoadVolumes(SourceStream srcStream)
+        /// <summary>
+        /// Constructor with a FileInfo object to an existing file.
+        /// </summary>
+        /// <param name="fileInfo"></param>
+        /// <param name="readerOptions"></param>
+        internal TarArchive(FileInfo fileInfo, ReaderOptions readerOptions)
+            : base(ArchiveType.Tar, fileInfo, readerOptions)
         {
-            base.SrcStream.LoadAllParts(); //request all streams
-            return new TarVolume(srcStream, ReaderOptions).AsEnumerable(); //simple single volume or split, multivolume not supported
+        }
+
+        protected override IEnumerable<TarVolume> LoadVolumes(FileInfo file)
+        {
+            return new TarVolume(file.OpenRead(), ReaderOptions).AsEnumerable();
         }
 
         /// <summary>
-        /// Constructor with a SourceStream able to handle FileInfo and Streams.
+        /// Takes multiple seekable Streams for a multi-part archive
         /// </summary>
-        /// <param name="srcStream"></param>
-        /// <param name="options"></param>
-        internal TarArchive(SourceStream srcStream)
-            : base(ArchiveType.Tar, srcStream)
+        /// <param name="stream"></param>
+        /// <param name="readerOptions"></param>
+        internal TarArchive(Stream stream, ReaderOptions readerOptions)
+            : base(ArchiveType.Tar, stream, readerOptions)
         {
         }
 
@@ -125,6 +110,11 @@ namespace SharpCompress.Archives.Tar
         {
         }
 
+        protected override IEnumerable<TarVolume> LoadVolumes(IEnumerable<Stream> streams)
+        {
+            return new TarVolume(streams.First(), ReaderOptions).AsEnumerable();
+        }
+
         protected override IEnumerable<TarArchiveEntry> LoadEntries(IEnumerable<TarVolume> volumes)
         {
             Stream stream = volumes.Single().Stream;

src/SharpCompress/Archives/Zip/ZipArchive.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -6,7 +6,6 @@ using SharpCompress.Common;
 using SharpCompress.Common.Zip;
 using SharpCompress.Common.Zip.Headers;
 using SharpCompress.Compressors.Deflate;
-using SharpCompress.IO;
 using SharpCompress.Readers;
 using SharpCompress.Readers.Zip;
 using SharpCompress.Writers;
@@ -26,17 +25,6 @@ namespace SharpCompress.Archives.Zip
         /// </summary>
         public CompressionLevel DeflateCompressionLevel { get; set; }
 
-        /// <summary>
-        /// Constructor with a SourceStream able to handle FileInfo and Streams.
-        /// </summary>
-        /// <param name="srcStream"></param>
-        /// <param name="options"></param>
-        internal ZipArchive(SourceStream srcStream)
-            : base(ArchiveType.Zip, srcStream)
-        {
-            headerFactory = new SeekableZipHeaderFactory(srcStream.ReaderOptions.Password, srcStream.ReaderOptions.ArchiveEncoding);
-        }
-
         /// <summary>
         /// Constructor expects a filepath to an existing file.
         /// </summary>
@@ -56,31 +44,7 @@ namespace SharpCompress.Archives.Zip
         public static ZipArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            return new ZipArchive(new SourceStream(fileInfo, i => ZipArchiveVolumeFactory.GetFilePart(i, fileInfo), readerOptions ?? new ReaderOptions()));
-        }
-
-        /// <summary>
-        /// Constructor with all file parts passed in
-        /// </summary>
-        /// <param name="fileInfos"></param>
-        /// <param name="readerOptions"></param>
-        public static ZipArchive Open(IEnumerable<FileInfo> fileInfos, ReaderOptions? readerOptions = null)
-        {
-            fileInfos.CheckNotNull(nameof(fileInfos));
-            FileInfo[] files = fileInfos.ToArray();
-            return new ZipArchive(new SourceStream(files[0], i => i < files.Length ? files[i] : null, readerOptions ?? new ReaderOptions()));
-        }
-
-        /// <summary>
-        /// Constructor with all stream parts passed in
-        /// </summary>
-        /// <param name="streams"></param>
-        /// <param name="readerOptions"></param>
-        public static ZipArchive Open(IEnumerable<Stream> streams, ReaderOptions? readerOptions = null)
-        {
-            streams.CheckNotNull(nameof(streams));
-            Stream[] strms = streams.ToArray();
-            return new ZipArchive(new SourceStream(strms[0], i => i < strms.Length ? strms[i] : null, readerOptions ?? new ReaderOptions()));
+            return new ZipArchive(fileInfo, readerOptions ?? new ReaderOptions());
         }
 
         /// <summary>
@@ -91,7 +55,7 @@ namespace SharpCompress.Archives.Zip
         public static ZipArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
-            return new ZipArchive(new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions()));
+            return new ZipArchive(stream, readerOptions ?? new ReaderOptions());
         }
 
         public static bool IsZipFile(string filePath, string? password = null)
@@ -133,61 +97,20 @@ namespace SharpCompress.Archives.Zip
             }
         }
 
-        public static bool IsZipMulti(Stream stream, string? password = null)
+        /// <summary>
+        /// Constructor with a FileInfo object to an existing file.
+        /// </summary>
+        /// <param name="fileInfo"></param>
+        /// <param name="readerOptions"></param>
+        internal ZipArchive(FileInfo fileInfo, ReaderOptions readerOptions)
+            : base(ArchiveType.Zip, fileInfo, readerOptions)
         {
-            StreamingZipHeaderFactory headerFactory = new StreamingZipHeaderFactory(password, new ArchiveEncoding());
-            try
-            {
-                ZipHeader? header = headerFactory.ReadStreamHeader(stream).FirstOrDefault(x => x.ZipHeaderType != ZipHeaderType.Split);
-                if (header is null)
-                {
-                    if (stream.CanSeek) //could be multipart. Test for central directory - might not be z64 safe
-                    {
-                        SeekableZipHeaderFactory z = new SeekableZipHeaderFactory(password, new ArchiveEncoding());
-                        var x = z.ReadSeekableHeader(stream).FirstOrDefault();
-                        return x?.ZipHeaderType == ZipHeaderType.DirectoryEntry;
-                    }
-                    else
-                        return false;
-                }
-                return Enum.IsDefined(typeof(ZipHeaderType), header.ZipHeaderType);
-            }
-            catch (CryptographicException)
-            {
-                return true;
-            }
-            catch
-            {
-                return false;
-            }
+            headerFactory = new SeekableZipHeaderFactory(readerOptions.Password, readerOptions.ArchiveEncoding);
         }
 
-        protected override IEnumerable<ZipVolume> LoadVolumes(SourceStream srcStream)
+        protected override IEnumerable<ZipVolume> LoadVolumes(FileInfo file)
         {
-            base.SrcStream.LoadAllParts(); //request all streams
-            base.SrcStream.Position = 0;
-
-            List<Stream> streams = base.SrcStream.Streams.ToList();
-            if (streams.Count > 1) //test part 2 - true = multipart not split
-            {
-                streams[1].Position += 4; //skip the POST_DATA_DESCRIPTOR to prevent an exception
-                bool isZip = IsZipFile(streams[1], ReaderOptions.Password);
-                streams[1].Position -= 4;
-                if (isZip)
-                {
-                    base.SrcStream.IsVolumes = true;
-
-                    var tmp = streams[0]; //arcs as zip, z01 ... swap the zip the end
-                    streams.RemoveAt(0);
-                    streams.Add(tmp);
-
-                    //streams[0].Position = 4; //skip the POST_DATA_DESCRIPTOR to prevent an exception
-                    return streams.Select(a => new ZipVolume(a, ReaderOptions));
-                }
-            }
-
-            //split mode or single file
-            return new ZipVolume(base.SrcStream, ReaderOptions).AsEnumerable();
+            return new ZipVolume(file.OpenRead(), ReaderOptions).AsEnumerable();
         }
 
         internal ZipArchive()
@@ -195,35 +118,46 @@ namespace SharpCompress.Archives.Zip
         {
         }
 
+        /// <summary>
+        /// Takes multiple seekable Streams for a multi-part archive
+        /// </summary>
+        /// <param name="stream"></param>
+        /// <param name="readerOptions"></param>
+        internal ZipArchive(Stream stream, ReaderOptions readerOptions)
+            : base(ArchiveType.Zip, stream, readerOptions)
+        {
+            headerFactory = new SeekableZipHeaderFactory(readerOptions.Password, readerOptions.ArchiveEncoding);
+        }
+
+        protected override IEnumerable<ZipVolume> LoadVolumes(IEnumerable<Stream> streams)
+        {
+            return new ZipVolume(streams.First(), ReaderOptions).AsEnumerable();
+        }
+
         protected override IEnumerable<ZipArchiveEntry> LoadEntries(IEnumerable<ZipVolume> volumes)
         {
-            var vols = volumes.ToArray();
-            foreach (ZipHeader h in headerFactory.ReadSeekableHeader(vols.Last().Stream))
+            var volume = volumes.Single();
+            Stream stream = volume.Stream;
+            foreach (ZipHeader h in headerFactory.ReadSeekableHeader(stream))
             {
                 if (h != null)
                 {
                     switch (h.ZipHeaderType)
                     {
                         case ZipHeaderType.DirectoryEntry:
-                        {
-                            DirectoryEntryHeader deh = (DirectoryEntryHeader)h;
-                            Stream s;
-                            if (deh.RelativeOffsetOfEntryHeader + deh.CompressedSize > vols[deh.DiskNumberStart].Stream.Length)
                             {
-                                var v = vols.Skip(deh.DiskNumberStart).ToArray();
-                                s = new SourceStream(v[0].Stream, i => i < v.Length ? v[i].Stream : null, new ReaderOptions() { LeaveStreamOpen = true });
+                                yield return new ZipArchiveEntry(this,
+                                                                 new SeekableZipFilePart(headerFactory,
+                                                                                         (DirectoryEntryHeader)h,
+                                                                                         stream));
                             }
-                            else
-                                s = vols[deh.DiskNumberStart].Stream;
-                            yield return new ZipArchiveEntry(this, new SeekableZipFilePart(headerFactory, deh, s));
-                        }
-                        break;
+                            break;
                         case ZipHeaderType.DirectoryEnd:
-                        {
-                            byte[] bytes = ((DirectoryEndHeader)h).Comment ?? Array.Empty<byte>();
-                            volumes.Last().Comment = ReaderOptions.ArchiveEncoding.Decode(bytes);
-                            yield break;
-                        }
+                            {
+                                byte[] bytes = ((DirectoryEndHeader)h).Comment ?? Array.Empty<byte>();
+                                volume.Comment = ReaderOptions.ArchiveEncoding.Decode(bytes);
+                                yield break;
+                            }
                     }
                 }
             }

src/SharpCompress/Archives/Zip/ZipArchiveVolumeFactory.cs

@@ -1,34 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.IO;
-using SharpCompress.Common.Rar;
-using SharpCompress.Readers;
-using System.Linq;
-using System.Text;
-using SharpCompress.Common.Rar.Headers;
-using System.Text.RegularExpressions;
-
-namespace SharpCompress.Archives.Zip
-{
-    internal static class ZipArchiveVolumeFactory
-    {
-        internal static FileInfo? GetFilePart(int index, FileInfo part1) //base the name on the first part
-        {
-            FileInfo? item = null;
-
-            //load files with zip/zipx first. Swapped to end once loaded in ZipArchive
-            //new style .zip, z01.. | .zipx, zx01 - if the numbers go beyond 99 then they use 100 ...1000 etc
-            Match m = Regex.Match(part1.Name, @"^(.*\.)(zipx?|zx?[0-9]+)$", RegexOptions.IgnoreCase);
-            if (m.Success)
-                item = new FileInfo(Path.Combine(part1.DirectoryName!, String.Concat(m.Groups[1].Value, Regex.Replace(m.Groups[2].Value, @"[^xz]", ""), index.ToString().PadLeft(2, '0'))));
-            else //split - 001, 002 ...
-                return ArchiveVolumeFactory.GetFilePart(index, part1);
-
-            if (item != null && item.Exists)
-                return item;
-
-            return null; //no more items
-        }
-
-    }
-}

src/SharpCompress/AssemblyInfo.cs

@@ -5,7 +5,7 @@ using System.Runtime.CompilerServices;
 [assembly: AssemblyTitle("SharpCompress")]
 [assembly: AssemblyProduct("SharpCompress")]
 [assembly: InternalsVisibleTo("SharpCompress.Test" + SharpCompress.AssemblyInfo.PublicKeySuffix)]
-[assembly: CLSCompliant(true)]
+[assembly: CLSCompliant(false)]
 
 namespace SharpCompress
 {

src/SharpCompress/Common/ArchiveType.cs

@@ -6,6 +6,7 @@
         Zip,
         Tar,
         SevenZip,
-        GZip
+        GZip,
+        ZStandard
     }
 }

src/SharpCompress/Common/CompressionType.cs

@@ -14,6 +14,7 @@
         LZip,
         Xz,
         Unknown,
-        Deflate64
+        Deflate64,
+        ZStandard,
     }
 }

src/SharpCompress/Common/Entry.cs

@@ -75,7 +75,7 @@ namespace SharpCompress.Common
 
         internal abstract IEnumerable<FilePart> Parts { get; }
 
-        public bool IsSolid { get; set; }
+        internal bool IsSolid { get; set; }
 
         internal virtual void Close()
         {

src/SharpCompress/Common/IEntry.cs

@@ -14,7 +14,6 @@ namespace SharpCompress.Common
         bool IsDirectory { get; }
         bool IsEncrypted { get; }
         bool IsSplitAfter { get; }
-        bool IsSolid { get; }
         DateTime? LastAccessedTime { get; }
         DateTime? LastModifiedTime { get; }
         long Size { get; }

src/SharpCompress/Common/Rar/RarEntry.cs

@@ -10,7 +10,7 @@ namespace SharpCompress.Common.Rar
         /// <summary>
         /// As the V2017 port isn't complete, add this check to use the legacy Rar code.
         /// </summary>
-        internal bool IsRarV3 => FileHeader.CompressionAlgorithm == 20 || FileHeader.CompressionAlgorithm == 26 || FileHeader.CompressionAlgorithm == 29 || FileHeader.CompressionAlgorithm == 36; //Nanook - Added 20+26 as Test arc from WinRar2.8 (algo 20) was failing with 2017 code
+        internal bool IsRarV3 => FileHeader.CompressionAlgorithm == 29 || FileHeader.CompressionAlgorithm == 36;
 
         /// <summary>
         /// The File's 32 bit CRC Hash

src/SharpCompress/Common/SevenZip/ArchiveReader.cs

@@ -1248,7 +1248,7 @@ namespace SharpCompress.Common.SevenZip
 
             if (nextHeaderOffset > _streamEnding - db._startPositionAfterHeader)
             {
-                throw new InvalidOperationException("nextHeaderOffset is invalid");
+                throw new IndexOutOfRangeException();
             }
 
             _stream.Seek(nextHeaderOffset, SeekOrigin.Current);

src/SharpCompress/Common/SevenZip/CFolder.cs

@@ -30,7 +30,7 @@ namespace SharpCompress.Common.SevenZip
                 }
             }
 
-            throw new InvalidOperationException();
+            throw new Exception();
         }
 
         public int GetNumOutStreams()
@@ -185,4 +185,4 @@ namespace SharpCompress.Common.SevenZip
             return true;
         }
     }
-}
+}

src/SharpCompress/Common/Tar/Headers/TarHeader.cs

@@ -19,9 +19,11 @@ namespace SharpCompress.Common.Tar.Headers
         internal string Name { get; set; }
         internal string LinkName { get; set; }
 
-        internal long Mode { get; set; }
-        internal long UserId { get; set; }
-        internal long GroupId { get; set; }
+        //internal int Mode { get; set; }
+        //internal int UserId { get; set; }
+        //internal string UserName { get; set; }
+        //internal int GroupId { get; set; }
+        //internal string GroupName { get; set; }
         internal long Size { get; set; }
         internal DateTime LastModifiedTime { get; set; }
         internal EntryType EntryType { get; set; }
@@ -125,12 +127,9 @@ namespace SharpCompress.Common.Tar.Headers
             EntryType = ReadEntryType(buffer);
             Size = ReadSize(buffer);
 
-            Mode = ReadAsciiInt64Base8(buffer, 100, 7);
-            if(EntryType == EntryType.Directory) 
-                Mode |= 0b1_000_000_000;
-
-            UserId = ReadAsciiInt64Base8(buffer, 108, 7);
-            GroupId = ReadAsciiInt64Base8(buffer, 116, 7);
+            //Mode = ReadASCIIInt32Base8(buffer, 100, 7);
+            //UserId = ReadASCIIInt32Base8(buffer, 108, 7);
+            //GroupId = ReadASCIIInt32Base8(buffer, 116, 7);
             long unixTimeStamp = ReadAsciiInt64Base8(buffer, 136, 11);
             LastModifiedTime = EPOCH.AddSeconds(unixTimeStamp).ToLocalTime();
 

src/SharpCompress/Common/Tar/TarEntry.cs

@@ -44,12 +44,6 @@ namespace SharpCompress.Common.Tar
 
         public override bool IsSplitAfter => false;
 
-        public long Mode => _filePart.Header.Mode;
-
-        public long UserID => _filePart.Header.UserId;
-        
-        public long GroupId => _filePart.Header.GroupId;
-
         internal override IEnumerable<FilePart> Parts => _filePart.AsEnumerable<FilePart>();
 
         internal static IEnumerable<TarEntry> GetEntries(StreamingMode mode, Stream stream,

src/SharpCompress/Common/ZStandard/ZStandardEntry.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using SharpCompress.Common.GZip;
+
+namespace SharpCompress.Common.ZStandard
+{
+    public class ZStandardEntry : Entry
+    {
+        private readonly ZStandardFilePart _filePart;
+
+        internal ZStandardEntry(ZStandardFilePart filePart)
+        {
+            _filePart = filePart;
+        }
+
+        public override CompressionType CompressionType => CompressionType.GZip;
+
+        public override long Crc => _filePart.Crc ?? 0;
+
+        public override string Key => _filePart.FilePartName;
+
+        public override string? LinkTarget => null;
+
+        public override long CompressedSize => 0;
+
+        public override long Size => _filePart.UncompressedSize ?? 0;
+
+        public override DateTime? LastModifiedTime => _filePart.DateModified;
+
+        public override DateTime? CreatedTime => null;
+
+        public override DateTime? LastAccessedTime => null;
+
+        public override DateTime? ArchivedTime => null;
+
+        public override bool IsEncrypted => false;
+
+        public override bool IsDirectory => false;
+
+        public override bool IsSplitAfter => false;
+
+        internal override IEnumerable<FilePart> Parts => _filePart.AsEnumerable<FilePart>();
+
+        internal static IEnumerable<GZipEntry> GetEntries(Stream stream, OptionsBase options)
+        {
+            yield return new GZipEntry(new GZipFilePart(stream, options.ArchiveEncoding));
+        }
+    }
+}

src/SharpCompress/Common/ZStandard/ZStandardFilePart.cs

@@ -0,0 +1,37 @@
+using System;
+using System.IO;
+using ZstdSharp;
+
+namespace SharpCompress.Common.ZStandard
+{
+    internal sealed class ZStandardFilePart : FilePart
+    {
+        private string _name = "";
+        private readonly Stream _stream;
+
+        internal ZStandardFilePart(Stream stream, ArchiveEncoding archiveEncoding)
+            : base(archiveEncoding)
+        {
+            _stream = stream;
+            EntryStartPosition = stream.Position;
+        }
+
+        internal long EntryStartPosition { get; }
+
+        internal DateTime? DateModified { get; private set; }
+        internal int? Crc { get; private set; }
+        internal int? UncompressedSize { get; private set; }
+
+        internal override string FilePartName => _name!;
+
+        internal override Stream GetCompressedStream()
+        {
+            return new DecompressionStream(_stream);
+        }
+
+        internal override Stream GetRawStream()
+        {
+            return _stream;
+        }
+    }
+}

src/SharpCompress/Common/ZStandard/ZStandardVolume.cs

@@ -0,0 +1,23 @@
+using System.IO;
+using SharpCompress.Readers;
+
+namespace SharpCompress.Common.ZStandard
+{
+    public class ZStandardVolume : Volume
+    {
+        public ZStandardVolume(Stream stream, ReaderOptions options)
+            : base(stream, options)
+        {
+        }
+
+        public ZStandardVolume(FileInfo fileInfo, ReaderOptions options)
+            : base(fileInfo.OpenRead(), options)
+        {
+            options.LeaveStreamOpen = false;
+        }
+
+        public override bool IsFirstVolume => true;
+
+        public override bool IsMultiVolume => true;
+    }
+}

src/SharpCompress/Common/Zip/ZipFilePart.cs

@@ -174,7 +174,7 @@ namespace SharpCompress.Common.Zip
 
                     default:
                         {
-                            throw new InvalidOperationException("Header.CompressionMethod is invalid");
+                            throw new ArgumentOutOfRangeException();
                         }
 
                 }

src/SharpCompress/Compressors/Deflate/Zlib.cs

@@ -1,20 +1,20 @@
 // Zlib.cs
 // ------------------------------------------------------------------
 //
-// Copyright (c) 2009 Dino Chiesa and Microsoft Corporation.
+// Copyright (c) 2009 Dino Chiesa and Microsoft Corporation.  
 // All rights reserved.
 //
 // This code module is part of DotNetZip, a zipfile class library.
 //
 // ------------------------------------------------------------------
 //
-// This code is licensed under the Microsoft Public License.
+// This code is licensed under the Microsoft Public License. 
 // See the file License.txt for the license details.
 // More info on: http://dotnetzip.codeplex.com
 //
 // ------------------------------------------------------------------
 //
-// last saved (in emacs):
+// last saved (in emacs): 
 // Time-stamp: <2009-November-07 05:26:55>
 //
 // ------------------------------------------------------------------
@@ -27,22 +27,22 @@
 // included below.
 //
 // ------------------------------------------------------------------
-//
+// 
 // Copyright (c) 2000,2001,2002,2003 ymnk, JCraft,Inc. All rights reserved.
-//
+// 
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are met:
-//
+// 
 // 1. Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
-//
-// 2. Redistributions in binary form must reproduce the above copyright
-// notice, this list of conditions and the following disclaimer in
+// 
+// 2. Redistributions in binary form must reproduce the above copyright 
+// notice, this list of conditions and the following disclaimer in 
 // the documentation and/or other materials provided with the distribution.
-//
+// 
 // 3. The names of the authors may not be used to endorse or promote products
 // derived from this software without specific prior written permission.
-//
+// 
 // THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
 // INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 // FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
@@ -53,7 +53,7 @@
 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 // EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
+// 
 // -----------------------------------------------------------------------
 //
 // This program is based on zlib-1.1.3; credit to authors
@@ -82,7 +82,7 @@ namespace SharpCompress.Compressors.Deflate
         /// <summary>
         /// Same as None.
         /// </summary>
-        Level0 = None,
+        Level0 = 0,
 
         /// <summary>
         /// The fastest but least effective compression.
@@ -92,7 +92,7 @@ namespace SharpCompress.Compressors.Deflate
         /// <summary>
         /// A synonym for BestSpeed.
         /// </summary>
-        Level1 = BestSpeed,
+        Level1 = 1,
 
         /// <summary>
         /// A little slower, but better, than level 1.
@@ -115,14 +115,14 @@ namespace SharpCompress.Compressors.Deflate
         Level5 = 5,
 
         /// <summary>
-        /// The default compression level, with a good balance of speed and compression efficiency.
+        /// The default compression level, with a good balance of speed and compression efficiency.   
         /// </summary>
         Default = 6,
 
         /// <summary>
         /// A synonym for Default.
         /// </summary>
-        Level6 = Default,
+        Level6 = 6,
 
         /// <summary>
         /// Pretty good compression!
@@ -135,7 +135,7 @@ namespace SharpCompress.Compressors.Deflate
         Level8 = 8,
 
         /// <summary>
-        /// The "best" compression, where best means greatest reduction in size of the input data stream.
+        /// The "best" compression, where best means greatest reduction in size of the input data stream. 
         /// This is also the slowest compression.
         /// </summary>
         BestCompression = 9,
@@ -143,7 +143,7 @@ namespace SharpCompress.Compressors.Deflate
         /// <summary>
         /// A synonym for BestCompression.
         /// </summary>
-        Level9 = BestCompression
+        Level9 = 9
     }
 
     /// <summary>
@@ -154,7 +154,7 @@ namespace SharpCompress.Compressors.Deflate
     public enum CompressionStrategy
     {
         /// <summary>
-        /// The default strategy is probably the best for normal data.
+        /// The default strategy is probably the best for normal data. 
         /// </summary>
         Default = 0,
 
@@ -181,7 +181,7 @@ namespace SharpCompress.Compressors.Deflate
     {
         /// <summary>
         /// The ZlibException class captures exception information generated
-        /// by the Zlib library.
+        /// by the Zlib library. 
         /// </summary>
         public ZlibException()
         {
@@ -233,7 +233,7 @@ namespace SharpCompress.Compressors.Deflate
         /// <param name="target">Contains the array of characteres read from the source TextReader.</param>
         /// <param name="start">The starting index of the target array.</param>
         /// <param name="count">The maximum number of characters to read from the source TextReader.</param>
-        ///
+        /// 
         /// <returns>
         ///   The number of characters read. The number will be less than or equal to
         ///   count depending on the data available in the source TextReader. Returns -1
@@ -405,4 +405,4 @@ namespace SharpCompress.Compressors.Deflate
             BitLengths = new StaticTree(null, extra_blbits, 0, InternalConstants.BL_CODES, InternalConstants.MAX_BL_BITS);
         }
     }
-}
+}

src/SharpCompress/Compressors/Filters/BranchExecFilter.cs

@@ -1,297 +0,0 @@
-/*
- * BranchExecFilter.cs -- Converters for executable
- * <Contribution by Louis-Michel Bergeron, on behalf of aDolus Technolog Inc., 2022>
- * @TODO Encoding
- */
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace SharpCompress.Compressors.Filters
-{
-    [CLSCompliant(false)]
-    public sealed class BranchExecFilter
-    {
-        public enum Alignment : int
-        {
-            ARCH_x86_ALIGNMENT = 1,
-            ARCH_PowerPC_ALIGNMENT = 4,
-            ARCH_IA64_ALIGNMENT = 16,
-            ARCH_ARM_ALIGNMENT = 4,
-            ARCH_ARMTHUMB_ALIGNMENT = 2,
-            ARCH_SPARC_ALIGNMENT = 4,
-        }
-
-        public static void X86Converter(byte[] data, UInt32 ip, ref UInt32 state) {
-
-            long i = 0;
-            long size = data.Length;
-            UInt32 pos = 0;
-            UInt32 mask = state & 7;
-            if (size < 5)
-                return;
-            size -= 4;
-            ip += 5;
-            
-            for (;;)
-            {
-                i = pos;
-            
-                for (; i < size; i++)
-                {
-                    if ((data[i] & 0xFE) == 0xE8)
-                    {
-                        break;
-                    }
-                }
-
-                UInt32 d = (UInt32)(i) - pos;
-                pos = (UInt32)i;
-                if (i >= size)
-                {
-                    state = (d > 2 ? 0 : mask >> (int)d);
-                    return;
-                }
-                if (d > 2)
-                {
-                    mask = 0;
-                }
-                else
-                {
-                    mask >>= (int)d;
-                    if (mask != 0 && (mask > 4 || mask == 3 || (((((data[(UInt32)(mask >> 1) + 1])) + 1) & 0xFE) == 0) ))
-                    {
-                        mask = (mask >> 1) | 4;
-                        pos++;
-                        continue;
-                    }
-                }
-            
-                if ((((data[i + 4]) + 1) & 0xFE) == 0)
-                {
-                    UInt32 inst = ((UInt32)data[i + 4] << 24) | ((UInt32)data[i + 3] << 16) | ((UInt32)data[i + 2] << 8) | ((UInt32)data[i + 1]);
-                    UInt32 cur = ip + (UInt32)pos;
-                    pos += 5;
-
-                    inst -= cur;
-                    if (mask != 0)
-                    {
-                        UInt32 sh = (mask & 6) << 2;
-                        if (((((((Byte)(inst >> (int)sh))) + 1) & 0xFE) == 0))
-                        {
-                            inst ^= (((UInt32)0x100 << (int)sh) - 1);
-                            inst -= cur;
-                        }
-                        mask = 0;
-                    }
-                    data[i + 1] = (Byte)inst;
-                    data[i + 2] = (Byte)(inst >> 8);
-                    data[i + 3] = (Byte)(inst >> 16);
-                    data[i + 4] = (Byte)(0 - ((inst >> 24) & 1));
-                }
-                else
-                {
-                    mask = (mask >> 1) | 4;
-                    pos++;
-                }
-            }
-        }
-
-        public static void PowerPCConverter(byte[] data, UInt32 ip)
-        {
-            long i = 0;
-            long size = data.Length;
-            size &= ~(UInt32)3;
-            ip -= 4;
-
-            for (;; )          // infinite loop
-            {
-                for (;; )          // infinite loop
-                {
-                    if (i >= size)
-                        return;
-                    i += 4;
-
-                    if ((data[i - 4] & 0xFC) == 0x48 && (data[i - 1] & 3) == 1)
-                        break;
-                }
-                {
-                    UInt32 inst = BitConverter.ToUInt32(data, (int)i - 4);
-
-                    if (BitConverter.IsLittleEndian)
-                    {
-                        inst = Utility.SwapUINT32(inst);
-                    }
-
-                    inst -= (UInt32)(ip + i);
-                    inst &= 0x03FFFFFF;
-                    inst |= 0x48000000;
-
-                    Utility.SetBigUInt32(ref data, inst, (i - 4));
-                }
-            }
-        }
-
-        public static void ARMConverter(byte[] data, UInt32 ip)
-        {
-            long i = 0;
-            long size = data.Length;
-            size &= ~(UInt32)3;
-            ip += 4;
-
-            for (;;)          // infinite loop
-            {
-                for (;;)          // infinite loop
-                {
-                    if (i >= size)
-                    {
-                        return;
-                    }
-
-                    i += 4;
-                    if (data[i - 1] == 0xEB)
-                        break;
-                }
-
-                UInt32 inst = BitConverter.ToUInt32(data, (int)i - 4);
-                inst <<= 2;
-                inst -= (UInt32)(ip + i);
-                inst >>= 2;
-                inst &= 0x00FFFFFF;
-                inst |= 0xEB000000;
-
-                Utility.SetLittleUInt32(ref data, inst, i - 4);
-            }
-        }
-
-        public static void ARMTConverter(byte[] data, UInt32 ip)
-        {
-            long i = 0;
-            long size = data.Length;
-            size &= ~(UInt32)1;
-            long lim = size - 4;
-
-            for (;;)
-            {
-                UInt32 b1;
-                for (;;)
-                {
-                    UInt32 b3;
-                    if (i > lim)
-                        return;
-                    b1 = data[i + 1];
-                    b3 = data[i + 3];
-                    i += 2;
-                    b1 ^= 8;
-                    if ((b3 & b1) >= 0xF8)
-                        break;
-                }
-
-             UInt32 inst = ((UInt32)b1 << 19)
-                        + (((UInt32)data[i + 1] & 0x7) << 8)
-                        + (((UInt32)data[i - 2] << 11))
-                        + (data[i]);
-             
-            i += 2;
-
-            UInt32 cur = ((UInt32)(ip + i)) >> 1;
-            inst -= cur;
-
-            
-            data[i - 4] = (Byte)(inst >> 11);
-            data[i - 3] = (Byte)(0xF0 | ((inst >> 19) & 0x7));
-            data[i - 2] = (Byte)inst;
-            data[i - 1] = (Byte)(0xF8 | (inst >> 8));
-            }
-        }
-
-        public static void IA64Converter(byte[] data, UInt32 ip)
-        {
-            UInt32 i = 0;
-            long size = data.Length;
-            if (size < 16)
-                throw new InvalidDataException("Unexpected data size");
-            size -= 16;
-
-            do
-            {
-                UInt32 m = ((UInt32)0x334B0000 >> (data[i] & 0x1E)) & 3;
-                if (m != 0)
-                {
-                    m++;
-                    do
-                    {
-                        UInt32 iterator = (UInt32)( (i + (m * 5) - 8));
-                        if (((data[iterator + 3] >> (int)m) & 15) == 5
-                            && (((data[iterator - 1] | ((UInt32)data[iterator] << 8)) >> (int)m) & 0x70) == 0)
-                        {
-                            UInt32 raw = BitConverter.ToUInt32(data, (int)iterator);
-                            UInt32 inst = raw >> (int)m;
-                            inst = (inst & 0xFFFFF) | ((inst & (1 << 23)) >> 3);
-
-                            inst <<= 4;
-                            inst -= (ip + (UInt32)i);
-                            inst >>= 4;
-
-                            inst &= 0x1FFFFF;
-                            inst += 0x700000;
-                            inst &= 0x8FFFFF;
-                            raw &= ~((UInt32)0x8FFFFF << (int)m);
-                            raw |= (inst << (int)m);
-
-                            Utility.SetLittleUInt32(ref data, raw, iterator);
-                        }
-                    }
-                    while (++m <= 4);
-                }
-                i += 16;
-            }
-            while (i <= size);
-            return;
-        }
-
-        public static void SPARCConverter(byte[] data, UInt32 ip)
-        {
-            long i = 0;
-            long size = data.Length;
-            size &= ~(UInt32)3;
-            ip -= 4;
-
-            for (;;)          // infinite loop
-            {
-                for (;;)          // infinite loop
-                {
-                    if (i >= size)
-                        return;
-
-                    i += 4;
-                    if ((data[i - 4] == 0x40 && (data[i - 3] & 0xC0) == 0) ||
-                        (data[i - 4] == 0x7F && (data[i - 3] >= 0xC0)))
-                        break;
-                }
-                
-                UInt32 inst = BitConverter.ToUInt32(data, (int)i - 4);
-
-                if (BitConverter.IsLittleEndian)
-                {
-                    inst = Utility.SwapUINT32(inst);
-                }
-
-                inst <<= 2;
-                inst -= (UInt32)(ip + i);
-
-                inst &= 0x01FFFFFF;
-                inst -= (UInt32)1 << 24;
-                inst ^= 0xFF000000;
-                inst >>= 2;
-                inst |= 0x40000000;
-
-                Utility.SetBigUInt32(ref data, inst, (i - 4));
-            }
-        }
-    }
-}

src/SharpCompress/Compressors/LZMA/AesDecoderStream.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.IO;
 using System.Security.Cryptography;
 using System.Text;
@@ -20,11 +20,6 @@ namespace SharpCompress.Compressors.LZMA
 
         public AesDecoderStream(Stream input, byte[] info, IPasswordProvider pass, long limit)
         {
-            if (pass.CryptoGetTextPassword() == null)
-            {
-                throw new SharpCompress.Common.CryptographicException("Encrypted 7Zip archive has no password specified.");
-            }
-
             mStream = input;
             mLimit = limit;
 
@@ -148,8 +143,8 @@ namespace SharpCompress.Compressors.LZMA
 
             if ((bt & 0xC0) == 0)
             {
-                salt = Array.Empty<byte>();
-                iv = Array.Empty<byte>();
+                salt = new byte[0];
+                iv = new byte[0];
                 return;
             }
 

src/SharpCompress/Compressors/LZMA/LZ/LzBinTree.cs

@@ -103,7 +103,7 @@ namespace SharpCompress.Compressors.LZMA.LZ
         {
             if (historySize > K_MAX_VAL_FOR_NORMALIZE - 256)
             {
-                throw new ArgumentOutOfRangeException(nameof(historySize));
+                throw new Exception();
             }
             _cutValue = 16 + (matchMaxLen >> 1);
 
@@ -423,4 +423,4 @@ namespace SharpCompress.Compressors.LZMA.LZ
             _cutValue = cutValue;
         }
     }
-}
+}

src/SharpCompress/Compressors/LZMA/LzmaEncoder.cs

@@ -1649,7 +1649,7 @@ namespace SharpCompress.Compressors.LZMA
         {
             for (int m = 0; m < K_MATCH_FINDER_I_DS.Length; m++)
             {
-                if (string.Equals(s, K_MATCH_FINDER_I_DS[m], StringComparison.OrdinalIgnoreCase))
+                if (s == K_MATCH_FINDER_I_DS[m])
                 {
                     return m;
                 }
@@ -1696,7 +1696,7 @@ namespace SharpCompress.Compressors.LZMA
                                 throw new InvalidParamException();
                             }
                             EMatchFinderType matchFinderIndexPrev = _matchFinderType;
-                            int m = FindMatchFinder(((string)prop));
+                            int m = FindMatchFinder(((string)prop).ToUpper());
                             if (m < 0)
                             {
                                 throw new InvalidParamException();

src/SharpCompress/Compressors/LZMA/Utilites/CrcCheckStream.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Diagnostics;
 using System.IO;
 
@@ -21,17 +21,16 @@ namespace SharpCompress.Compressors.LZMA.Utilites
 
         protected override void Dispose(bool disposing)
         {
-            //Nanook - is not equal here - _mCurrentCrc is yet to be negated
-            //if (_mCurrentCrc != _mExpectedCrc)
-            //{
-            //    throw new InvalidOperationException();
-            //}
+            if (_mCurrentCrc != _mExpectedCrc)
+            {
+                throw new InvalidOperationException();
+            }
             try
             {
                 if (disposing && !_mClosed)
                 {
                     _mClosed = true;
-                    _mCurrentCrc = Crc.Finish(_mCurrentCrc); //now becomes equal
+                    _mCurrentCrc = Crc.Finish(_mCurrentCrc);
 #if DEBUG
                     if (_mCurrentCrc == _mExpectedCrc)
                     {
@@ -55,10 +54,6 @@ namespace SharpCompress.Compressors.LZMA.Utilites
                     }
                     Debug.WriteLine("entropy: " + (int)(entropy * 100) + "%");
 #endif
-                    if (_mCurrentCrc != _mExpectedCrc) //moved test to here
-                    {
-                        throw new InvalidOperationException();
-                    }
                 }
             }
             finally
@@ -107,4 +102,4 @@ namespace SharpCompress.Compressors.LZMA.Utilites
             _mCurrentCrc = Crc.Update(_mCurrentCrc, buffer, offset, count);
         }
     }
-}
+}

src/SharpCompress/Compressors/LZMA/Utilites/Utils.cs

@@ -50,7 +50,7 @@ namespace SharpCompress.Compressors.LZMA.Utilites
                     Debugger.Break();
                 }
 
-                throw new InvalidOperationException("Assertion failed.");
+                throw new Exception("Assertion failed.");
             }
         }
 
@@ -89,4 +89,4 @@ namespace SharpCompress.Compressors.LZMA.Utilites
             }
         }
     }
-}
+}

src/SharpCompress/Compressors/PPMd/H/RangeCoder.cs

@@ -83,7 +83,7 @@ namespace SharpCompress.Compressors.PPMd.H
 
         internal void AriDecNormalize()
         {
-            //		while ((low ^ (low + range)) < TOP || range < BOT && ((range = -low & (BOT - 1)) != 0 ? true : true))
+            //		while ((low ^ (low + range)) < TOP || range < BOT && ((range = -low & (BOT - 1)) != 0 ? true : true)) 
             //		{
             //			code = ((code << 8) | unpackRead.getChar()&0xff)&uintMask;
             //			range = (range << 8)&uintMask;
@@ -118,7 +118,7 @@ namespace SharpCompress.Compressors.PPMd.H
             buffer.Append(_range);
             buffer.Append("\n  subrange=");
             buffer.Append(SubRange);
-            buffer.Append(']');
+            buffer.Append("]");
             return buffer.ToString();
         }
     }
@@ -150,8 +150,8 @@ namespace SharpCompress.Compressors.PPMd.H
             buffer.Append(_highCount);
             buffer.Append("\n  scale=");
             buffer.Append(_scale);
-            buffer.Append(']');
+            buffer.Append("]");
             return buffer.ToString();
         }
     }
-}
+}

src/SharpCompress/Compressors/Rar/RarStream.cs

@@ -1,4 +1,4 @@
-#nullable disable
+#nullable disable
 
 using System;
 using System.IO;
@@ -23,7 +23,6 @@ namespace SharpCompress.Compressors.Rar
         private int outCount;
         private int outTotal;
         private bool isDisposed;
-        private long _position;
 
         public RarStream(IRarUnpack unpack, FileHeader fileHeader, Stream readStream)
         {
@@ -33,7 +32,6 @@ namespace SharpCompress.Compressors.Rar
             fetch = true;
             unpack.DoUnpack(fileHeader, readStream, this);
             fetch = false;
-            _position = 0;
         }
 
         protected override void Dispose(bool disposing)
@@ -58,8 +56,7 @@ namespace SharpCompress.Compressors.Rar
 
         public override long Length => fileHeader.UncompressedSize;
 
-        //commented out code always returned the length of the file
-        public override long Position { get => _position; /* fileHeader.UncompressedSize - unpack.DestSize;*/ set => throw new NotSupportedException(); }
+        public override long Position { get => fileHeader.UncompressedSize - unpack.DestSize; set => throw new NotSupportedException(); }
 
         public override int Read(byte[] buffer, int offset, int count)
         {
@@ -83,7 +80,6 @@ namespace SharpCompress.Compressors.Rar
                 unpack.DoUnpack();
                 fetch = false;
             }
-            _position += (long)outTotal;
             return outTotal;
         }
 
@@ -133,4 +129,4 @@ namespace SharpCompress.Compressors.Rar
             }
         }
     }
-}
+}

src/SharpCompress/Compressors/Xz/Filters/ArmFilter.cs

@@ -1,68 +0,0 @@
-/*
- * ArmFilter.cs -- XZ converter ARM executable
- * <Contribution by Louis-Michel Bergeron, on behalf of aDolus Technolog Inc., 2022>
- * @TODO Properties offset
- */
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using SharpCompress.Compressors.Filters;
-
-namespace SharpCompress.Compressors.Xz.Filters
-{
-    internal class ArmFilter : BlockFilter
-    {
-        public override bool AllowAsLast => false;
-
-        public override bool AllowAsNonLast => true;
-
-        public override bool ChangesDataSize => false;
-
-        private UInt32 _ip = 0;
-
-        //private UInt32 _offset = 0;
-
-        public override void Init(byte[] properties)
-        {
-            if (properties.Length != 0 && properties.Length != 4)
-            {
-                throw new InvalidDataException("ARM properties unexpected length");
-            }
-
-            if (properties.Length == 4)
-            {
-                // Even XZ doesn't support it.
-                throw new InvalidDataException("ARM properties offset is not supported");
-
-                //_offset = BitConverter.ToUInt32(properties, 0);
-                //
-                //if (_offset % (UInt32)BranchExec.Alignment.ARCH_ARM_ALIGNMENT != 0)
-                //{
-                //    throw new InvalidDataException("Filter offset does not match alignment");
-                //}
-            }
-        }
-
-        public override void ValidateFilter()
-        {
-
-        }
-
-        public override int Read(byte[] buffer, int offset, int count)
-        {
-            int bytesRead = BaseStream.Read(buffer, offset, count);
-            BranchExecFilter.ARMConverter(buffer, _ip);
-            _ip += (UInt32)bytesRead;
-            return bytesRead;
-        }
-
-        public override void SetBaseStream(Stream stream)
-        {
-            BaseStream = stream;
-        }
-    }
-}

src/SharpCompress/Compressors/Xz/Filters/ArmThumbFilter.cs

@@ -1,69 +0,0 @@
-/*
- * ArmFThumbFilter.cs -- XZ converter ARMThumb executable
- * <Contribution by Louis-Michel Bergeron, on behalf of aDolus Technolog Inc., 2022>
- * @TODO Properties offset
- */
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using SharpCompress.Compressors.Filters;
-
-namespace SharpCompress.Compressors.Xz.Filters
-{
-    internal class ArmThumbFilter : BlockFilter
-    {
-        public override bool AllowAsLast => false;
-
-        public override bool AllowAsNonLast => true;
-
-        public override bool ChangesDataSize => false;
-
-        private UInt32 _ip = 0;
-
-        //private UInt32 _offset = 0;
-
-        public override void Init(byte[] properties)
-        {
-
-            if (properties.Length != 0 && properties.Length != 4)
-            {
-                throw new InvalidDataException("ARM Thumb properties unexpected length");
-            }
-
-            if (properties.Length == 4)
-            {
-                // Even XZ doesn't support it.
-                throw new InvalidDataException("ARM Thumb properties offset is not supported");
-
-                //_offset = BitConverter.ToUInt32(properties, 0);
-                //
-                //if (_offset % (UInt32)BranchExec.Alignment.ARCH_ARMTHUMB_ALIGNMENT != 0)
-                //{
-                //    throw new InvalidDataException("Filter offset does not match alignment");
-                //}
-            }
-        }
-
-        public override void ValidateFilter()
-        {
-
-        }
-
-        public override int Read(byte[] buffer, int offset, int count)
-        {
-            int bytesRead = BaseStream.Read(buffer, offset, count);
-            BranchExecFilter.ARMTConverter(buffer, _ip);
-            _ip += (UInt32)bytesRead;
-            return bytesRead;
-        }
-
-        public override void SetBaseStream(Stream stream)
-        {
-            BaseStream = stream;
-        }
-    }
-}

src/SharpCompress/Compressors/Xz/Filters/BlockFilter.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 
@@ -20,12 +20,6 @@ namespace SharpCompress.Compressors.Xz.Filters
 
         private static readonly Dictionary<FilterTypes, Type> FilterMap = new Dictionary<FilterTypes, Type>
                                                                           {
-            {FilterTypes.ARCH_x86_FILTER, typeof(X86Filter) },
-            {FilterTypes.ARCH_PowerPC_FILTER, typeof(PowerPCFilter) },
-            {FilterTypes.ARCH_IA64_FILTER, typeof(IA64Filter) },
-            {FilterTypes.ARCH_ARM_FILTER, typeof(ArmFilter) },
-            {FilterTypes.ARCH_ARMTHUMB_FILTER, typeof(ArmThumbFilter) },
-            {FilterTypes.ARCH_SPARC_FILTER, typeof(SparcFilter) },
             {FilterTypes.LZMA2, typeof(Lzma2Filter) }
         };
 

src/SharpCompress/Compressors/Xz/Filters/IA64Filter.cs

@@ -1,67 +0,0 @@
-/*
- * IA64Filter.cs -- XZ converter IA64 executable
- * <Contribution by Louis-Michel Bergeron, on behalf of aDolus Technolog Inc., 2022>
- * @TODO Properties offset
- */
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using SharpCompress.Compressors.Filters;
-
-namespace SharpCompress.Compressors.Xz.Filters
-{
-    internal class IA64Filter : BlockFilter
-    {
-        public override bool AllowAsLast => false;
-
-        public override bool AllowAsNonLast => true;
-
-        public override bool ChangesDataSize => false;
-
-        private UInt32 _ip = 0;
-
-        //private UInt32 _offset = 0;
-
-        public override void Init(byte[] properties)
-        {
-            if (properties.Length != 0 && properties.Length != 4)
-            {
-                throw new InvalidDataException("IA64 properties unexpected length");
-            }
-
-            if (properties.Length == 4)
-            {
-                // Even XZ doesn't support it.
-                throw new InvalidDataException("IA64 properties offset is not supported");
-
-                //_offset = BitConverter.ToUInt32(properties, 0);
-                //
-                //if (_offset % (UInt32)BranchExec.Alignment.ARCH_IA64_ALIGNMENT != 0)
-                //{
-                //    throw new InvalidDataException("Filter offset does not match alignment");
-                //}
-            }
-        }
-
-        public override void ValidateFilter()
-        {
-
-        }
-
-        public override int Read(byte[] buffer, int offset, int count)
-        {
-            int bytesRead = BaseStream.Read(buffer, offset, count);
-            BranchExecFilter.IA64Converter(buffer, _ip);
-            _ip += (UInt32)bytesRead;
-            return bytesRead;
-        }
-        public override void SetBaseStream(Stream stream)
-        {
-            BaseStream = stream;
-        }
-    }
-}

src/SharpCompress/Compressors/Xz/Filters/PowerPCFilter.cs

@@ -1,66 +0,0 @@
-/*
- * PowerPCFilter.cs -- XZ converter PowerPC executable
- * <Contribution by Louis-Michel Bergeron, on behalf of aDolus Technolog Inc., 2022>
- * @TODO Properties offset
- */
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using SharpCompress.Compressors.Filters;
-
-namespace SharpCompress.Compressors.Xz.Filters
-{
-    internal class PowerPCFilter : BlockFilter
-    {
-        public override bool AllowAsLast => false;
-
-        public override bool AllowAsNonLast => true;
-
-        public override bool ChangesDataSize => false;
-
-        private UInt32 _ip = 0;
-
-        //private UInt32 _offset = 0;
-
-        public override void Init(byte[] properties)
-        {
-
-            if (properties.Length != 0 && properties.Length != 4)
-            {
-                throw new InvalidDataException("PPC properties unexpected length");
-            }
-
-            if (properties.Length == 4)
-            {
-                // Even XZ doesn't support it.
-                throw new InvalidDataException("PPC properties offset is not supported");
-
-                //_offset = BitConverter.ToUInt32(properties, 0);
-                //
-                //if (_offset % (UInt32)BranchExec.Alignment.ARCH_PowerPC_ALIGNMENT != 0)
-                //{
-                //    throw new InvalidDataException("Filter offset does not match alignment");
-                //}
-            }
-        }
-
-        public override void ValidateFilter() { }
-
-        public override int Read(byte[] buffer, int offset, int count)
-        {
-            int bytesRead = BaseStream.Read(buffer, offset, count);
-            BranchExecFilter.PowerPCConverter(buffer, _ip);
-            _ip += (UInt32)bytesRead;
-            return bytesRead;
-        }
-
-        public override void SetBaseStream(Stream stream)
-        {
-            BaseStream = stream;
-        }
-    }
-}

src/SharpCompress/Compressors/Xz/Filters/SparcFilter.cs

@@ -1,65 +0,0 @@
-/*
- * SparcFilter.cs -- XZ converter SPARC executable
- * <Contribution by Louis-Michel Bergeron, on behalf of aDolus Technolog Inc., 2022>
- * @TODO Properties offset
- */
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using SharpCompress.Compressors.Filters;
-
-namespace SharpCompress.Compressors.Xz.Filters
-{
-    internal class SparcFilter : BlockFilter
-    {
-        public override bool AllowAsLast => false;
-
-        public override bool AllowAsNonLast => true;
-
-        public override bool ChangesDataSize => false;
-
-        private UInt32 _ip = 0;
-
-        //private UInt32 _offset = 0;
-
-        public override void Init(byte[] properties) {
-
-            if (properties.Length != 0 && properties.Length != 4)
-            {
-                throw new InvalidDataException("SPARC properties unexpected length");
-            }
-
-            if (properties.Length == 4)
-            {
-                // Even XZ doesn't support it.
-                throw new InvalidDataException("SPARC properties offset is not supported");
-
-                //_offset = BitConverter.ToUInt32(properties, 0);
-                //
-                //if (_offset % (UInt32)BranchExec.Alignment.ARCH_SPARC_ALIGNMENT != 0)
-                //{
-                //    throw new InvalidDataException("Filter offset does not match alignment");
-                //}
-            }
-        }
-
-        public override void ValidateFilter() {
-
-        }
-
-        public override int Read(byte[] buffer, int offset, int count){
-            int bytesRead = BaseStream.Read(buffer, offset, count);
-            BranchExecFilter.SPARCConverter(buffer, _ip);
-            _ip += (UInt32)bytesRead;
-            return bytesRead;
-        }
-
-        public override void SetBaseStream(Stream stream) {
-            BaseStream = stream;
-        }
-    }
-}

src/SharpCompress/Compressors/Xz/Filters/X86Filter.cs

@@ -1,70 +0,0 @@
-/*
- * X86Filter.cs -- XZ converter x86 executable
- * <Contribution by Louis-Michel Bergeron, on behalf of aDolus Technolog Inc., 2022>
- * @TODO Properties offset
- */
-
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using SharpCompress.Compressors.Filters;
-
-namespace SharpCompress.Compressors.Xz.Filters
-{
-    internal class X86Filter : BlockFilter
-    {
-        public override bool AllowAsLast => false;
-
-        public override bool AllowAsNonLast => true;
-
-        public override bool ChangesDataSize => false;
-
-        private UInt32 _ip = 0;
-
-        private UInt32 _state = 0;
-
-        //private UInt32 _offset = 0;
-
-        public override void Init(byte[] properties)
-        {
-            if (properties.Length != 0 && properties.Length != 4)
-            {
-                throw new InvalidDataException("X86 properties unexpected length");
-            }
-
-            if (properties.Length == 4)
-            {
-                // Even XZ doesn't support it.
-                throw new InvalidDataException("X86 properties offset is not supported");
-
-                //_offset = BitConverter.ToUInt32(properties, 0);
-                //
-                //if (_offset % (UInt32)BranchExec.Alignment.ARCH_x86_ALIGNMENT != 0)
-                //{
-                //    throw new InvalidDataException("Filter offset does not match alignment");
-                //}
-            }
-        }
-
-        public override void ValidateFilter()
-        {
-
-        }
-
-        public override int Read(byte[] buffer, int offset, int count)
-        {
-            int bytesRead = BaseStream.Read(buffer, offset, count);
-            BranchExecFilter.X86Converter(buffer, _ip, ref _state);
-            _ip += (UInt32)bytesRead;
-            return bytesRead;
-        }
-
-        public override void SetBaseStream(Stream stream)
-        {
-            BaseStream = stream;
-        }
-    }
-}

src/SharpCompress/Compressors/Xz/MultiByteIntegers.cs

@@ -9,7 +9,7 @@ namespace SharpCompress.Compressors.Xz
         {
             if (MaxBytes <= 0)
             {
-                throw new ArgumentOutOfRangeException(nameof(MaxBytes));
+                throw new ArgumentOutOfRangeException();
             }
 
             if (MaxBytes > 9)

src/SharpCompress/Compressors/Zstd/CompressionStream.cs

@@ -0,0 +1,201 @@
+using System;
+using System.Buffers;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+using ZstdSharp.Unsafe;
+
+namespace ZstdSharp
+{
+    public class CompressionStream : Stream
+    {
+        private readonly Stream innerStream;
+        private readonly byte[] outputBuffer;
+        private Compressor compressor;
+        private ZSTD_outBuffer_s output;
+
+        public CompressionStream(Stream stream, int level = Compressor.DefaultCompressionLevel,
+            int bufferSize = 0)
+        {
+            if (stream == null)
+                throw new ArgumentNullException(nameof(stream));
+
+            if (!stream.CanWrite)
+                throw new ArgumentException("Stream is not writable", nameof(stream));
+
+            if (bufferSize < 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize));
+
+            innerStream = stream;
+            compressor = new Compressor(level);
+
+            var outputBufferSize =
+                bufferSize > 0 ? bufferSize : (int) Methods.ZSTD_CStreamOutSize().EnsureZstdSuccess();
+            outputBuffer = ArrayPool<byte>.Shared.Rent(outputBufferSize);
+            output = new ZSTD_outBuffer_s {pos = 0, size = (nuint) outputBufferSize};
+        }
+
+        public void SetParameter(ZSTD_cParameter parameter, int value)
+        {
+            EnsureNotDisposed();
+            compressor.SetParameter(parameter, value);
+        }
+
+        public int GetParameter(ZSTD_cParameter parameter)
+        {
+            EnsureNotDisposed();
+            return compressor.GetParameter(parameter);
+        }
+
+        public void LoadDictionary(byte[] dict)
+        {
+            EnsureNotDisposed();
+            compressor.LoadDictionary(dict);
+        }
+
+        ~CompressionStream() => Dispose(false);
+
+#if !NETSTANDARD2_0 && !NET461
+        public override async ValueTask DisposeAsync()
+#else
+        public async ValueTask DisposeAsync()
+#endif
+        {
+            if (compressor == null)
+                return;
+
+            try
+            {
+                await FlushAsync().ConfigureAwait(false);
+            }
+            finally
+            {
+                ReleaseUnmanagedResources();
+                GC.SuppressFinalize(this);
+            }
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (compressor == null)
+                return;
+
+            try
+            {
+                if (disposing)
+                    Flush();
+            }
+            finally
+            {
+                ReleaseUnmanagedResources();
+            }
+        }
+
+        private void ReleaseUnmanagedResources()
+        {
+            compressor.Dispose();
+            ArrayPool<byte>.Shared.Return(outputBuffer);
+        }
+
+        public override void Flush() 
+            => WriteInternal(null, true);
+
+        public override async Task FlushAsync(CancellationToken cancellationToken)
+            => await WriteInternalAsync(null, true, cancellationToken).ConfigureAwait(false);
+
+        public override void Write(byte[] buffer, int offset, int count)
+            => Write(new ReadOnlySpan<byte>(buffer, offset, count));
+
+#if !NETSTANDARD2_0 && !NET461
+        public override void Write(ReadOnlySpan<byte> buffer)
+            => WriteInternal(buffer, false);
+#else
+        public void Write(ReadOnlySpan<byte> buffer)
+            => WriteInternal(buffer, false);
+#endif
+
+        private void WriteInternal(ReadOnlySpan<byte> buffer, bool lastChunk)
+        {
+            EnsureNotDisposed();
+
+            var input = new ZSTD_inBuffer_s {pos = 0, size = buffer != null ? (nuint) buffer.Length : 0};
+            nuint remaining;
+            do
+            {
+                output.pos = 0;
+                remaining = CompressStream(ref input, buffer,
+                    lastChunk ? ZSTD_EndDirective.ZSTD_e_end : ZSTD_EndDirective.ZSTD_e_continue);
+
+                var written = (int) output.pos;
+                if (written > 0)
+                    innerStream.Write(outputBuffer, 0, written);
+            } while (lastChunk ? remaining > 0 : input.pos < input.size);
+        }
+
+        private async ValueTask WriteInternalAsync(ReadOnlyMemory<byte>? buffer, bool lastChunk,
+            CancellationToken cancellationToken = default)
+        {
+            EnsureNotDisposed();
+
+            var input = new ZSTD_inBuffer_s { pos = 0, size = buffer.HasValue ? (nuint)buffer.Value.Length : 0 };
+            nuint remaining;
+            do
+            {
+                output.pos = 0;
+                remaining = CompressStream(ref input, buffer.HasValue ? buffer.Value.Span : null,
+                    lastChunk ? ZSTD_EndDirective.ZSTD_e_end : ZSTD_EndDirective.ZSTD_e_continue);
+
+                var written = (int) output.pos;
+                if (written > 0)
+                    await innerStream.WriteAsync(outputBuffer, 0, written, cancellationToken).ConfigureAwait(false);
+            } while (lastChunk ? remaining > 0 : input.pos < input.size);
+        }
+
+        public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+            => WriteAsync(new ReadOnlyMemory<byte>(buffer, offset, count), cancellationToken).AsTask();
+
+#if !NETSTANDARD2_0 && !NET461
+        public override async ValueTask WriteAsync(ReadOnlyMemory<byte> buffer,
+            CancellationToken cancellationToken = default)
+            => await WriteInternalAsync(buffer, false, cancellationToken).ConfigureAwait(false);
+#else
+        public async ValueTask WriteAsync(ReadOnlyMemory<byte> buffer,
+            CancellationToken cancellationToken = default)
+            => await WriteInternalAsync(buffer, false, cancellationToken).ConfigureAwait(false);
+#endif
+
+        internal unsafe nuint CompressStream(ref ZSTD_inBuffer_s input, ReadOnlySpan<byte> inputBuffer,
+            ZSTD_EndDirective directive)
+        {
+            fixed (byte* inputBufferPtr = inputBuffer)
+            fixed (byte* outputBufferPtr = outputBuffer)
+            {
+                input.src = inputBufferPtr;
+                output.dst = outputBufferPtr;
+                return compressor.CompressStream(ref input, ref output, directive).EnsureZstdSuccess();
+            }
+        }
+
+        public override bool CanRead => false;
+        public override bool CanSeek => false;
+        public override bool CanWrite => true;
+
+        public override long Length => throw new NotSupportedException();
+
+        public override long Position
+        {
+            get => throw new NotSupportedException();
+            set => throw new NotSupportedException();
+        }
+
+        public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
+        public override void SetLength(long value) => throw new NotSupportedException();
+        public override int Read(byte[] buffer, int offset, int count) => throw new NotSupportedException();
+
+        private void EnsureNotDisposed()
+        {
+            if (compressor == null)
+                throw new ObjectDisposedException(nameof(CompressionStream));
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Compressor.cs

@@ -0,0 +1,164 @@
+using System;
+using ZstdSharp.Unsafe;
+
+namespace ZstdSharp
+{
+    public unsafe class Compressor : IDisposable
+    {
+        public static int MinCompressionLevel => Methods.ZSTD_minCLevel();
+        public static int MaxCompressionLevel => Methods.ZSTD_maxCLevel();
+        public const int DefaultCompressionLevel = 0;
+
+        private int level = DefaultCompressionLevel;
+
+        private ZSTD_CCtx_s* cctx;
+
+        public int Level
+        {
+            get => level;
+            set
+            {
+                if (level != value)
+                {
+                    level = value;
+                    SetParameter(ZSTD_cParameter.ZSTD_c_compressionLevel, value);
+                }
+            }
+        }
+
+        public void SetParameter(ZSTD_cParameter parameter, int value)
+        {
+            EnsureNotDisposed();
+            Methods.ZSTD_CCtx_setParameter(cctx, parameter, value).EnsureZstdSuccess();
+        }
+
+        public int GetParameter(ZSTD_cParameter parameter)
+        {
+            EnsureNotDisposed();
+            int value;
+            Methods.ZSTD_CCtx_getParameter(cctx, parameter, &value).EnsureZstdSuccess();
+            return value;
+        }
+
+        public void LoadDictionary(byte[] dict)
+        {
+            EnsureNotDisposed();
+            if (dict == null)
+            {
+                Methods.ZSTD_CCtx_loadDictionary(cctx, null, 0).EnsureZstdSuccess();
+            }
+            else
+            {
+
+                fixed (byte* dictPtr = dict)
+                    Methods.ZSTD_CCtx_loadDictionary(cctx, dictPtr, (nuint) dict.Length).EnsureZstdSuccess();
+            }
+        }
+
+        public Compressor(int level = DefaultCompressionLevel)
+        {
+            cctx = Methods.ZSTD_createCCtx();
+            if (cctx == null)
+                throw new ZstdException(ZSTD_ErrorCode.ZSTD_error_GENERIC, "Failed to create cctx");
+
+            Level = level;
+        }
+
+        ~Compressor()
+        {
+            ReleaseUnmanagedResources();
+        }
+
+        public static int GetCompressBound(int length) 
+            => (int) Methods.ZSTD_compressBound((nuint) length);
+
+        public static ulong GetCompressBoundLong(ulong length)
+            => Methods.ZSTD_compressBound((nuint) length);
+
+        public Span<byte> Wrap(ReadOnlySpan<byte> src)
+        {
+            var dest = new byte[GetCompressBound(src.Length)];
+            var length = Wrap(src, dest);
+            return new Span<byte>(dest, 0, length);
+        }
+
+        public int Wrap(byte[] src, byte[] dest, int offset)
+            => Wrap(src, new Span<byte>(dest, offset, dest.Length - offset));
+
+        public int Wrap(ReadOnlySpan<byte> src, Span<byte> dest)
+        {
+            EnsureNotDisposed();
+            fixed (byte* srcPtr = src)
+            fixed (byte* destPtr = dest)
+                return (int) Methods
+                    .ZSTD_compress2(cctx, destPtr, (nuint) dest.Length, srcPtr, (nuint) src.Length)
+                    .EnsureZstdSuccess();
+        }
+
+        public int Wrap(ArraySegment<byte> src, ArraySegment<byte> dest) 
+            => Wrap((ReadOnlySpan<byte>) src, dest);
+
+        public int Wrap(byte[] src, int srcOffset, int srcLength, byte[] dst, int dstOffset, int dstLength) 
+            => Wrap(new ReadOnlySpan<byte>(src, srcOffset, srcLength), new Span<byte>(dst, dstOffset, dstLength));
+
+        public bool TryWrap(byte[] src, byte[] dest, int offset, out int written)
+            => TryWrap(src, new Span<byte>(dest, offset, dest.Length - offset), out written);
+
+        public bool TryWrap(ReadOnlySpan<byte> src, Span<byte> dest, out int written)
+        {
+            EnsureNotDisposed();
+            fixed (byte* srcPtr = src)
+            fixed (byte* destPtr = dest)
+            {
+                var returnValue =
+                    Methods.ZSTD_compress2(cctx, destPtr, (nuint) dest.Length, srcPtr, (nuint) src.Length);
+
+                if (returnValue == unchecked(0 - (nuint)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall))
+                {
+                    written = default;
+                    return false;
+                }
+
+                returnValue.EnsureZstdSuccess();
+                written = (int) returnValue;
+                return true;
+            }
+        }
+
+        public bool TryWrap(ArraySegment<byte> src, ArraySegment<byte> dest, out int written)
+            => TryWrap((ReadOnlySpan<byte>)src, dest, out written);
+
+        public bool TryWrap(byte[] src, int srcOffset, int srcLength, byte[] dst, int dstOffset, int dstLength, out int written)
+            => TryWrap(new ReadOnlySpan<byte>(src, srcOffset, srcLength), new Span<byte>(dst, dstOffset, dstLength), out written);
+
+        private void ReleaseUnmanagedResources()
+        {
+            if (cctx != null)
+            {
+                Methods.ZSTD_freeCCtx(cctx);
+                cctx = null;
+            }
+        }
+
+        public void Dispose()
+        {
+            ReleaseUnmanagedResources();
+            GC.SuppressFinalize(this);
+        }
+
+        private void EnsureNotDisposed()
+        {
+            if (cctx == null)
+                throw new ObjectDisposedException(nameof(Compressor));
+        }
+
+        internal nuint CompressStream(ref ZSTD_inBuffer_s input, ref ZSTD_outBuffer_s output, ZSTD_EndDirective directive)
+        {
+            fixed (ZSTD_inBuffer_s* inputPtr = &input)
+            fixed (ZSTD_outBuffer_s* outputPtr = &output)
+            {
+                return Methods.ZSTD_compressStream2(cctx, outputPtr, inputPtr, directive).EnsureZstdSuccess();
+            }
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Constants.cs

@@ -0,0 +1,9 @@
+namespace ZstdSharp
+{
+	internal class Constants
+	{
+		//NOTE: https://docs.microsoft.com/en-us/dotnet/framework/configure-apps/file-schema/runtime/gcallowverylargeobjects-element#remarks
+		//NOTE: https://github.com/dotnet/runtime/blob/v5.0.0-rtm.20519.4/src/libraries/System.Private.CoreLib/src/System/Array.cs#L27
+		public const ulong MaxByteArrayLength = 0x7FFFFFC7;
+	}
+}

src/SharpCompress/Compressors/Zstd/DecompressionStream.cs

@@ -0,0 +1,190 @@
+using System;
+using System.Buffers;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+using ZstdSharp.Unsafe;
+
+namespace ZstdSharp
+{
+    public class DecompressionStream : Stream
+    {
+        private readonly Stream innerStream;
+        private readonly byte[] inputBuffer;
+        private readonly int inputBufferSize;
+        private Decompressor decompressor;
+        private ZSTD_inBuffer_s input;
+        private nuint lastDecompressResult = 0;
+
+        public DecompressionStream(Stream stream, int bufferSize = 0)
+        {
+            if (stream == null)
+                throw new ArgumentNullException(nameof(stream));
+
+            if (!stream.CanRead)
+                throw new ArgumentException("Stream is not readable", nameof(stream));
+
+            if (bufferSize < 0)
+                throw new ArgumentOutOfRangeException(nameof(bufferSize));
+
+            innerStream = stream;
+            decompressor = new Decompressor();
+
+            inputBufferSize = bufferSize > 0 ? bufferSize : (int) Methods.ZSTD_CStreamInSize().EnsureZstdSuccess();
+            inputBuffer = ArrayPool<byte>.Shared.Rent(inputBufferSize);
+            input = new ZSTD_inBuffer_s {pos = (nuint) inputBufferSize, size = (nuint) inputBufferSize};
+        }
+
+        public void SetParameter(ZSTD_dParameter parameter, int value)
+        {
+            EnsureNotDisposed();
+            decompressor.SetParameter(parameter, value);
+        }
+
+        public int GetParameter(ZSTD_dParameter parameter)
+        {
+            EnsureNotDisposed();
+            return decompressor.GetParameter(parameter);
+        }
+
+        public void LoadDictionary(byte[] dict)
+        {
+            EnsureNotDisposed();
+            decompressor.LoadDictionary(dict);
+        }
+
+        ~DecompressionStream() => Dispose(false);
+
+        protected override void Dispose(bool disposing)
+        {
+            if (decompressor == null)
+                return;
+
+            decompressor.Dispose();
+            ArrayPool<byte>.Shared.Return(inputBuffer);
+        }
+
+        public override int Read(byte[] buffer, int offset, int count)
+            => Read(new Span<byte>(buffer, offset, count));
+
+#if !NETSTANDARD2_0 && !NETFRAMEWORK
+        public override int Read(Span<byte> buffer)
+#else
+        public int Read(Span<byte> buffer)
+#endif
+        {
+            EnsureNotDisposed();
+
+            var output = new ZSTD_outBuffer_s {pos = 0, size = (nuint) buffer.Length};
+            while (output.pos < output.size)
+            {
+                if (input.pos >= input.size)
+                {
+                    int bytesRead;
+                    if ((bytesRead = innerStream.Read(inputBuffer, 0, inputBufferSize)) == 0)
+                    {
+                        if (lastDecompressResult != 0)
+                            throw new EndOfStreamException("Premature end of stream");
+
+                        break;
+                    }
+
+                    input.size = (nuint) bytesRead;
+                    input.pos = 0;
+                }
+
+                lastDecompressResult = DecompressStream(ref output, buffer);
+            }
+
+            return (int) output.pos;
+        }
+
+        public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+            => ReadAsync(new Memory<byte>(buffer, offset, count), cancellationToken).AsTask();
+
+#if !NETSTANDARD2_0 && !NET461
+        public override async ValueTask<int> ReadAsync(Memory<byte> buffer,
+            CancellationToken cancellationToken = default)
+#else
+        public async ValueTask<int> ReadAsync(Memory<byte> buffer,
+            CancellationToken cancellationToken = default)
+#endif
+        {
+            EnsureNotDisposed();
+
+            var output = new ZSTD_outBuffer_s { pos = 0, size = (nuint)buffer.Length};
+            while (output.pos < output.size)
+            {
+                if (input.pos >= input.size)
+                {
+                    int bytesRead;
+                    if ((bytesRead = await innerStream.ReadAsync(inputBuffer, 0, inputBufferSize, cancellationToken)
+                        .ConfigureAwait(false)) == 0)
+                    {
+                        if (lastDecompressResult != 0)
+                            throw new EndOfStreamException("Premature end of stream");
+
+                        break;
+                    }
+
+                    input.size = (nuint) bytesRead;
+                    input.pos = 0;
+                }
+
+                lastDecompressResult = DecompressStream(ref output, buffer.Span);
+            }
+
+            return (int) output.pos;
+        }
+
+        private unsafe nuint DecompressStream(ref ZSTD_outBuffer_s output, Span<byte> outputBuffer)
+        {
+            fixed (byte* inputBufferPtr = inputBuffer)
+            fixed (byte* outputBufferPtr = outputBuffer)
+            {
+                input.src = inputBufferPtr;
+                output.dst = outputBufferPtr;
+                return decompressor.DecompressStream(ref input, ref output);
+            }
+        }
+
+        public override bool CanRead => true;
+        public override bool CanSeek => false;
+        public override bool CanWrite => false;
+
+        public override long Length => throw new NotSupportedException();
+
+        public override long Position
+        {
+            get => throw new NotSupportedException();
+            set => throw new NotSupportedException();
+        }
+
+        public override void Flush() => throw new NotSupportedException();
+
+        public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
+        public override void SetLength(long value) => throw new NotSupportedException();
+        public override void Write(byte[] buffer, int offset, int count) => throw new NotSupportedException();
+
+        private void EnsureNotDisposed()
+        {
+            if (decompressor == null)
+                throw new ObjectDisposedException(nameof(DecompressionStream));
+        }
+
+#if NETSTANDARD2_0 || NET461
+        public virtual ValueTask DisposeAsync()
+        {
+            try
+            {
+                Dispose();
+                return default;
+            }
+            catch (Exception exc)
+            {
+                return new ValueTask(Task.FromException(exc));
+            }
+        }
+#endif
+    }
+}

src/SharpCompress/Compressors/Zstd/Decompressor.cs

@@ -0,0 +1,149 @@
+using System;
+using ZstdSharp.Unsafe;
+
+namespace ZstdSharp
+{
+    public unsafe class Decompressor : IDisposable
+    {
+        private ZSTD_DCtx_s* dctx;
+
+        public Decompressor()
+        {
+            dctx = Methods.ZSTD_createDCtx();
+            if (dctx == null)
+                throw new ZstdException(ZSTD_ErrorCode.ZSTD_error_GENERIC, "Failed to create dctx");
+        }
+
+        ~Decompressor()
+        {
+            ReleaseUnmanagedResources();
+        }
+
+        public void SetParameter(ZSTD_dParameter parameter, int value)
+        {
+            EnsureNotDisposed();
+            Methods.ZSTD_DCtx_setParameter(dctx, parameter, value).EnsureZstdSuccess();
+        }
+
+        public int GetParameter(ZSTD_dParameter parameter)
+        {
+            EnsureNotDisposed();
+            int value;
+            Methods.ZSTD_DCtx_getParameter(dctx, parameter, &value).EnsureZstdSuccess();
+            return value;
+        }
+
+        public void LoadDictionary(byte[] dict)
+        {
+            EnsureNotDisposed();
+            if (dict == null)
+            {
+                Methods.ZSTD_DCtx_loadDictionary(dctx, null, 0).EnsureZstdSuccess();
+            }
+            else
+            {
+                fixed (byte* dictPtr = dict)
+                    Methods.ZSTD_DCtx_loadDictionary(dctx, dictPtr, (nuint) dict.Length).EnsureZstdSuccess();
+            }
+        }
+
+        public static ulong GetDecompressedSize(ReadOnlySpan<byte> src)
+        {
+            fixed (byte* srcPtr = src)
+                return Methods.ZSTD_decompressBound(srcPtr, (nuint) src.Length).EnsureContentSizeOk();
+        }
+
+        public static ulong GetDecompressedSize(ArraySegment<byte> src)
+            => GetDecompressedSize((ReadOnlySpan<byte>) src);
+
+        public static ulong GetDecompressedSize(byte[] src, int srcOffset, int srcLength)
+            => GetDecompressedSize(new ReadOnlySpan<byte>(src, srcOffset, srcLength));
+
+        public Span<byte> Unwrap(ReadOnlySpan<byte> src, int maxDecompressedSize = int.MaxValue)
+        {
+            var expectedDstSize = GetDecompressedSize(src);
+            if (expectedDstSize > (ulong) maxDecompressedSize)
+                throw new ZstdException(ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall,
+                    $"Decompressed content size {expectedDstSize} is greater than {nameof(maxDecompressedSize)} {maxDecompressedSize}");
+            if (expectedDstSize > Constants.MaxByteArrayLength)
+                throw new ZstdException(ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall,
+                    $"Decompressed content size {expectedDstSize} is greater than max possible byte array size {Constants.MaxByteArrayLength}");
+
+            var dest = new byte[expectedDstSize];
+            var length = Unwrap(src, dest);
+            return new Span<byte>(dest, 0, length);
+        }
+
+        public int Unwrap(byte[] src, byte[] dest, int offset) 
+            => Unwrap(src, new Span<byte>(dest, offset, dest.Length - offset));
+
+        public int Unwrap(ReadOnlySpan<byte> src, Span<byte> dest)
+        {
+            EnsureNotDisposed();
+            fixed (byte* srcPtr = src)
+            fixed (byte* destPtr = dest)
+                return (int) Methods
+                    .ZSTD_decompressDCtx(dctx, destPtr, (nuint) dest.Length, srcPtr, (nuint) src.Length)
+                    .EnsureZstdSuccess();
+        }
+
+        public int Unwrap(byte[] src, int srcOffset, int srcLength, byte[] dst, int dstOffset, int dstLength)
+            => Unwrap(new ReadOnlySpan<byte>(src, srcOffset, srcLength), new Span<byte>(dst, dstOffset, dstLength));
+
+        public bool TryUnwrap(byte[] src, byte[] dest, int offset, out int written)
+            => TryUnwrap(src, new Span<byte>(dest, offset, dest.Length - offset), out written);
+
+        public bool TryUnwrap(ReadOnlySpan<byte> src, Span<byte> dest, out int written)
+        {
+            EnsureNotDisposed();
+            fixed (byte* srcPtr = src)
+            fixed (byte* destPtr = dest)
+            {
+                var returnValue =
+                    Methods.ZSTD_decompressDCtx(dctx, destPtr, (nuint) dest.Length, srcPtr, (nuint) src.Length);
+
+                if (returnValue == unchecked(0 - (nuint)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall))
+                {
+                    written = default;
+                    return false;
+                }
+
+                returnValue.EnsureZstdSuccess();
+                written = (int) returnValue;
+                return true;
+            }
+        }
+
+        public bool TryUnwrap(byte[] src, int srcOffset, int srcLength, byte[] dst, int dstOffset, int dstLength, out int written)
+            => TryUnwrap(new ReadOnlySpan<byte>(src, srcOffset, srcLength), new Span<byte>(dst, dstOffset, dstLength), out written);
+
+        private void ReleaseUnmanagedResources()
+        {
+            if (dctx != null)
+            {
+                Methods.ZSTD_freeDCtx(dctx);
+                dctx = null;
+            }
+        }
+
+        public void Dispose()
+        {
+            ReleaseUnmanagedResources();
+            GC.SuppressFinalize(this);
+        }
+        private void EnsureNotDisposed()
+        {
+            if (dctx == null)
+                throw new ObjectDisposedException(nameof(Decompressor));
+        }
+
+        internal nuint DecompressStream(ref ZSTD_inBuffer_s input, ref ZSTD_outBuffer_s output)
+        {
+            fixed (ZSTD_inBuffer_s* inputPtr = &input)
+            fixed (ZSTD_outBuffer_s* outputPtr = &output)
+            {
+                return Methods.ZSTD_decompressStream(dctx, outputPtr, inputPtr).EnsureZstdSuccess();
+            }
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/DictBuilder.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using ZstdSharp.Unsafe;
+
+namespace ZstdSharp
+{
+    public static unsafe class DictBuilder
+    {
+        public static byte[] TrainFromBuffer(IEnumerable<byte[]> samples, int dictCapacity = DefaultDictCapacity)
+        {
+            var ms = new MemoryStream();
+            var samplesSizes = samples.Select(sample =>
+            {
+                ms.Write(sample, 0, sample.Length);
+                return (nuint) sample.Length;
+            }).ToArray();
+
+            var dictBuffer = new byte[dictCapacity];
+            fixed (byte* dictBufferPtr = dictBuffer)
+            fixed (byte* samplesBufferPtr = ms.GetBuffer())
+            fixed (nuint* samplesSizesPtr = samplesSizes)
+            {
+                var dictSize = (int) Methods
+                    .ZDICT_trainFromBuffer(dictBufferPtr, (nuint) dictCapacity, samplesBufferPtr, samplesSizesPtr,
+                        (uint) samplesSizes.Length)
+                    .EnsureZdictSuccess();
+
+                if (dictCapacity != dictSize)
+                    Array.Resize(ref dictBuffer, dictSize);
+
+                return dictBuffer;
+            }
+        }
+
+        public const int DefaultDictCapacity = 112640; // Used by zstd utility by default
+    }
+}

src/SharpCompress/Compressors/Zstd/Polyfills/BitOperations.cs

@@ -0,0 +1,201 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !NETCOREAPP3_0_OR_GREATER
+
+using System.Runtime.CompilerServices;
+using static ZstdSharp.UnsafeHelper;
+
+// Some routines inspired by the Stanford Bit Twiddling Hacks by Sean Eron Anderson:
+// http://graphics.stanford.edu/~seander/bithacks.html
+
+namespace System.Numerics
+{
+    /// <summary>
+    /// Utility methods for intrinsic bit-twiddling operations.
+    /// The methods use hardware intrinsics when available on the underlying platform,
+    /// otherwise they use optimized software fallbacks.
+    /// </summary>
+    public static unsafe class BitOperations
+    {
+        // hack: should be public because of inline
+        public static readonly byte* TrailingZeroCountDeBruijn = GetArrayPointer(new byte[]
+        {
+            00, 01, 28, 02, 29, 14, 24, 03,
+            30, 22, 20, 15, 25, 17, 04, 08,
+            31, 27, 13, 23, 21, 19, 16, 07,
+            26, 12, 18, 06, 11, 05, 10, 09
+        });
+
+        // hack: should be public because of inline
+        public static readonly byte* Log2DeBruijn = GetArrayPointer(new byte[]
+        {
+            00, 09, 01, 10, 13, 21, 02, 29,
+            11, 14, 16, 18, 22, 25, 03, 30,
+            08, 12, 20, 28, 15, 17, 24, 07,
+            19, 27, 23, 06, 26, 05, 04, 31
+        });
+
+        /// <summary>
+        /// Returns the integer (floor) log of the specified value, base 2.
+        /// Note that by convention, input value 0 returns 0 since log(0) is undefined.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int Log2(uint value)
+        {
+            // The 0->0 contract is fulfilled by setting the LSB to 1.
+            // Log(1) is 0, and setting the LSB for values > 1 does not change the log2 result.
+            value |= 1;
+
+            // value    lzcnt   actual  expected
+            // ..0001   31      31-31    0
+            // ..0010   30      31-30    1
+            // 0010..    2      31-2    29
+            // 0100..    1      31-1    30
+            // 1000..    0      31-0    31
+
+            // Fallback contract is 0->0
+            // No AggressiveInlining due to large method size
+            // Has conventional contract 0->0 (Log(0) is undefined)
+
+            // Fill trailing zeros with ones, eg 00010010 becomes 00011111
+            value |= value >> 01;
+            value |= value >> 02;
+            value |= value >> 04;
+            value |= value >> 08;
+            value |= value >> 16;
+
+            // uint.MaxValue >> 27 is always in range [0 - 31] so we use Unsafe.AddByteOffset to avoid bounds check
+            return Log2DeBruijn[
+                // Using deBruijn sequence, k=2, n=5 (2^5=32) : 0b_0000_0111_1100_0100_1010_1100_1101_1101u
+                (int)((value * 0x07C4ACDDu) >> 27)];
+        }
+
+        /// <summary>
+        /// Returns the integer (floor) log of the specified value, base 2.
+        /// Note that by convention, input value 0 returns 0 since log(0) is undefined.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int Log2(ulong value)
+        {
+            value |= 1;
+
+            uint hi = (uint)(value >> 32);
+
+            if (hi == 0)
+            {
+                return Log2((uint)value);
+            }
+
+            return 32 + Log2(hi);
+        }
+
+        /// <summary>
+        /// Count the number of trailing zero bits in an integer value.
+        /// Similar in behavior to the x86 instruction TZCNT.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int TrailingZeroCount(int value)
+            => TrailingZeroCount((uint)value);
+
+        /// <summary>
+        /// Count the number of trailing zero bits in an integer value.
+        /// Similar in behavior to the x86 instruction TZCNT.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int TrailingZeroCount(uint value)
+        {
+            // Unguarded fallback contract is 0->0, BSF contract is 0->undefined
+            if (value == 0)
+            {
+                return 32;
+            }
+
+            // uint.MaxValue >> 27 is always in range [0 - 31] so we use Unsafe.AddByteOffset to avoid bounds check
+            return TrailingZeroCountDeBruijn[
+                // Using deBruijn sequence, k=2, n=5 (2^5=32) : 0b_0000_0111_0111_1100_1011_0101_0011_0001u
+                (int)(((value & (uint)-(int)value) * 0x077CB531u) >> 27)]; // Multi-cast mitigates redundant conv.u8
+        }
+
+        /// <summary>
+        /// Count the number of trailing zero bits in a mask.
+        /// Similar in behavior to the x86 instruction TZCNT.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int TrailingZeroCount(long value)
+            => TrailingZeroCount((ulong)value);
+
+        /// <summary>
+        /// Count the number of trailing zero bits in a mask.
+        /// Similar in behavior to the x86 instruction TZCNT.
+        /// </summary>
+        /// <param name="value">The value.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static int TrailingZeroCount(ulong value)
+        {
+            uint lo = (uint)value;
+
+            if (lo == 0)
+            {
+                return 32 + TrailingZeroCount((uint)(value >> 32));
+            }
+
+            return TrailingZeroCount(lo);
+        }
+
+        /// <summary>
+        /// Rotates the specified value left by the specified number of bits.
+        /// Similar in behavior to the x86 instruction ROL.
+        /// </summary>
+        /// <param name="value">The value to rotate.</param>
+        /// <param name="offset">The number of bits to rotate by.
+        /// Any value outside the range [0..31] is treated as congruent mod 32.</param>
+        /// <returns>The rotated value.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static uint RotateLeft(uint value, int offset)
+            => (value << offset) | (value >> (32 - offset));
+
+        /// <summary>
+        /// Rotates the specified value left by the specified number of bits.
+        /// Similar in behavior to the x86 instruction ROL.
+        /// </summary>
+        /// <param name="value">The value to rotate.</param>
+        /// <param name="offset">The number of bits to rotate by.
+        /// Any value outside the range [0..63] is treated as congruent mod 64.</param>
+        /// <returns>The rotated value.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ulong RotateLeft(ulong value, int offset)
+            => (value << offset) | (value >> (64 - offset));
+
+        /// <summary>
+        /// Rotates the specified value right by the specified number of bits.
+        /// Similar in behavior to the x86 instruction ROR.
+        /// </summary>
+        /// <param name="value">The value to rotate.</param>
+        /// <param name="offset">The number of bits to rotate by.
+        /// Any value outside the range [0..31] is treated as congruent mod 32.</param>
+        /// <returns>The rotated value.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static uint RotateRight(uint value, int offset)
+            => (value >> offset) | (value << (32 - offset));
+
+        /// <summary>
+        /// Rotates the specified value right by the specified number of bits.
+        /// Similar in behavior to the x86 instruction ROR.
+        /// </summary>
+        /// <param name="value">The value to rotate.</param>
+        /// <param name="offset">The number of bits to rotate by.
+        /// Any value outside the range [0..63] is treated as congruent mod 64.</param>
+        /// <returns>The rotated value.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ulong RotateRight(ulong value, int offset)
+            => (value >> offset) | (value << (64 - offset));
+    }
+}
+
+#endif

src/SharpCompress/Compressors/Zstd/Polyfills/SkipLocalsInitAttribute.cs

@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !NET5_0_OR_GREATER
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Used to indicate to the compiler that the <c>.locals init</c> flag should not be set in method headers.
+    /// </summary>
+    /// <remarks>Internal copy of the .NET 5 attribute.</remarks>
+    [AttributeUsage(
+        AttributeTargets.Module |
+        AttributeTargets.Class |
+        AttributeTargets.Struct |
+        AttributeTargets.Interface |
+        AttributeTargets.Constructor |
+        AttributeTargets.Method |
+        AttributeTargets.Property |
+        AttributeTargets.Event,
+        Inherited = false)]
+    internal sealed class SkipLocalsInitAttribute : Attribute
+    {
+    }
+}
+#endif

src/SharpCompress/Compressors/Zstd/Polyfills/Vector128.cs

@@ -0,0 +1,54 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !NETCOREAPP3_0_OR_GREATER
+
+using System.Runtime.CompilerServices;
+
+namespace System.Runtime.Intrinsics
+{
+    public static class Vector128
+    {
+        internal const int Size = 16;
+
+        public static unsafe Vector128<byte> Create(byte value)
+        {
+            byte* pResult = stackalloc byte[16]
+            {
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+                value,
+            };
+
+            return Unsafe.AsRef<Vector128<byte>>(pResult);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<U> As<T, U>(this Vector128<T> vector)
+            where T : struct
+            where U : struct =>
+            Unsafe.As<Vector128<T>, Vector128<U>>(ref vector);
+
+        public static T GetElement<T>(this Vector128<T> vector, int index)
+            where T : struct
+        {
+            ref T e0 = ref Unsafe.As<Vector128<T>, T>(ref vector);
+            return Unsafe.Add(ref e0, index);
+        }
+    }
+}
+
+#endif

src/SharpCompress/Compressors/Zstd/Polyfills/Vector128_1.cs

@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if !NETCOREAPP3_0_OR_GREATER
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace System.Runtime.Intrinsics
+{
+    [StructLayout(LayoutKind.Sequential, Size = Vector128.Size)]
+    public readonly struct Vector128<T> : IEquatable<Vector128<T>>
+        where T : struct
+    {
+        private readonly ulong _00;
+        private readonly ulong _01;
+
+        public static int Count => Vector128.Size / Unsafe.SizeOf<T>();
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool Equals(Vector128<T> other)
+        {
+            for (int i = 0; i < Count; i++)
+            {
+                if (!((IEquatable<T>)(this.GetElement(i))).Equals(other.GetElement(i)))
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+    }
+}
+
+#endif

src/SharpCompress/Compressors/Zstd/ThrowHelper.cs

@@ -0,0 +1,43 @@
+using ZstdSharp.Unsafe;
+
+namespace ZstdSharp
+{
+    public static unsafe class ThrowHelper
+    {
+        private const ulong ZSTD_CONTENTSIZE_UNKNOWN = unchecked(0UL - 1);
+        private const ulong ZSTD_CONTENTSIZE_ERROR = unchecked(0UL - 2);
+
+        public static nuint EnsureZstdSuccess(this nuint returnValue)
+        {
+            if (Methods.ZSTD_isError(returnValue) != 0)
+                ThrowException(returnValue, Methods.ZSTD_getErrorName(returnValue));
+
+            return returnValue;
+        }
+
+        public static nuint EnsureZdictSuccess(this nuint returnValue)
+        {
+            if (Methods.ZDICT_isError(returnValue) != 0)
+                ThrowException(returnValue, Methods.ZDICT_getErrorName(returnValue));
+
+            return returnValue;
+        }
+
+        public static ulong EnsureContentSizeOk(this ulong returnValue)
+        {
+            if (returnValue == ZSTD_CONTENTSIZE_UNKNOWN)
+                throw new ZstdException(ZSTD_ErrorCode.ZSTD_error_GENERIC, "Decompressed content size is not specified");
+
+            if (returnValue == ZSTD_CONTENTSIZE_ERROR)
+                throw new ZstdException(ZSTD_ErrorCode.ZSTD_error_GENERIC, "Decompressed content size cannot be determined (e.g. invalid magic number, srcSize too small)");
+
+            return returnValue;
+        }
+
+        private static void ThrowException(nuint returnValue, string message)
+        {
+            var code = 0 - returnValue;
+            throw new ZstdException((ZSTD_ErrorCode) code, message);
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/Arrays.cs

@@ -0,0 +1,368 @@
+using System;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        static uint* rtbTable = GetArrayPointer(new uint[8] {
+            0,
+            473195,
+            504333,
+            520860,
+            550000,
+            700000,
+            750000,
+            830000,
+        });
+        static byte* LL_Code = GetArrayPointer(new byte[64] 
+        {
+            0,
+            1,
+            2,
+            3,
+            4,
+            5,
+            6,
+            7,
+            8,
+            9,
+            10,
+            11,
+            12,
+            13,
+            14,
+            15,
+            16,
+            16,
+            17,
+            17,
+            18,
+            18,
+            19,
+            19,
+            20,
+            20,
+            20,
+            20,
+            21,
+            21,
+            21,
+            21,
+            22,
+            22,
+            22,
+            22,
+            22,
+            22,
+            22,
+            22,
+            23,
+            23,
+            23,
+            23,
+            23,
+            23,
+            23,
+            23,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+            24,
+        });
+        static byte* ML_Code = GetArrayPointer(new byte[128] 
+        {
+            0,
+            1,
+            2,
+            3,
+            4,
+            5,
+            6,
+            7,
+            8,
+            9,
+            10,
+            11,
+            12,
+            13,
+            14,
+            15,
+            16,
+            17,
+            18,
+            19,
+            20,
+            21,
+            22,
+            23,
+            24,
+            25,
+            26,
+            27,
+            28,
+            29,
+            30,
+            31,
+            32,
+            32,
+            33,
+            33,
+            34,
+            34,
+            35,
+            35,
+            36,
+            36,
+            36,
+            36,
+            37,
+            37,
+            37,
+            37,
+            38,
+            38,
+            38,
+            38,
+            38,
+            38,
+            38,
+            38,
+            39,
+            39,
+            39,
+            39,
+            39,
+            39,
+            39,
+            39,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            40,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            41,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+            42,
+        });
+        static ulong* srcSizeTiers = GetArrayPointer(new ulong[4] 
+        {
+            16 * (1 << 10),
+            128 * (1 << 10),
+            256 * (1 << 10),
+            (unchecked(0UL - 1)),
+        });
+        static ZSTD_blockCompressor?[][] blockCompressor = new ZSTD_blockCompressor?[4][] 
+                                                           {
+                                                               new ZSTD_blockCompressor[10]
+                                                               {
+                                                                   ZSTD_compressBlock_fast,
+                                                                   ZSTD_compressBlock_fast,
+                                                                   ZSTD_compressBlock_doubleFast,
+                                                                   ZSTD_compressBlock_greedy,
+                                                                   ZSTD_compressBlock_lazy,
+                                                                   ZSTD_compressBlock_lazy2,
+                                                                   ZSTD_compressBlock_btlazy2,
+                                                                   ZSTD_compressBlock_btopt,
+                                                                   ZSTD_compressBlock_btultra,
+                                                                   ZSTD_compressBlock_btultra2,
+                                                               },
+                                                               new ZSTD_blockCompressor[10]
+                                                               {
+                                                                   ZSTD_compressBlock_fast_extDict,
+                                                                   ZSTD_compressBlock_fast_extDict,
+                                                                   ZSTD_compressBlock_doubleFast_extDict,
+                                                                   ZSTD_compressBlock_greedy_extDict,
+                                                                   ZSTD_compressBlock_lazy_extDict,
+                                                                   ZSTD_compressBlock_lazy2_extDict,
+                                                                   ZSTD_compressBlock_btlazy2_extDict,
+                                                                   ZSTD_compressBlock_btopt_extDict,
+                                                                   ZSTD_compressBlock_btultra_extDict,
+                                                                   ZSTD_compressBlock_btultra_extDict,
+                                                               },
+                                                               new ZSTD_blockCompressor[10]
+                                                               {
+                                                                   ZSTD_compressBlock_fast_dictMatchState,
+                                                                   ZSTD_compressBlock_fast_dictMatchState,
+                                                                   ZSTD_compressBlock_doubleFast_dictMatchState,
+                                                                   ZSTD_compressBlock_greedy_dictMatchState,
+                                                                   ZSTD_compressBlock_lazy_dictMatchState,
+                                                                   ZSTD_compressBlock_lazy2_dictMatchState,
+                                                                   ZSTD_compressBlock_btlazy2_dictMatchState,
+                                                                   ZSTD_compressBlock_btopt_dictMatchState,
+                                                                   ZSTD_compressBlock_btultra_dictMatchState,
+                                                                   ZSTD_compressBlock_btultra_dictMatchState,
+                                                               },
+                                                               new ZSTD_blockCompressor?[10]
+                                                               {
+                                                                   null,
+                                                                   null,
+                                                                   null,
+                                                                   ZSTD_compressBlock_greedy_dedicatedDictSearch,
+                                                                   ZSTD_compressBlock_lazy_dedicatedDictSearch,
+                                                                   ZSTD_compressBlock_lazy2_dedicatedDictSearch,
+                                                                   null,
+                                                                   null,
+                                                                   null,
+                                                                   null,
+                                                               },
+                                                           };
+        static ZSTD_blockCompressor[][] rowBasedBlockCompressors = new ZSTD_blockCompressor[4][] 
+        {
+            new ZSTD_blockCompressor[3]
+            {
+                ZSTD_compressBlock_greedy_row,
+                ZSTD_compressBlock_lazy_row,
+                ZSTD_compressBlock_lazy2_row,
+            },
+            new ZSTD_blockCompressor[3]
+            {
+                ZSTD_compressBlock_greedy_extDict_row,
+                ZSTD_compressBlock_lazy_extDict_row,
+                ZSTD_compressBlock_lazy2_extDict_row,
+            },
+            new ZSTD_blockCompressor[3]
+            {
+                ZSTD_compressBlock_greedy_dictMatchState_row,
+                ZSTD_compressBlock_lazy_dictMatchState_row,
+                ZSTD_compressBlock_lazy2_dictMatchState_row,
+            },
+            new ZSTD_blockCompressor[3]
+            {
+                ZSTD_compressBlock_greedy_dedicatedDictSearch_row,
+                ZSTD_compressBlock_lazy_dedicatedDictSearch_row,
+                ZSTD_compressBlock_lazy2_dedicatedDictSearch_row,
+            },
+        };
+        static searchMax_f?[][] searchFuncs = new searchMax_f?[4][] 
+                                              {
+                                                  new searchMax_f[3]
+                                                  {
+                                                      ZSTD_HcFindBestMatch_selectMLS,
+                                                      ZSTD_BtFindBestMatch_selectMLS,
+                                                      ZSTD_RowFindBestMatch_selectRowLog,
+                                                  },
+                                                  new searchMax_f?[3]
+                                                  {
+                                                      null,
+                                                      null,
+                                                      null,
+                                                  },
+                                                  new searchMax_f[3]
+                                                  {
+                                                      ZSTD_HcFindBestMatch_dictMatchState_selectMLS,
+                                                      ZSTD_BtFindBestMatch_dictMatchState_selectMLS,
+                                                      ZSTD_RowFindBestMatch_dictMatchState_selectRowLog,
+                                                  },
+                                                  new searchMax_f?[3]
+                                                  {
+                                                      ZSTD_HcFindBestMatch_dedicatedDictSearch_selectMLS,
+                                                      null,
+                                                      ZSTD_RowFindBestMatch_dedicatedDictSearch_selectRowLog,
+                                                  },
+                                              };
+        static searchMax_f[] searchFuncsExtGeneric = new searchMax_f[3] 
+        {
+            ZSTD_HcFindBestMatch_extDict_selectMLS,
+            ZSTD_BtFindBestMatch_extDict_selectMLS,
+            ZSTD_RowFindBestMatch_extDict_selectRowLog,
+        };
+        static decompressionAlgo[] decompress = new decompressionAlgo[2] 
+        {
+            HUF_decompress4X1,
+            HUF_decompress4X2,
+        };
+        static uint* dec32table = GetArrayPointer(new uint[8] 
+        {
+            0,
+            1,
+            2,
+            1,
+            4,
+            4,
+            4,
+            4,
+        });
+        static int* dec64table = GetArrayPointer(new int[8] 
+        {
+            8,
+            8,
+            8,
+            7,
+            8,
+            9,
+            10,
+            11,
+        });
+
+        private static byte* emptyString = GetArrayPointer(new byte[] {0});
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/BIT_CStream_t.cs

@@ -0,0 +1,24 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /*-******************************************
+    *  bitStream encoding API (write forward)
+    ********************************************/
+    /* bitStream can mix input from multiple sources.
+     * A critical property of these streams is that they encode and decode in **reverse** direction.
+     * So the first bit sequence you add will be the last to be read, like a LIFO stack.
+     */
+    public unsafe partial struct BIT_CStream_t
+    {
+        public nuint bitContainer;
+
+        public uint bitPos;
+
+        public sbyte* startPtr;
+
+        public sbyte* ptr;
+
+        public sbyte* endPtr;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/BIT_DStream_status.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public enum BIT_DStream_status
+    {
+        BIT_DStream_unfinished = 0,
+        BIT_DStream_endOfBuffer = 1,
+        BIT_DStream_completed = 2,
+        BIT_DStream_overflow = 3,
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/BIT_DStream_t.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /*-********************************************
+    *  bitStream decoding API (read backward)
+    **********************************************/
+    public unsafe partial struct BIT_DStream_t
+    {
+        public nuint bitContainer;
+
+        public uint bitsConsumed;
+
+        public sbyte* ptr;
+
+        public sbyte* start;
+
+        public sbyte* limitPtr;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/Bitstream.cs

@@ -0,0 +1,420 @@
+using System;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        /*-**************************************************************
+        *  Internal functions
+        ****************************************************************/
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        [InlineMethod.Inline]
+        private static uint BIT_highbit32(uint val)
+        {
+            assert(val != 0);
+
+            {
+                return (uint) BitOperations.Log2(val);
+            }
+        }
+
+        public static uint* BIT_mask = GetArrayPointer(new uint[32]
+        {
+            0,
+            1,
+            3,
+            7,
+            0xF,
+            0x1F,
+            0x3F,
+            0x7F,
+            0xFF,
+            0x1FF,
+            0x3FF,
+            0x7FF,
+            0xFFF,
+            0x1FFF,
+            0x3FFF,
+            0x7FFF,
+            0xFFFF,
+            0x1FFFF,
+            0x3FFFF,
+            0x7FFFF,
+            0xFFFFF,
+            0x1FFFFF,
+            0x3FFFFF,
+            0x7FFFFF,
+            0xFFFFFF,
+            0x1FFFFFF,
+            0x3FFFFFF,
+            0x7FFFFFF,
+            0xFFFFFFF,
+            0x1FFFFFFF,
+            0x3FFFFFFF,
+            0x7FFFFFFF,
+        });
+
+        /*-**************************************************************
+        *  bitStream encoding
+        ****************************************************************/
+        /*! BIT_initCStream() :
+         *  `dstCapacity` must be > sizeof(size_t)
+         *  @return : 0 if success,
+         *            otherwise an error code (can be tested using ERR_isError()) */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_initCStream(BIT_CStream_t* bitC, void* startPtr, nuint dstCapacity)
+        {
+            bitC->bitContainer = 0;
+            bitC->bitPos = 0;
+            bitC->startPtr = (sbyte*)(startPtr);
+            bitC->ptr = bitC->startPtr;
+            bitC->endPtr = bitC->startPtr + dstCapacity - (nuint)(sizeof(nuint));
+            if (dstCapacity <= (nuint)(sizeof(nuint)))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+            }
+
+            return 0;
+        }
+
+        /*! BIT_addBits() :
+         *  can add up to 31 bits into `bitC`.
+         *  Note : does not check for register overflow ! */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void BIT_addBits(BIT_CStream_t* bitC, nuint value, uint nbBits)
+        {
+            assert(nbBits < ((nuint)(sizeof(uint) * 32) / (nuint)(sizeof(uint))));
+            assert(nbBits + bitC->bitPos < (nuint)(sizeof(nuint)) * 8);
+            bitC->bitContainer |= (value & BIT_mask[nbBits]) << (int)bitC->bitPos;
+            bitC->bitPos += nbBits;
+        }
+
+        /*! BIT_addBitsFast() :
+         *  works only if `value` is _clean_,
+         *  meaning all high bits above nbBits are 0 */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void BIT_addBitsFast(BIT_CStream_t* bitC, nuint value, uint nbBits)
+        {
+            assert((value >> (int)nbBits) == 0);
+            assert(nbBits + bitC->bitPos < (nuint)(sizeof(nuint)) * 8);
+            bitC->bitContainer |= value << (int)bitC->bitPos;
+            bitC->bitPos += nbBits;
+        }
+
+        /*! BIT_flushBitsFast() :
+         *  assumption : bitContainer has not overflowed
+         *  unsafe version; does not check buffer overflow */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void BIT_flushBitsFast(BIT_CStream_t* bitC)
+        {
+            nuint nbBytes = bitC->bitPos >> 3;
+
+            assert(bitC->bitPos < (nuint)(sizeof(nuint)) * 8);
+            assert(bitC->ptr <= bitC->endPtr);
+            MEM_writeLEST((void*)bitC->ptr, bitC->bitContainer);
+            bitC->ptr += nbBytes;
+            bitC->bitPos &= 7;
+            bitC->bitContainer >>= (int)(nbBytes * 8);
+        }
+
+        /*! BIT_flushBits() :
+         *  assumption : bitContainer has not overflowed
+         *  safe version; check for buffer overflow, and prevents it.
+         *  note : does not signal buffer overflow.
+         *  overflow will be revealed later on using BIT_closeCStream() */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void BIT_flushBits(BIT_CStream_t* bitC)
+        {
+            nuint nbBytes = bitC->bitPos >> 3;
+
+            assert(bitC->bitPos < (nuint)(sizeof(nuint)) * 8);
+            assert(bitC->ptr <= bitC->endPtr);
+            MEM_writeLEST((void*)bitC->ptr, bitC->bitContainer);
+            bitC->ptr += nbBytes;
+            if (bitC->ptr > bitC->endPtr)
+            {
+                bitC->ptr = bitC->endPtr;
+            }
+
+            bitC->bitPos &= 7;
+            bitC->bitContainer >>= (int)(nbBytes * 8);
+        }
+
+        /*! BIT_closeCStream() :
+         *  @return : size of CStream, in bytes,
+         *            or 0 if it could not fit into dstBuffer */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_closeCStream(BIT_CStream_t* bitC)
+        {
+            BIT_addBitsFast(bitC, 1, 1);
+            BIT_flushBits(bitC);
+            if (bitC->ptr >= bitC->endPtr)
+            {
+                return 0;
+            }
+
+            return (nuint)((bitC->ptr - bitC->startPtr) + (((bitC->bitPos > 0)) ? 1 : 0));
+        }
+
+        /*-********************************************************
+        *  bitStream decoding
+        **********************************************************/
+        /*! BIT_initDStream() :
+         *  Initialize a BIT_DStream_t.
+         * `bitD` : a pointer to an already allocated BIT_DStream_t structure.
+         * `srcSize` must be the *exact* size of the bitStream, in bytes.
+         * @return : size of stream (== srcSize), or an errorCode if a problem is detected
+         */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_initDStream(BIT_DStream_t* bitD, void* srcBuffer, nuint srcSize)
+        {
+            if (srcSize < 1)
+            {
+                memset((void*)(bitD), (0), ((nuint)(sizeof(BIT_DStream_t))));
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+            }
+
+            bitD->start = (sbyte*)(srcBuffer);
+            bitD->limitPtr = bitD->start + (nuint)(sizeof(nuint));
+            if (srcSize >= (nuint)(sizeof(nuint)))
+            {
+                bitD->ptr = (sbyte*)(srcBuffer) + srcSize - (nuint)(sizeof(nuint));
+                bitD->bitContainer = MEM_readLEST((void*)bitD->ptr);
+
+                {
+                    byte lastByte = ((byte*)(srcBuffer))[srcSize - 1];
+
+                    bitD->bitsConsumed = lastByte != 0 ? 8 - BIT_highbit32(lastByte) : 0;
+                    if (lastByte == 0)
+                    {
+                        return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+                    }
+                }
+            }
+            else
+            {
+                bitD->ptr = bitD->start;
+                bitD->bitContainer = *(byte*)(bitD->start);
+                switch (srcSize)
+                {
+                    case 7:
+                    {
+                        bitD->bitContainer += (nuint)(((byte*)(srcBuffer))[6]) << (int)((nuint)(sizeof(nuint)) * 8 - 16);
+                    }
+
+
+                    goto case 6;
+                    case 6:
+                    {
+                        bitD->bitContainer += (nuint)(((byte*)(srcBuffer))[5]) << (int)((nuint)(sizeof(nuint)) * 8 - 24);
+                    }
+
+
+                    goto case 5;
+                    case 5:
+                    {
+                        bitD->bitContainer += (nuint)(((byte*)(srcBuffer))[4]) << (int)((nuint)(sizeof(nuint)) * 8 - 32);
+                    }
+
+
+                    goto case 4;
+                    case 4:
+                    {
+                        bitD->bitContainer += (nuint)(((byte*)(srcBuffer))[3]) << 24;
+                    }
+
+
+                    goto case 3;
+                    case 3:
+                    {
+                        bitD->bitContainer += (nuint)(((byte*)(srcBuffer))[2]) << 16;
+                    }
+
+
+                    goto case 2;
+                    case 2:
+                    {
+                        bitD->bitContainer += (nuint)(((byte*)(srcBuffer))[1]) << 8;
+                    }
+
+
+                    goto default;
+                    default:
+                    {
+                        break;
+                    }
+                }
+
+
+                {
+                    byte lastByte = ((byte*)(srcBuffer))[srcSize - 1];
+
+                    bitD->bitsConsumed = lastByte != 0 ? 8 - BIT_highbit32(lastByte) : 0;
+                    if (lastByte == 0)
+                    {
+                        return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+                    }
+                }
+
+                bitD->bitsConsumed += (uint)((nuint)(sizeof(nuint)) - srcSize) * 8;
+            }
+
+            return srcSize;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_getUpperBits(nuint bitContainer, uint start)
+        {
+            return bitContainer >> (int)start;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_getMiddleBits(nuint bitContainer, uint start, uint nbBits)
+        {
+            uint regMask = (uint)((nuint)(sizeof(nuint)) * 8 - 1);
+
+            assert(nbBits < ((nuint)(sizeof(uint) * 32) / (nuint)(sizeof(uint))));
+            return (bitContainer >> (int)(start & regMask)) & BIT_mask[nbBits];
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_getLowerBits(nuint bitContainer, uint nbBits)
+        {
+            assert(nbBits < ((nuint)(sizeof(uint) * 32) / (nuint)(sizeof(uint))));
+            return bitContainer & BIT_mask[nbBits];
+        }
+
+        /*! BIT_lookBits() :
+         *  Provides next n bits from local register.
+         *  local register is not modified.
+         *  On 32-bits, maxNbBits==24.
+         *  On 64-bits, maxNbBits==56.
+         * @return : value extracted */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_lookBits(BIT_DStream_t* bitD, uint nbBits)
+        {
+            return BIT_getMiddleBits(bitD->bitContainer, (uint)(((nuint)(sizeof(nuint)) * 8) - bitD->bitsConsumed - nbBits), nbBits);
+        }
+
+        /*! BIT_lookBitsFast() :
+         *  unsafe version; only works if nbBits >= 1 */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_lookBitsFast(BIT_DStream_t* bitD, uint nbBits)
+        {
+            uint regMask = (uint)((nuint)(sizeof(nuint)) * 8 - 1);
+
+            assert(nbBits >= 1);
+            return (bitD->bitContainer << (int)(bitD->bitsConsumed & regMask)) >> (int)(((regMask + 1) - nbBits) & regMask);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void BIT_skipBits(BIT_DStream_t* bitD, uint nbBits)
+        {
+            bitD->bitsConsumed += nbBits;
+        }
+
+        /*! BIT_readBits() :
+         *  Read (consume) next n bits from local register and update.
+         *  Pay attention to not read more than nbBits contained into local register.
+         * @return : extracted value. */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_readBits(BIT_DStream_t* bitD, uint nbBits)
+        {
+            nuint value = BIT_lookBits(bitD, nbBits);
+
+            BIT_skipBits(bitD, nbBits);
+            return value;
+        }
+
+        /*! BIT_readBitsFast() :
+         *  unsafe version; only works only if nbBits >= 1 */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint BIT_readBitsFast(BIT_DStream_t* bitD, uint nbBits)
+        {
+            nuint value = BIT_lookBitsFast(bitD, nbBits);
+
+            assert(nbBits >= 1);
+            BIT_skipBits(bitD, nbBits);
+            return value;
+        }
+
+        /*! BIT_reloadDStreamFast() :
+         *  Similar to BIT_reloadDStream(), but with two differences:
+         *  1. bitsConsumed <= sizeof(bitD->bitContainer)*8 must hold!
+         *  2. Returns BIT_DStream_overflow when bitD->ptr < bitD->limitPtr, at this
+         *     point you must use BIT_reloadDStream() to reload.
+         */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static BIT_DStream_status BIT_reloadDStreamFast(BIT_DStream_t* bitD)
+        {
+            if ((bitD->ptr < bitD->limitPtr))
+            {
+                return BIT_DStream_status.BIT_DStream_overflow;
+            }
+
+            assert(bitD->bitsConsumed <= (nuint)(sizeof(nuint)) * 8);
+            bitD->ptr -= bitD->bitsConsumed >> 3;
+            bitD->bitsConsumed &= 7;
+            bitD->bitContainer = MEM_readLEST((void*)bitD->ptr);
+            return BIT_DStream_status.BIT_DStream_unfinished;
+        }
+
+        /*! BIT_reloadDStream() :
+         *  Refill `bitD` from buffer previously set in BIT_initDStream() .
+         *  This function is safe, it guarantees it will not read beyond src buffer.
+         * @return : status of `BIT_DStream_t` internal register.
+         *           when status == BIT_DStream_unfinished, internal register is filled with at least 25 or 57 bits */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD)
+        {
+            if (bitD->bitsConsumed > ((nuint)(sizeof(nuint)) * 8))
+            {
+                return BIT_DStream_status.BIT_DStream_overflow;
+            }
+
+            if (bitD->ptr >= bitD->limitPtr)
+            {
+                return BIT_reloadDStreamFast(bitD);
+            }
+
+            if (bitD->ptr == bitD->start)
+            {
+                if (bitD->bitsConsumed < (nuint)(sizeof(nuint)) * 8)
+                {
+                    return BIT_DStream_status.BIT_DStream_endOfBuffer;
+                }
+
+                return BIT_DStream_status.BIT_DStream_completed;
+            }
+
+
+            {
+                uint nbBytes = bitD->bitsConsumed >> 3;
+                BIT_DStream_status result = BIT_DStream_status.BIT_DStream_unfinished;
+
+                if (bitD->ptr - nbBytes < bitD->start)
+                {
+                    nbBytes = (uint)(bitD->ptr - bitD->start);
+                    result = BIT_DStream_status.BIT_DStream_endOfBuffer;
+                }
+
+                bitD->ptr -= nbBytes;
+                bitD->bitsConsumed -= nbBytes * 8;
+                bitD->bitContainer = MEM_readLEST((void*)bitD->ptr);
+                return result;
+            }
+        }
+
+        /*! BIT_endOfDStream() :
+         * @return : 1 if DStream has _exactly_ reached its end (all bits consumed).
+         */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint BIT_endOfDStream(BIT_DStream_t* DStream)
+        {
+            return ((((DStream->ptr == DStream->start) && (DStream->bitsConsumed == (nuint)(sizeof(nuint)) * 8))) ? 1U : 0U);
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/COVER_best_s.cs

@@ -0,0 +1,29 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /**
+     * COVER_best_t is used for two purposes:
+     * 1. Synchronizing threads.
+     * 2. Saving the best parameters and dictionary.
+     *
+     * All of the methods except COVER_best_init() are thread safe if zstd is
+     * compiled with multithreaded support.
+     */
+    public unsafe partial struct COVER_best_s
+    {
+        public int mutex;
+
+        public int cond;
+
+        public nuint liveJobs;
+
+        public void* dict;
+
+        public nuint dictSize;
+
+        public ZDICT_cover_params_t parameters;
+
+        public nuint compressedSize;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/COVER_dictSelection.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /**
+     * Struct used for the dictionary selection function.
+     */
+    public unsafe partial struct COVER_dictSelection
+    {
+        public byte* dictContent;
+
+        public nuint dictSize;
+
+        public nuint totalCompressedSize;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/COVER_epoch_info_t.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /**
+     *Number of epochs and size of each epoch.
+     */
+    public partial struct COVER_epoch_info_t
+    {
+        public uint num;
+
+        public uint size;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/COVER_segment_t.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /**
+     * A segment is a range in the source as well as the score of the segment.
+     */
+    public partial struct COVER_segment_t
+    {
+        public uint begin;
+
+        public uint end;
+
+        public uint score;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/Cover.cs

@@ -0,0 +1,411 @@
+using System;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        public static int g_displayLevel = 2;
+
+        /**
+         * Returns the sum of the sample sizes.
+         */
+        public static nuint COVER_sum(nuint* samplesSizes, uint nbSamples)
+        {
+            nuint sum = 0;
+            uint i;
+
+            for (i = 0; i < nbSamples; ++i)
+            {
+                sum += samplesSizes[i];
+            }
+
+            return sum;
+        }
+
+        /**
+         * Warns the user when their corpus is too small.
+         */
+        public static void COVER_warnOnSmallCorpus(nuint maxDictSize, nuint nbDmers, int displayLevel)
+        {
+            double ratio = (double)(nbDmers) / maxDictSize;
+
+            if (ratio >= 10)
+            {
+                return;
+            }
+
+            if (displayLevel >= 1)
+            {
+        ;
+            }
+
+        }
+
+        /**
+         * Computes the number of epochs and the size of each epoch.
+         * We will make sure that each epoch gets at least 10 * k bytes.
+         *
+         * The COVER algorithms divide the data up into epochs of equal size and
+         * select one segment from each epoch.
+         *
+         * @param maxDictSize The maximum allowed dictionary size.
+         * @param nbDmers     The number of dmers we are training on.
+         * @param k           The parameter k (segment size).
+         * @param passes      The target number of passes over the dmer corpus.
+         *                    More passes means a better dictionary.
+         */
+        public static COVER_epoch_info_t COVER_computeEpochs(uint maxDictSize, uint nbDmers, uint k, uint passes)
+        {
+            uint minEpochSize = k * 10;
+            COVER_epoch_info_t epochs;
+
+            epochs.num = (uint)((1) > (maxDictSize / k / passes) ? (1) : (maxDictSize / k / passes));
+            epochs.size = nbDmers / epochs.num;
+            if (epochs.size >= minEpochSize)
+            {
+                assert(epochs.size * epochs.num <= nbDmers);
+                return epochs;
+            }
+
+            epochs.size = ((minEpochSize) < (nbDmers) ? (minEpochSize) : (nbDmers));
+            epochs.num = nbDmers / epochs.size;
+            assert(epochs.size * epochs.num <= nbDmers);
+            return epochs;
+        }
+
+        /**
+         *  Checks total compressed size of a dictionary
+         */
+        public static nuint COVER_checkTotalCompressedSize(ZDICT_cover_params_t parameters, nuint* samplesSizes, byte* samples, nuint* offsets, nuint nbTrainSamples, nuint nbSamples, byte* dict, nuint dictBufferCapacity)
+        {
+            nuint totalCompressedSize = (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            ZSTD_CCtx_s* cctx;
+            ZSTD_CDict_s* cdict;
+            void* dst;
+            nuint dstCapacity;
+            nuint i;
+
+
+            {
+                nuint maxSampleSize = 0;
+
+                i = parameters.splitPoint < 1.0 ? nbTrainSamples : 0;
+                for (; i < nbSamples; ++i)
+                {
+                    maxSampleSize = ((samplesSizes[i]) > (maxSampleSize) ? (samplesSizes[i]) : (maxSampleSize));
+                }
+
+                dstCapacity = ZSTD_compressBound(maxSampleSize);
+                dst = malloc(dstCapacity);
+            }
+
+            cctx = ZSTD_createCCtx();
+            cdict = ZSTD_createCDict((void*)dict, dictBufferCapacity, parameters.zParams.compressionLevel);
+            if (dst == null || cctx == null || cdict == null)
+            {
+                goto _compressCleanup;
+            }
+
+            totalCompressedSize = dictBufferCapacity;
+            i = parameters.splitPoint < 1.0 ? nbTrainSamples : 0;
+            for (; i < nbSamples; ++i)
+            {
+                nuint size = ZSTD_compress_usingCDict(cctx, dst, dstCapacity, (void*)(samples + offsets[i]), samplesSizes[i], cdict);
+
+                if ((ERR_isError(size)) != 0)
+                {
+                    totalCompressedSize = size;
+                    goto _compressCleanup;
+                }
+
+                totalCompressedSize += size;
+            }
+
+            _compressCleanup:
+            ZSTD_freeCCtx(cctx);
+            ZSTD_freeCDict(cdict);
+            if (dst != null)
+            {
+                free(dst);
+            }
+
+            return totalCompressedSize;
+        }
+
+        /**
+         * Initialize the `COVER_best_t`.
+         */
+        public static void COVER_best_init(COVER_best_s* best)
+        {
+            if (best == null)
+            {
+                return;
+            }
+
+
+
+            best->liveJobs = 0;
+            best->dict = null;
+            best->dictSize = 0;
+            best->compressedSize = unchecked((nuint)(-1));
+            memset((void*)&best->parameters, 0, (nuint)(sizeof(ZDICT_cover_params_t)));
+        }
+
+        /**
+         * Wait until liveJobs == 0.
+         */
+        public static void COVER_best_wait(COVER_best_s* best)
+        {
+            if (best == null)
+            {
+                return;
+            }
+
+
+            while (best->liveJobs != 0)
+            {
+
+            }
+
+
+        }
+
+        /**
+         * Call COVER_best_wait() and then destroy the COVER_best_t.
+         */
+        public static void COVER_best_destroy(COVER_best_s* best)
+        {
+            if (best == null)
+            {
+                return;
+            }
+
+            COVER_best_wait(best);
+            if (best->dict != null)
+            {
+                free(best->dict);
+            }
+
+
+
+        }
+
+        /**
+         * Called when a thread is about to be launched.
+         * Increments liveJobs.
+         */
+        public static void COVER_best_start(COVER_best_s* best)
+        {
+            if (best == null)
+            {
+                return;
+            }
+
+
+            ++best->liveJobs;
+
+        }
+
+        /**
+         * Called when a thread finishes executing, both on error or success.
+         * Decrements liveJobs and signals any waiting threads if liveJobs == 0.
+         * If this dictionary is the best so far save it and its parameters.
+         */
+        public static void COVER_best_finish(COVER_best_s* best, ZDICT_cover_params_t parameters, COVER_dictSelection selection)
+        {
+            void* dict = (void*)selection.dictContent;
+            nuint compressedSize = selection.totalCompressedSize;
+            nuint dictSize = selection.dictSize;
+
+            if (best == null)
+            {
+                return;
+            }
+
+
+            {
+                nuint liveJobs;
+
+
+                --best->liveJobs;
+                liveJobs = best->liveJobs;
+                if (compressedSize < best->compressedSize)
+                {
+                    if (best->dict == null || best->dictSize < dictSize)
+                    {
+                        if (best->dict != null)
+                        {
+                            free(best->dict);
+                        }
+
+                        best->dict = malloc(dictSize);
+                        if (best->dict == null)
+                        {
+                            best->compressedSize = (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+                            best->dictSize = 0;
+
+
+                            return;
+                        }
+                    }
+
+                    if (dict != null)
+                    {
+                        memcpy(best->dict, dict, dictSize);
+                        best->dictSize = dictSize;
+                        best->parameters = parameters;
+                        best->compressedSize = compressedSize;
+                    }
+                }
+
+                if (liveJobs == 0)
+                {
+
+                }
+
+
+            }
+        }
+
+        /**
+          * Error function for COVER_selectDict function. Returns a struct where
+          * return.totalCompressedSize is a ZSTD error.
+          */
+        public static COVER_dictSelection COVER_dictSelectionError(nuint error)
+        {
+            COVER_dictSelection selection = new COVER_dictSelection
+            {
+                dictContent = null,
+                dictSize = 0,
+                totalCompressedSize = error,
+            };
+
+            return selection;
+        }
+
+        /**
+         * Error function for COVER_selectDict function. Checks if the return
+         * value is an error.
+         */
+        public static uint COVER_dictSelectionIsError(COVER_dictSelection selection)
+        {
+            return ((((ERR_isError(selection.totalCompressedSize)) != 0 || selection.dictContent == null)) ? 1U : 0U);
+        }
+
+        /**
+         * Always call after selectDict is called to free up used memory from
+         * newly created dictionary.
+         */
+        public static void COVER_dictSelectionFree(COVER_dictSelection selection)
+        {
+            free((void*)selection.dictContent);
+        }
+
+        /**
+         * Called to finalize the dictionary and select one based on whether or not
+         * the shrink-dict flag was enabled. If enabled the dictionary used is the
+         * smallest dictionary within a specified regression of the compressed size
+         * from the largest dictionary.
+         */
+        public static COVER_dictSelection COVER_selectDict(byte* customDictContent, nuint dictBufferCapacity, nuint dictContentSize, byte* samplesBuffer, nuint* samplesSizes, uint nbFinalizeSamples, nuint nbCheckSamples, nuint nbSamples, ZDICT_cover_params_t @params, nuint* offsets, nuint totalCompressedSize)
+        {
+            nuint largestDict = 0;
+            nuint largestCompressed = 0;
+            byte* customDictContentEnd = customDictContent + dictContentSize;
+            byte* largestDictbuffer = (byte*)(malloc(dictBufferCapacity));
+            byte* candidateDictBuffer = (byte*)(malloc(dictBufferCapacity));
+            double regressionTolerance = ((double)(@params.shrinkDictMaxRegression) / 100.0) + 1.00;
+
+            if (largestDictbuffer == null || candidateDictBuffer == null)
+            {
+                free((void*)largestDictbuffer);
+                free((void*)candidateDictBuffer);
+                return COVER_dictSelectionError(dictContentSize);
+            }
+
+            memcpy((void*)largestDictbuffer, (void*)customDictContent, dictContentSize);
+            dictContentSize = ZDICT_finalizeDictionary((void*)largestDictbuffer, dictBufferCapacity, (void*)customDictContent, dictContentSize, (void*)samplesBuffer, samplesSizes, nbFinalizeSamples, @params.zParams);
+            if ((ZDICT_isError(dictContentSize)) != 0)
+            {
+                free((void*)largestDictbuffer);
+                free((void*)candidateDictBuffer);
+                return COVER_dictSelectionError(dictContentSize);
+            }
+
+            totalCompressedSize = COVER_checkTotalCompressedSize(@params, samplesSizes, samplesBuffer, offsets, nbCheckSamples, nbSamples, largestDictbuffer, dictContentSize);
+            if ((ERR_isError(totalCompressedSize)) != 0)
+            {
+                free((void*)largestDictbuffer);
+                free((void*)candidateDictBuffer);
+                return COVER_dictSelectionError(totalCompressedSize);
+            }
+
+            if (@params.shrinkDict == 0)
+            {
+                COVER_dictSelection selection = new COVER_dictSelection
+                {
+                    dictContent = largestDictbuffer,
+                    dictSize = dictContentSize,
+                    totalCompressedSize = totalCompressedSize,
+                };
+
+                free((void*)candidateDictBuffer);
+                return selection;
+            }
+
+            largestDict = dictContentSize;
+            largestCompressed = totalCompressedSize;
+            dictContentSize = 256;
+            while (dictContentSize < largestDict)
+            {
+                memcpy((void*)candidateDictBuffer, (void*)largestDictbuffer, largestDict);
+                dictContentSize = ZDICT_finalizeDictionary((void*)candidateDictBuffer, dictBufferCapacity, (void*)(customDictContentEnd - dictContentSize), dictContentSize, (void*)samplesBuffer, samplesSizes, nbFinalizeSamples, @params.zParams);
+                if ((ZDICT_isError(dictContentSize)) != 0)
+                {
+                    free((void*)largestDictbuffer);
+                    free((void*)candidateDictBuffer);
+                    return COVER_dictSelectionError(dictContentSize);
+                }
+
+                totalCompressedSize = COVER_checkTotalCompressedSize(@params, samplesSizes, samplesBuffer, offsets, nbCheckSamples, nbSamples, candidateDictBuffer, dictContentSize);
+                if ((ERR_isError(totalCompressedSize)) != 0)
+                {
+                    free((void*)largestDictbuffer);
+                    free((void*)candidateDictBuffer);
+                    return COVER_dictSelectionError(totalCompressedSize);
+                }
+
+                if (totalCompressedSize <= largestCompressed * regressionTolerance)
+                {
+                    COVER_dictSelection selection = new COVER_dictSelection
+                    {
+                        dictContent = candidateDictBuffer,
+                        dictSize = dictContentSize,
+                        totalCompressedSize = totalCompressedSize,
+                    };
+
+                    free((void*)largestDictbuffer);
+                    return selection;
+                }
+
+                dictContentSize *= 2;
+            }
+
+            dictContentSize = largestDict;
+            totalCompressedSize = largestCompressed;
+
+            {
+                COVER_dictSelection selection = new COVER_dictSelection
+                {
+                    dictContent = largestDictbuffer,
+                    dictSize = dictContentSize,
+                    totalCompressedSize = totalCompressedSize,
+                };
+
+                free((void*)candidateDictBuffer);
+                return selection;
+            }
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/DTableDesc.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /*-***************************/
+    /*  generic DTableDesc       */
+    /*-***************************/
+    public partial struct DTableDesc
+    {
+        public byte maxTableLog;
+
+        public byte tableType;
+
+        public byte tableLog;
+
+        public byte reserved;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/EStats_ress_t.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public unsafe partial struct EStats_ress_t
+    {
+        /* dictionary */
+        public ZSTD_CDict_s* dict;
+
+        /* working context */
+        public ZSTD_CCtx_s* zc;
+
+        /* must be ZSTD_BLOCKSIZE_MAX allocated */
+        public void* workPlace;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/EntropyCommon.cs

@@ -0,0 +1,425 @@
+using System;
+using System.Numerics;
+using System.Runtime.CompilerServices;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        /*===   Version   ===*/
+        public static uint FSE_versionNumber()
+        {
+            return (uint)((0 * 100 * 100 + 9 * 100 + 0));
+        }
+
+        /*===   Error Management   ===*/
+        public static uint FSE_isError(nuint code)
+        {
+            return ERR_isError(code);
+        }
+
+        public static string FSE_getErrorName(nuint code)
+        {
+            return ERR_getErrorName(code);
+        }
+
+        /* Error Management */
+        public static uint HUF_isError(nuint code)
+        {
+            return ERR_isError(code);
+        }
+
+        public static string HUF_getErrorName(nuint code)
+        {
+            return ERR_getErrorName(code);
+        }
+
+        /*-**************************************************************
+        *  FSE NCount encoding-decoding
+        ****************************************************************/
+        [InlineMethod.Inline]
+        private static uint FSE_ctz(uint val)
+        {
+            assert(val != 0);
+
+            {
+                return (uint) BitOperations.TrailingZeroCount(val);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint FSE_readNCount_body(short* normalizedCounter, uint* maxSVPtr, uint* tableLogPtr, void* headerBuffer, nuint hbSize)
+        {
+            byte* istart = (byte*)(headerBuffer);
+            byte* iend = istart + hbSize;
+            byte* ip = istart;
+            int nbBits;
+            int remaining;
+            int threshold;
+            uint bitStream;
+            int bitCount;
+            uint charnum = 0;
+            uint maxSV1 = *maxSVPtr + 1;
+            int previous0 = 0;
+
+            if (hbSize < 8)
+            {
+                sbyte* buffer = stackalloc sbyte[8];
+                memset(buffer, 0, sizeof(sbyte) * 8);
+
+                memcpy((void*)(buffer), (headerBuffer), (hbSize));
+
+                {
+                    nuint countSize = FSE_readNCount(normalizedCounter, maxSVPtr, tableLogPtr, (void*)buffer, (nuint)(8));
+
+                    if ((FSE_isError(countSize)) != 0)
+                    {
+                        return countSize;
+                    }
+
+                    if (countSize > hbSize)
+                    {
+                        return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+                    }
+
+                    return countSize;
+                }
+            }
+
+            assert(hbSize >= 8);
+            memset((void*)(normalizedCounter), (0), ((*maxSVPtr + 1) * (nuint)(sizeof(short))));
+            bitStream = MEM_readLE32((void*)ip);
+            nbBits = (int)((bitStream & 0xF) + 5);
+            if (nbBits > 15)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+            }
+
+            bitStream >>= 4;
+            bitCount = 4;
+            *tableLogPtr = (uint)nbBits;
+            remaining = (1 << nbBits) + 1;
+            threshold = 1 << nbBits;
+            nbBits++;
+            for (;;)
+            {
+                if (previous0 != 0)
+                {
+                    int repeats = (int)(FSE_ctz(~bitStream | 0x80000000) >> 1);
+
+                    while (repeats >= 12)
+                    {
+                        charnum += (uint)(3 * 12);
+                        if ((ip <= iend - 7))
+                        {
+                            ip += 3;
+                        }
+                        else
+                        {
+                            bitCount -= (int)(8 * (iend - 7 - ip));
+                            bitCount &= 31;
+                            ip = iend - 4;
+                        }
+
+                        bitStream = MEM_readLE32((void*)ip) >> bitCount;
+                        repeats = (int)(FSE_ctz(~bitStream | 0x80000000) >> 1);
+                    }
+
+                    charnum += (uint)(3 * repeats);
+                    bitStream >>= 2 * repeats;
+                    bitCount += 2 * repeats;
+                    assert((bitStream & 3) < 3);
+                    charnum += bitStream & 3;
+                    bitCount += 2;
+                    if (charnum >= maxSV1)
+                    {
+                        break;
+                    }
+
+                    if ((ip <= iend - 7) || (ip + (bitCount >> 3) <= iend - 4))
+                    {
+                        assert((bitCount >> 3) <= 3);
+                        ip += bitCount >> 3;
+                        bitCount &= 7;
+                    }
+                    else
+                    {
+                        bitCount -= (int)(8 * (iend - 4 - ip));
+                        bitCount &= 31;
+                        ip = iend - 4;
+                    }
+
+                    bitStream = MEM_readLE32((void*)ip) >> bitCount;
+                }
+
+
+                {
+                    int max = (2 * threshold - 1) - remaining;
+                    int count;
+
+                    if ((bitStream & (uint)((threshold - 1))) < (uint)(max))
+                    {
+                        count = (int)(bitStream & (uint)((threshold - 1)));
+                        bitCount += nbBits - 1;
+                    }
+                    else
+                    {
+                        count = (int)(bitStream & (uint)((2 * threshold - 1)));
+                        if (count >= threshold)
+                        {
+                            count -= max;
+                        }
+
+                        bitCount += nbBits;
+                    }
+
+                    count--;
+                    if (count >= 0)
+                    {
+                        remaining -= count;
+                    }
+                    else
+                    {
+                        assert(count == -1);
+                        remaining += count;
+                    }
+
+                    normalizedCounter[charnum++] = (short)(count);
+                    previous0 = (count == 0 ? 1 : 0);
+                    assert(threshold > 1);
+                    if (remaining < threshold)
+                    {
+                        if (remaining <= 1)
+                        {
+                            break;
+                        }
+
+                        nbBits = (int)(BIT_highbit32((uint)remaining) + 1);
+                        threshold = 1 << (nbBits - 1);
+                    }
+
+                    if (charnum >= maxSV1)
+                    {
+                        break;
+                    }
+
+                    if ((ip <= iend - 7) || (ip + (bitCount >> 3) <= iend - 4))
+                    {
+                        ip += bitCount >> 3;
+                        bitCount &= 7;
+                    }
+                    else
+                    {
+                        bitCount -= (int)(8 * (iend - 4 - ip));
+                        bitCount &= 31;
+                        ip = iend - 4;
+                    }
+
+                    bitStream = MEM_readLE32((void*)ip) >> bitCount;
+                }
+            }
+
+            if (remaining != 1)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+            }
+
+            if (charnum > maxSV1)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_maxSymbolValue_tooSmall)));
+            }
+
+            if (bitCount > 32)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+            }
+
+            *maxSVPtr = charnum - 1;
+            ip += (bitCount + 7) >> 3;
+            return (nuint)(ip - istart);
+        }
+
+        /* Avoids the FORCE_INLINE of the _body() function. */
+        private static nuint FSE_readNCount_body_default(short* normalizedCounter, uint* maxSVPtr, uint* tableLogPtr, void* headerBuffer, nuint hbSize)
+        {
+            return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
+        }
+
+        private static nuint FSE_readNCount_body_bmi2(short* normalizedCounter, uint* maxSVPtr, uint* tableLogPtr, void* headerBuffer, nuint hbSize)
+        {
+            return FSE_readNCount_body(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
+        }
+
+        /*! FSE_readNCount_bmi2():
+         * Same as FSE_readNCount() but pass bmi2=1 when your CPU supports BMI2 and 0 otherwise.
+         */
+        public static nuint FSE_readNCount_bmi2(short* normalizedCounter, uint* maxSVPtr, uint* tableLogPtr, void* headerBuffer, nuint hbSize, int bmi2)
+        {
+            if (bmi2 != 0)
+            {
+                return FSE_readNCount_body_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
+            }
+
+            return FSE_readNCount_body_default(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
+        }
+
+        /*! FSE_readNCount():
+            Read compactly saved 'normalizedCounter' from 'rBuffer'.
+            @return : size read from 'rBuffer',
+                      or an errorCode, which can be tested using FSE_isError().
+                      maxSymbolValuePtr[0] and tableLogPtr[0] will also be updated with their respective values */
+        public static nuint FSE_readNCount(short* normalizedCounter, uint* maxSVPtr, uint* tableLogPtr, void* headerBuffer, nuint hbSize)
+        {
+            return FSE_readNCount_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize, 0);
+        }
+
+        /*! HUF_readStats() :
+            Read compact Huffman tree, saved by HUF_writeCTable().
+            `huffWeight` is destination buffer.
+            `rankStats` is assumed to be a table of at least HUF_TABLELOG_MAX U32.
+            @return : size read from `src` , or an error Code .
+            Note : Needed by HUF_readCTable() and HUF_readDTableX?() .
+        */
+        public static nuint HUF_readStats(byte* huffWeight, nuint hwSize, uint* rankStats, uint* nbSymbolsPtr, uint* tableLogPtr, void* src, nuint srcSize)
+        {
+            uint* wksp = stackalloc uint[218];
+
+            return HUF_readStats_wksp(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, (void*)wksp, (nuint)(sizeof(uint) * 218), 0);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint HUF_readStats_body(byte* huffWeight, nuint hwSize, uint* rankStats, uint* nbSymbolsPtr, uint* tableLogPtr, void* src, nuint srcSize, void* workSpace, nuint wkspSize, int bmi2)
+        {
+            uint weightTotal;
+            byte* ip = (byte*)(src);
+            nuint iSize;
+            nuint oSize;
+
+            if (srcSize == 0)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+            }
+
+            iSize = ip[0];
+            if (iSize >= 128)
+            {
+                oSize = iSize - 127;
+                iSize = ((oSize + 1) / 2);
+                if (iSize + 1 > srcSize)
+                {
+                    return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+                }
+
+                if (oSize >= hwSize)
+                {
+                    return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+                }
+
+                ip += 1;
+
+                {
+                    uint n;
+
+                    for (n = 0; n < oSize; n += 2)
+                    {
+                        huffWeight[n] = (byte)(ip[n / 2] >> 4);
+                        huffWeight[n + 1] = (byte)(ip[n / 2] & 15);
+                    }
+                }
+            }
+            else
+            {
+                if (iSize + 1 > srcSize)
+                {
+                    return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+                }
+
+                oSize = FSE_decompress_wksp_bmi2((void*)huffWeight, hwSize - 1, (void*)(ip + 1), iSize, 6, workSpace, wkspSize, bmi2);
+                if ((FSE_isError(oSize)) != 0)
+                {
+                    return oSize;
+                }
+            }
+
+            memset((void*)(rankStats), (0), ((uint)((12 + 1)) * (nuint)(sizeof(uint))));
+            weightTotal = 0;
+
+            {
+                uint n;
+
+                for (n = 0; n < oSize; n++)
+                {
+                    if (huffWeight[n] >= 12)
+                    {
+                        return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+                    }
+
+                    rankStats[huffWeight[n]]++;
+                    weightTotal += (uint)((1 << (int)(huffWeight[n])) >> 1);
+                }
+            }
+
+            if (weightTotal == 0)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+            }
+
+
+            {
+                uint tableLog = BIT_highbit32(weightTotal) + 1;
+
+                if (tableLog > 12)
+                {
+                    return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+                }
+
+                *tableLogPtr = tableLog;
+
+                {
+                    uint total = (uint)(1 << (int)tableLog);
+                    uint rest = total - weightTotal;
+                    uint verif = (uint)(1 << (int)(BIT_highbit32(rest)));
+                    uint lastWeight = BIT_highbit32(rest) + 1;
+
+                    if (verif != rest)
+                    {
+                        return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+                    }
+
+                    huffWeight[oSize] = (byte)(lastWeight);
+                    rankStats[lastWeight]++;
+                }
+            }
+
+            if ((rankStats[1] < 2) || (rankStats[1] & 1) != 0)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_corruption_detected)));
+            }
+
+            *nbSymbolsPtr = (uint)(oSize + 1);
+            return iSize + 1;
+        }
+
+        /* Avoids the FORCE_INLINE of the _body() function. */
+        private static nuint HUF_readStats_body_default(byte* huffWeight, nuint hwSize, uint* rankStats, uint* nbSymbolsPtr, uint* tableLogPtr, void* src, nuint srcSize, void* workSpace, nuint wkspSize)
+        {
+            return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 0);
+        }
+
+        private static nuint HUF_readStats_body_bmi2(byte* huffWeight, nuint hwSize, uint* rankStats, uint* nbSymbolsPtr, uint* tableLogPtr, void* src, nuint srcSize, void* workSpace, nuint wkspSize)
+        {
+            return HUF_readStats_body(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize, 1);
+        }
+
+        public static nuint HUF_readStats_wksp(byte* huffWeight, nuint hwSize, uint* rankStats, uint* nbSymbolsPtr, uint* tableLogPtr, void* src, nuint srcSize, void* workSpace, nuint wkspSize, int bmi2)
+        {
+            if (bmi2 != 0)
+            {
+                return HUF_readStats_body_bmi2(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
+            }
+
+            return HUF_readStats_body_default(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/ErrorPrivate.cs

@@ -0,0 +1,184 @@
+using System;
+using System.Runtime.CompilerServices;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint ERR_isError(nuint code)
+        {
+            return (((code > (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_maxCode))))) ? 1U : 0U);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static ZSTD_ErrorCode ERR_getErrorCode(nuint code)
+        {
+            if ((ERR_isError(code)) == 0)
+            {
+                return (ZSTD_ErrorCode)(0);
+            }
+
+            return (ZSTD_ErrorCode)(0 - code);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static string ERR_getErrorName(nuint code)
+        {
+            return ERR_getErrorString(ERR_getErrorCode(code));
+        }
+
+        /*-****************************************
+        *  Error Strings
+        ******************************************/
+        public static string ERR_getErrorString(ZSTD_ErrorCode code)
+        {
+            var notErrorCode = "Unspecified error code";
+
+            switch (code)
+            {
+                case ZSTD_ErrorCode.ZSTD_error_no_error:
+                {
+                    return "No error detected";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_GENERIC:
+                {
+                    return "Error (generic)";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_prefix_unknown:
+                {
+                    return "Unknown frame descriptor";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_version_unsupported:
+                {
+                    return "Version not supported";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_frameParameter_unsupported:
+                {
+                    return "Unsupported frame parameter";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_frameParameter_windowTooLarge:
+                {
+                    return "Frame requires too much memory for decoding";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_corruption_detected:
+                {
+                    return "Corrupted block detected";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_checksum_wrong:
+                {
+                    return "Restored data doesn't match checksum";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_parameter_unsupported:
+                {
+                    return "Unsupported parameter";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_parameter_outOfBound:
+                {
+                    return "Parameter is out of bound";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_init_missing:
+                {
+                    return "Context should be init first";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_memory_allocation:
+                {
+                    return "Allocation error : not enough memory";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_workSpace_tooSmall:
+                {
+                    return "workSpace buffer is not large enough";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_stage_wrong:
+                {
+                    return "Operation not authorized at current processing stage";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge:
+                {
+                    return "tableLog requires too much memory : unsupported";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_maxSymbolValue_tooLarge:
+                {
+                    return "Unsupported max Symbol Value : too large";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_maxSymbolValue_tooSmall:
+                {
+                    return "Specified maxSymbolValue is too small";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_dictionary_corrupted:
+                {
+                    return "Dictionary is corrupted";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_dictionary_wrong:
+                {
+                    return "Dictionary mismatch";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_dictionaryCreation_failed:
+                {
+                    return "Cannot create Dictionary from provided samples";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall:
+                {
+                    return "Destination buffer is too small";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_srcSize_wrong:
+                {
+                    return "Src size is incorrect";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_dstBuffer_null:
+                {
+                    return "Operation on NULL destination buffer";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_frameIndex_tooLarge:
+                {
+                    return "Frame index is too large";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_seekableIO:
+                {
+                    return "An I/O error occurred when reading/seeking";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_dstBuffer_wrong:
+                {
+                    return "Destination buffer is wrong";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_srcBuffer_wrong:
+                {
+                    return "Source buffer is wrong";
+                }
+
+                case ZSTD_ErrorCode.ZSTD_error_maxCode:
+                default:
+                {
+                    return notErrorCode;
+                }
+            }
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FASTCOVER_accel_t.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /*-*************************************
+    * Acceleration
+    ***************************************/
+    public partial struct FASTCOVER_accel_t
+    {
+        /* Percentage of training samples used for ZDICT_finalizeDictionary */
+        public uint finalize;
+
+        /* Number of dmer skipped between each dmer counted in computeFrequency */
+        public uint skip;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FASTCOVER_ctx_t.cs

@@ -0,0 +1,32 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /*-*************************************
+    * Context
+    ***************************************/
+    public unsafe partial struct FASTCOVER_ctx_t
+    {
+        public byte* samples;
+
+        public nuint* offsets;
+
+        public nuint* samplesSizes;
+
+        public nuint nbSamples;
+
+        public nuint nbTrainSamples;
+
+        public nuint nbTestSamples;
+
+        public nuint nbDmers;
+
+        public uint* freqs;
+
+        public uint d;
+
+        public uint f;
+
+        public FASTCOVER_accel_t accelParams;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FASTCOVER_tryParameters_data_s.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /**
+     * Parameters for FASTCOVER_tryParameters().
+     */
+    public unsafe partial struct FASTCOVER_tryParameters_data_s
+    {
+        public FASTCOVER_ctx_t* ctx;
+
+        public COVER_best_s* best;
+
+        public nuint dictBufferCapacity;
+
+        public ZDICT_cover_params_t parameters;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FSE_CState_t.cs

@@ -0,0 +1,22 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /* *****************************************
+    *  FSE symbol compression API
+    *******************************************/
+    /*!
+       This API consists of small unitary functions, which highly benefit from being inlined.
+       Hence their body are included in next section.
+    */
+    public unsafe partial struct FSE_CState_t
+    {
+        public nint value;
+
+        public void* stateTable;
+
+        public void* symbolTT;
+
+        public uint stateLog;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FSE_DState_t.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /* *****************************************
+    *  FSE symbol decompression API
+    *******************************************/
+    public unsafe partial struct FSE_DState_t
+    {
+        public nuint state;
+
+        /* precise table may vary, depending on U16 */
+        public void* table;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FSE_DTableHeader.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /* ======    Decompression    ====== */
+    public partial struct FSE_DTableHeader
+    {
+        public ushort tableLog;
+
+        public ushort fastMode;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FSE_DecompressWksp.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public unsafe partial struct FSE_DecompressWksp
+    {
+        public fixed short ncount[256];
+
+        /* Dynamically sized */
+        public fixed uint dtable[1];
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FSE_decode_t.cs

@@ -0,0 +1,13 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public partial struct FSE_decode_t
+    {
+        public ushort newState;
+
+        public byte symbol;
+
+        public byte nbBits;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FSE_repeat.cs

@@ -0,0 +1,11 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public enum FSE_repeat
+    {
+        FSE_repeat_none,
+        FSE_repeat_check,
+        FSE_repeat_valid,
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FSE_symbolCompressionTransform.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /* *****************************************
+    *  Implementation of inlined functions
+    *******************************************/
+    public partial struct FSE_symbolCompressionTransform
+    {
+        public int deltaFindState;
+
+        public uint deltaNbBits;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/Fastcover.cs

@@ -0,0 +1,715 @@
+using System;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        /*-*************************************
+        * Hash Functions
+        ***************************************/
+        /**
+         * Hash the d-byte value pointed to by p and mod 2^f into the frequency vector
+         */
+        private static nuint FASTCOVER_hashPtrToIndex(void* p, uint f, uint d)
+        {
+            if (d == 6)
+            {
+                return ZSTD_hash6Ptr(p, f);
+            }
+
+            return ZSTD_hash8Ptr(p, f);
+        }
+
+        public static FASTCOVER_accel_t* FASTCOVER_defaultAccelParameters = GetArrayPointer(new FASTCOVER_accel_t[11]
+        {
+            new FASTCOVER_accel_t
+            {
+                finalize = 100,
+                skip = 0,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 100,
+                skip = 0,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 50,
+                skip = 1,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 34,
+                skip = 2,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 25,
+                skip = 3,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 20,
+                skip = 4,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 17,
+                skip = 5,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 14,
+                skip = 6,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 13,
+                skip = 7,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 11,
+                skip = 8,
+            },
+            new FASTCOVER_accel_t
+            {
+                finalize = 10,
+                skip = 9,
+            },
+        });
+
+        /*-*************************************
+        *  Helper functions
+        ***************************************/
+        /**
+         * Selects the best segment in an epoch.
+         * Segments of are scored according to the function:
+         *
+         * Let F(d) be the frequency of all dmers with hash value d.
+         * Let S_i be hash value of the dmer at position i of segment S which has length k.
+         *
+         *     Score(S) = F(S_1) + F(S_2) + ... + F(S_{k-d+1})
+         *
+         * Once the dmer with hash value d is in the dictionary we set F(d) = 0.
+         */
+        private static COVER_segment_t FASTCOVER_selectSegment(FASTCOVER_ctx_t* ctx, uint* freqs, uint begin, uint end, ZDICT_cover_params_t parameters, ushort* segmentFreqs)
+        {
+            uint k = parameters.k;
+            uint d = parameters.d;
+            uint f = ctx->f;
+            uint dmersInK = k - d + 1;
+            COVER_segment_t bestSegment = new COVER_segment_t
+            {
+                begin = 0,
+                end = 0,
+                score = 0,
+            };
+            COVER_segment_t activeSegment;
+
+            activeSegment.begin = begin;
+            activeSegment.end = begin;
+            activeSegment.score = 0;
+            while (activeSegment.end < end)
+            {
+                nuint idx = FASTCOVER_hashPtrToIndex((void*)(ctx->samples + activeSegment.end), f, d);
+
+                if (segmentFreqs[idx] == 0)
+                {
+                    activeSegment.score += freqs[idx];
+                }
+
+                activeSegment.end += 1;
+                segmentFreqs[idx] += 1;
+                if (activeSegment.end - activeSegment.begin == dmersInK + 1)
+                {
+                    nuint delIndex = FASTCOVER_hashPtrToIndex((void*)(ctx->samples + activeSegment.begin), f, d);
+
+                    segmentFreqs[delIndex] -= 1;
+                    if (segmentFreqs[delIndex] == 0)
+                    {
+                        activeSegment.score -= freqs[delIndex];
+                    }
+
+                    activeSegment.begin += 1;
+                }
+
+                if (activeSegment.score > bestSegment.score)
+                {
+                    bestSegment = activeSegment;
+                }
+            }
+
+            while (activeSegment.begin < end)
+            {
+                nuint delIndex = FASTCOVER_hashPtrToIndex((void*)(ctx->samples + activeSegment.begin), f, d);
+
+                segmentFreqs[delIndex] -= 1;
+                activeSegment.begin += 1;
+            }
+
+
+            {
+                uint pos;
+
+                for (pos = bestSegment.begin; pos != bestSegment.end; ++pos)
+                {
+                    nuint i = FASTCOVER_hashPtrToIndex((void*)(ctx->samples + pos), f, d);
+
+                    freqs[i] = 0;
+                }
+            }
+
+            return bestSegment;
+        }
+
+        private static int FASTCOVER_checkParameters(ZDICT_cover_params_t parameters, nuint maxDictSize, uint f, uint accel)
+        {
+            if (parameters.d == 0 || parameters.k == 0)
+            {
+                return 0;
+            }
+
+            if (parameters.d != 6 && parameters.d != 8)
+            {
+                return 0;
+            }
+
+            if (parameters.k > maxDictSize)
+            {
+                return 0;
+            }
+
+            if (parameters.d > parameters.k)
+            {
+                return 0;
+            }
+
+            if (f > 31 || f == 0)
+            {
+                return 0;
+            }
+
+            if (parameters.splitPoint <= 0 || parameters.splitPoint > 1)
+            {
+                return 0;
+            }
+
+            if (accel > 10 || accel == 0)
+            {
+                return 0;
+            }
+
+            return 1;
+        }
+
+        /**
+         * Clean up a context initialized with `FASTCOVER_ctx_init()`.
+         */
+        private static void FASTCOVER_ctx_destroy(FASTCOVER_ctx_t* ctx)
+        {
+            if (ctx == null)
+            {
+                return;
+            }
+
+            free((void*)ctx->freqs);
+            ctx->freqs = null;
+            free((void*)ctx->offsets);
+            ctx->offsets = null;
+        }
+
+        /**
+         * Calculate for frequency of hash value of each dmer in ctx->samples
+         */
+        private static void FASTCOVER_computeFrequency(uint* freqs, FASTCOVER_ctx_t* ctx)
+        {
+            uint f = ctx->f;
+            uint d = ctx->d;
+            uint skip = ctx->accelParams.skip;
+            uint readLength = ((d) > (8) ? (d) : (8));
+            nuint i;
+
+            assert(ctx->nbTrainSamples >= 5);
+            assert(ctx->nbTrainSamples <= ctx->nbSamples);
+            for (i = 0; i < ctx->nbTrainSamples; i++)
+            {
+                nuint start = ctx->offsets[i];
+                nuint currSampleEnd = ctx->offsets[i + 1];
+
+                while (start + readLength <= currSampleEnd)
+                {
+                    nuint dmerIndex = FASTCOVER_hashPtrToIndex((void*)(ctx->samples + start), f, d);
+
+                    freqs[dmerIndex]++;
+                    start = start + skip + 1;
+                }
+            }
+        }
+
+        /**
+         * Prepare a context for dictionary building.
+         * The context is only dependent on the parameter `d` and can used multiple
+         * times.
+         * Returns 0 on success or error code on error.
+         * The context must be destroyed with `FASTCOVER_ctx_destroy()`.
+         */
+        private static nuint FASTCOVER_ctx_init(FASTCOVER_ctx_t* ctx, void* samplesBuffer, nuint* samplesSizes, uint nbSamples, uint d, double splitPoint, uint f, FASTCOVER_accel_t accelParams)
+        {
+            byte* samples = (byte*)(samplesBuffer);
+            nuint totalSamplesSize = COVER_sum(samplesSizes, nbSamples);
+            uint nbTrainSamples = splitPoint < 1.0 ? (uint)((double)(nbSamples) * splitPoint) : nbSamples;
+            uint nbTestSamples = splitPoint < 1.0 ? nbSamples - nbTrainSamples : nbSamples;
+            nuint trainingSamplesSize = splitPoint < 1.0 ? COVER_sum(samplesSizes, nbTrainSamples) : totalSamplesSize;
+            nuint testSamplesSize = splitPoint < 1.0 ? COVER_sum(samplesSizes + nbTrainSamples, nbTestSamples) : totalSamplesSize;
+
+            if (totalSamplesSize < ((d) > ((nuint)(sizeof(ulong))) ? (d) : ((nuint)(sizeof(ulong)))) || totalSamplesSize >= (nuint)((nuint)(sizeof(nuint)) == 8 ? (unchecked((uint)(-1))) : ((uint)(1) * (1U << 30))))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+            }
+
+            if (nbTrainSamples < 5)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+            }
+
+            if (nbTestSamples < 1)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+            }
+
+            memset((void*)ctx, 0, (nuint)(sizeof(FASTCOVER_ctx_t)));
+            ctx->samples = samples;
+            ctx->samplesSizes = samplesSizes;
+            ctx->nbSamples = nbSamples;
+            ctx->nbTrainSamples = nbTrainSamples;
+            ctx->nbTestSamples = nbTestSamples;
+            ctx->nbDmers = trainingSamplesSize - ((d) > ((nuint)(sizeof(ulong))) ? (d) : ((nuint)(sizeof(ulong)))) + 1;
+            ctx->d = d;
+            ctx->f = f;
+            ctx->accelParams = accelParams;
+            ctx->offsets = (nuint*)(calloc((nbSamples + 1), (nuint)(sizeof(nuint))));
+            if (ctx->offsets == null)
+            {
+                FASTCOVER_ctx_destroy(ctx);
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_memory_allocation)));
+            }
+
+
+            {
+                uint i;
+
+                ctx->offsets[0] = 0;
+                assert(nbSamples >= 5);
+                for (i = 1; i <= nbSamples; ++i)
+                {
+                    ctx->offsets[i] = ctx->offsets[i - 1] + samplesSizes[i - 1];
+                }
+            }
+
+            ctx->freqs = (uint*)(calloc((nuint)((ulong)(1) << (int)f), (nuint)(sizeof(uint))));
+            if (ctx->freqs == null)
+            {
+                FASTCOVER_ctx_destroy(ctx);
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_memory_allocation)));
+            }
+
+            FASTCOVER_computeFrequency(ctx->freqs, ctx);
+            return 0;
+        }
+
+        /**
+         * Given the prepared context build the dictionary.
+         */
+        private static nuint FASTCOVER_buildDictionary(FASTCOVER_ctx_t* ctx, uint* freqs, void* dictBuffer, nuint dictBufferCapacity, ZDICT_cover_params_t parameters, ushort* segmentFreqs)
+        {
+            byte* dict = (byte*)(dictBuffer);
+            nuint tail = dictBufferCapacity;
+            COVER_epoch_info_t epochs = COVER_computeEpochs((uint)(dictBufferCapacity), (uint)(ctx->nbDmers), parameters.k, 1);
+            nuint maxZeroScoreRun = 10;
+            nuint zeroScoreRun = 0;
+            nuint epoch;
+
+            for (epoch = 0; tail > 0; epoch = (nuint)((epoch + 1) % epochs.num))
+            {
+                uint epochBegin = (uint)(epoch * epochs.size);
+                uint epochEnd = epochBegin + epochs.size;
+                nuint segmentSize;
+                COVER_segment_t segment = FASTCOVER_selectSegment(ctx, freqs, epochBegin, epochEnd, parameters, segmentFreqs);
+
+                if (segment.score == 0)
+                {
+                    if (++zeroScoreRun >= maxZeroScoreRun)
+                    {
+                        break;
+                    }
+
+                    continue;
+                }
+
+                zeroScoreRun = 0;
+                segmentSize = ((segment.end - segment.begin + parameters.d - 1) < (tail) ? (segment.end - segment.begin + parameters.d - 1) : (tail));
+                if (segmentSize < parameters.d)
+                {
+                    break;
+                }
+
+                tail -= segmentSize;
+                memcpy((void*)(dict + tail), (void*)(ctx->samples + segment.begin), segmentSize);
+            }
+
+            return tail;
+        }
+
+        /**
+         * Tries a set of parameters and updates the COVER_best_t with the results.
+         * This function is thread safe if zstd is compiled with multithreaded support.
+         * It takes its parameters as an *OWNING* opaque pointer to support threading.
+         */
+        private static void FASTCOVER_tryParameters(void* opaque)
+        {
+            FASTCOVER_tryParameters_data_s* data = (FASTCOVER_tryParameters_data_s*)(opaque);
+            FASTCOVER_ctx_t* ctx = data->ctx;
+            ZDICT_cover_params_t parameters = data->parameters;
+            nuint dictBufferCapacity = data->dictBufferCapacity;
+            nuint totalCompressedSize = (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            ushort* segmentFreqs = (ushort*)(calloc((nuint)((ulong)(1) << (int)ctx->f), (nuint)(2)));
+            byte* dict = (byte*)(malloc(dictBufferCapacity));
+            COVER_dictSelection selection = COVER_dictSelectionError((unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC))));
+            uint* freqs = (uint*)(malloc((nuint)(((ulong)(1) << (int)ctx->f) * (nuint)(4))));
+
+            if (segmentFreqs == null || dict == null || freqs == null)
+            {
+                goto _cleanup;
+            }
+
+            memcpy((void*)freqs, (void*)ctx->freqs, (nuint)(((ulong)(1) << (int)ctx->f) * (nuint)(sizeof(uint))));
+
+            {
+                nuint tail = FASTCOVER_buildDictionary(ctx, freqs, (void*)dict, dictBufferCapacity, parameters, segmentFreqs);
+                uint nbFinalizeSamples = (uint)(ctx->nbTrainSamples * ctx->accelParams.finalize / 100);
+
+                selection = COVER_selectDict(dict + tail, dictBufferCapacity, dictBufferCapacity - tail, ctx->samples, ctx->samplesSizes, nbFinalizeSamples, ctx->nbTrainSamples, ctx->nbSamples, parameters, ctx->offsets, totalCompressedSize);
+                if ((COVER_dictSelectionIsError(selection)) != 0)
+                {
+                    goto _cleanup;
+                }
+            }
+
+            _cleanup:
+            free((void*)dict);
+            COVER_best_finish(data->best, parameters, selection);
+            free((void*)data);
+            free((void*)segmentFreqs);
+            COVER_dictSelectionFree(selection);
+            free((void*)freqs);
+        }
+
+        private static void FASTCOVER_convertToCoverParams(ZDICT_fastCover_params_t fastCoverParams, ZDICT_cover_params_t* coverParams)
+        {
+            coverParams->k = fastCoverParams.k;
+            coverParams->d = fastCoverParams.d;
+            coverParams->steps = fastCoverParams.steps;
+            coverParams->nbThreads = fastCoverParams.nbThreads;
+            coverParams->splitPoint = fastCoverParams.splitPoint;
+            coverParams->zParams = fastCoverParams.zParams;
+            coverParams->shrinkDict = fastCoverParams.shrinkDict;
+        }
+
+        private static void FASTCOVER_convertToFastCoverParams(ZDICT_cover_params_t coverParams, ZDICT_fastCover_params_t* fastCoverParams, uint f, uint accel)
+        {
+            fastCoverParams->k = coverParams.k;
+            fastCoverParams->d = coverParams.d;
+            fastCoverParams->steps = coverParams.steps;
+            fastCoverParams->nbThreads = coverParams.nbThreads;
+            fastCoverParams->splitPoint = coverParams.splitPoint;
+            fastCoverParams->f = f;
+            fastCoverParams->accel = accel;
+            fastCoverParams->zParams = coverParams.zParams;
+            fastCoverParams->shrinkDict = coverParams.shrinkDict;
+        }
+
+        /*! ZDICT_trainFromBuffer_fastCover():
+         *  Train a dictionary from an array of samples using a modified version of COVER algorithm.
+         *  Samples must be stored concatenated in a single flat buffer `samplesBuffer`,
+         *  supplied with an array of sizes `samplesSizes`, providing the size of each sample, in order.
+         *  d and k are required.
+         *  All other parameters are optional, will use default values if not provided
+         *  The resulting dictionary will be saved into `dictBuffer`.
+         * @return: size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
+         *          or an error code, which can be tested with ZDICT_isError().
+         *          See ZDICT_trainFromBuffer() for details on failure modes.
+         *  Note: ZDICT_trainFromBuffer_fastCover() requires 6 * 2^f bytes of memory.
+         *  Tips: In general, a reasonable dictionary has a size of ~ 100 KB.
+         *        It's possible to select smaller or larger size, just by specifying `dictBufferCapacity`.
+         *        In general, it's recommended to provide a few thousands samples, though this can vary a lot.
+         *        It's recommended that total size of all samples be about ~x100 times the target size of dictionary.
+         */
+        public static nuint ZDICT_trainFromBuffer_fastCover(void* dictBuffer, nuint dictBufferCapacity, void* samplesBuffer, nuint* samplesSizes, uint nbSamples, ZDICT_fastCover_params_t parameters)
+        {
+            byte* dict = (byte*)(dictBuffer);
+            FASTCOVER_ctx_t ctx;
+            ZDICT_cover_params_t coverParams;
+            FASTCOVER_accel_t accelParams;
+
+            g_displayLevel = (int)parameters.zParams.notificationLevel;
+            parameters.splitPoint = 1.0;
+            parameters.f = (uint)(parameters.f == 0 ? 20 : parameters.f);
+            parameters.accel = (uint)(parameters.accel == 0 ? 1 : parameters.accel);
+            memset((void*)&coverParams, 0, (nuint)(sizeof(ZDICT_cover_params_t)));
+            FASTCOVER_convertToCoverParams(parameters, &coverParams);
+            if ((FASTCOVER_checkParameters(coverParams, dictBufferCapacity, parameters.f, parameters.accel)) == 0)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_parameter_outOfBound)));
+            }
+
+            if (nbSamples == 0)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+            }
+
+            if (dictBufferCapacity < 256)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+            }
+
+            accelParams = FASTCOVER_defaultAccelParameters[parameters.accel];
+
+            {
+                nuint initVal = FASTCOVER_ctx_init(&ctx, samplesBuffer, samplesSizes, nbSamples, coverParams.d, parameters.splitPoint, parameters.f, accelParams);
+
+                if ((ERR_isError(initVal)) != 0)
+                {
+                    return initVal;
+                }
+            }
+
+            COVER_warnOnSmallCorpus(dictBufferCapacity, ctx.nbDmers, g_displayLevel);
+
+            {
+                ushort* segmentFreqs = (ushort*)(calloc((nuint)((ulong)(1) << (int)parameters.f), (nuint)(2)));
+                nuint tail = FASTCOVER_buildDictionary(&ctx, ctx.freqs, dictBuffer, dictBufferCapacity, coverParams, segmentFreqs);
+                uint nbFinalizeSamples = (uint)(ctx.nbTrainSamples * ctx.accelParams.finalize / 100);
+                nuint dictionarySize = ZDICT_finalizeDictionary((void*)dict, dictBufferCapacity, (void*)(dict + tail), dictBufferCapacity - tail, samplesBuffer, samplesSizes, nbFinalizeSamples, coverParams.zParams);
+
+                if ((ERR_isError(dictionarySize)) == 0)
+                {
+        ;
+                }
+
+                FASTCOVER_ctx_destroy(&ctx);
+                free((void*)segmentFreqs);
+                return dictionarySize;
+            }
+        }
+
+        /*! ZDICT_optimizeTrainFromBuffer_fastCover():
+         * The same requirements as above hold for all the parameters except `parameters`.
+         * This function tries many parameter combinations (specifically, k and d combinations)
+         * and picks the best parameters. `*parameters` is filled with the best parameters found,
+         * dictionary constructed with those parameters is stored in `dictBuffer`.
+         * All of the parameters d, k, steps, f, and accel are optional.
+         * If d is non-zero then we don't check multiple values of d, otherwise we check d = {6, 8}.
+         * if steps is zero it defaults to its default value.
+         * If k is non-zero then we don't check multiple values of k, otherwise we check steps values in [50, 2000].
+         * If f is zero, default value of 20 is used.
+         * If accel is zero, default value of 1 is used.
+         *
+         * @return: size of dictionary stored into `dictBuffer` (<= `dictBufferCapacity`)
+         *          or an error code, which can be tested with ZDICT_isError().
+         *          On success `*parameters` contains the parameters selected.
+         *          See ZDICT_trainFromBuffer() for details on failure modes.
+         * Note: ZDICT_optimizeTrainFromBuffer_fastCover() requires about 6 * 2^f bytes of memory for each thread.
+         */
+        public static nuint ZDICT_optimizeTrainFromBuffer_fastCover(void* dictBuffer, nuint dictBufferCapacity, void* samplesBuffer, nuint* samplesSizes, uint nbSamples, ZDICT_fastCover_params_t* parameters)
+        {
+            ZDICT_cover_params_t coverParams;
+            FASTCOVER_accel_t accelParams;
+            uint nbThreads = parameters->nbThreads;
+            double splitPoint = parameters->splitPoint <= 0.0 ? 0.75 : parameters->splitPoint;
+            uint kMinD = (uint)(parameters->d == 0 ? 6 : parameters->d);
+            uint kMaxD = (uint)(parameters->d == 0 ? 8 : parameters->d);
+            uint kMinK = (uint)(parameters->k == 0 ? 50 : parameters->k);
+            uint kMaxK = (uint)(parameters->k == 0 ? 2000 : parameters->k);
+            uint kSteps = (uint)(parameters->steps == 0 ? 40 : parameters->steps);
+            uint kStepSize = (((kMaxK - kMinK) / kSteps) > (1) ? ((kMaxK - kMinK) / kSteps) : (1));
+            uint kIterations = (1 + (kMaxD - kMinD) / 2) * (1 + (kMaxK - kMinK) / kStepSize);
+            uint f = (uint)(parameters->f == 0 ? 20 : parameters->f);
+            uint accel = (uint)(parameters->accel == 0 ? 1 : parameters->accel);
+            uint shrinkDict = 0;
+            int displayLevel = (int)parameters->zParams.notificationLevel;
+            uint iteration = 1;
+            uint d;
+            uint k;
+            COVER_best_s best;
+            int warned = 0;
+
+            if (splitPoint <= 0 || splitPoint > 1)
+            {
+                if (displayLevel >= 1)
+                {
+        ;
+                }
+
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_parameter_outOfBound)));
+            }
+
+            if (accel == 0 || accel > 10)
+            {
+                if (displayLevel >= 1)
+                {
+        ;
+                }
+
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_parameter_outOfBound)));
+            }
+
+            if (kMinK < kMaxD || kMaxK < kMinK)
+            {
+                if (displayLevel >= 1)
+                {
+        ;
+                }
+
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_parameter_outOfBound)));
+            }
+
+            if (nbSamples == 0)
+            {
+                if (displayLevel >= 1)
+                {
+        ;
+                }
+
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_srcSize_wrong)));
+            }
+
+            if (dictBufferCapacity < 256)
+            {
+                if (displayLevel >= 1)
+                {
+        ;
+                }
+
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+            }
+
+            if (nbThreads > 1)
+            {
+                throw new NotImplementedException("Multiple threads are not supported");
+            }
+
+            COVER_best_init(&best);
+            memset((void*)&coverParams, 0, (nuint)(sizeof(ZDICT_cover_params_t)));
+            FASTCOVER_convertToCoverParams(*parameters, &coverParams);
+            accelParams = FASTCOVER_defaultAccelParameters[accel];
+            g_displayLevel = displayLevel == 0 ? 0 : displayLevel - 1;
+            if (displayLevel >= 2)
+            {
+        ;
+            }
+
+            for (d = kMinD; d <= kMaxD; d += 2)
+            {
+                FASTCOVER_ctx_t ctx;
+
+                if (displayLevel >= 3)
+                {
+        ;
+                }
+
+
+                {
+                    nuint initVal = FASTCOVER_ctx_init(&ctx, samplesBuffer, samplesSizes, nbSamples, d, splitPoint, f, accelParams);
+
+                    if ((ERR_isError(initVal)) != 0)
+                    {
+                        if (displayLevel >= 1)
+                        {
+        ;
+                        }
+
+                        COVER_best_destroy(&best);
+                        return initVal;
+                    }
+                }
+
+                if (warned == 0)
+                {
+                    COVER_warnOnSmallCorpus(dictBufferCapacity, ctx.nbDmers, displayLevel);
+                    warned = 1;
+                }
+
+                for (k = kMinK; k <= kMaxK; k += kStepSize)
+                {
+                    FASTCOVER_tryParameters_data_s* data = (FASTCOVER_tryParameters_data_s*)(malloc((nuint)(sizeof(FASTCOVER_tryParameters_data_s))));
+
+                    if (displayLevel >= 3)
+                    {
+        ;
+                    }
+
+                    if (data == null)
+                    {
+                        if (displayLevel >= 1)
+                        {
+        ;
+                        }
+
+                        COVER_best_destroy(&best);
+                        FASTCOVER_ctx_destroy(&ctx);
+                        return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_memory_allocation)));
+                    }
+
+                    data->ctx = &ctx;
+                    data->best = &best;
+                    data->dictBufferCapacity = dictBufferCapacity;
+                    data->parameters = coverParams;
+                    data->parameters.k = k;
+                    data->parameters.d = d;
+                    data->parameters.splitPoint = splitPoint;
+                    data->parameters.steps = kSteps;
+                    data->parameters.shrinkDict = shrinkDict;
+                    data->parameters.zParams.notificationLevel = (uint)g_displayLevel;
+                    if ((FASTCOVER_checkParameters(data->parameters, dictBufferCapacity, data->ctx->f, accel)) == 0)
+                    {
+                        free((void*)data);
+                        continue;
+                    }
+
+                    COVER_best_start(&best);
+                    FASTCOVER_tryParameters((void*)data);
+
+                    ++iteration;
+                }
+
+                COVER_best_wait(&best);
+                FASTCOVER_ctx_destroy(&ctx);
+            }
+
+            if (displayLevel >= 2)
+            {
+        ;
+            }
+
+
+            {
+                nuint dictSize = best.dictSize;
+
+                if ((ERR_isError(best.compressedSize)) != 0)
+                {
+                    nuint compressedSize = best.compressedSize;
+
+                    COVER_best_destroy(&best);
+                    return compressedSize;
+                }
+
+                FASTCOVER_convertToFastCoverParams(best.parameters, parameters, f, accel);
+                memcpy(dictBuffer, best.dict, dictSize);
+                COVER_best_destroy(&best);
+                return dictSize;
+            }
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/Fse.cs

@@ -0,0 +1,158 @@
+using System;
+using System.Runtime.CompilerServices;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void FSE_initCState(FSE_CState_t* statePtr, uint* ct)
+        {
+            void* ptr = (void*)ct;
+            ushort* u16ptr = (ushort*)(ptr);
+            uint tableLog = MEM_read16(ptr);
+
+            statePtr->value = (nint)(1) << (int)tableLog;
+            statePtr->stateTable = u16ptr + 2;
+            statePtr->symbolTT = ct + 1 + (tableLog != 0 ? (1 << (int)(tableLog - 1)) : 1);
+            statePtr->stateLog = tableLog;
+        }
+
+        /*! FSE_initCState2() :
+        *   Same as FSE_initCState(), but the first symbol to include (which will be the last to be read)
+        *   uses the smallest state value possible, saving the cost of this symbol */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void FSE_initCState2(FSE_CState_t* statePtr, uint* ct, uint symbol)
+        {
+            FSE_initCState(statePtr, ct);
+
+            {
+                FSE_symbolCompressionTransform symbolTT = ((FSE_symbolCompressionTransform*)(statePtr->symbolTT))[symbol];
+                ushort* stateTable = (ushort*)(statePtr->stateTable);
+                uint nbBitsOut = (uint)((symbolTT.deltaNbBits + (uint)((1 << 15))) >> 16);
+
+                statePtr->value = (nint)((nbBitsOut << 16) - symbolTT.deltaNbBits);
+                statePtr->value = (nint)(stateTable[(statePtr->value >> (int)nbBitsOut) + symbolTT.deltaFindState]);
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void FSE_encodeSymbol(BIT_CStream_t* bitC, FSE_CState_t* statePtr, uint symbol)
+        {
+            FSE_symbolCompressionTransform symbolTT = ((FSE_symbolCompressionTransform*)(statePtr->symbolTT))[symbol];
+            ushort* stateTable = (ushort*)(statePtr->stateTable);
+            uint nbBitsOut = (uint)(((nuint)statePtr->value + symbolTT.deltaNbBits) >> 16);
+
+            BIT_addBits(bitC, (nuint)statePtr->value, nbBitsOut);
+            statePtr->value = (nint)(stateTable[(statePtr->value >> (int)nbBitsOut) + symbolTT.deltaFindState]);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void FSE_flushCState(BIT_CStream_t* bitC, FSE_CState_t* statePtr)
+        {
+            BIT_addBits(bitC, (nuint)statePtr->value, statePtr->stateLog);
+            BIT_flushBits(bitC);
+        }
+
+        /* FSE_getMaxNbBits() :
+         * Approximate maximum cost of a symbol, in bits.
+         * Fractional get rounded up (i.e : a symbol with a normalized frequency of 3 gives the same result as a frequency of 2)
+         * note 1 : assume symbolValue is valid (<= maxSymbolValue)
+         * note 2 : if freq[symbolValue]==0, @return a fake cost of tableLog+1 bits */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint FSE_getMaxNbBits(void* symbolTTPtr, uint symbolValue)
+        {
+            FSE_symbolCompressionTransform* symbolTT = (FSE_symbolCompressionTransform*)(symbolTTPtr);
+
+            return (symbolTT[symbolValue].deltaNbBits + (uint)(((1 << 16) - 1))) >> 16;
+        }
+
+        /* FSE_bitCost() :
+         * Approximate symbol cost, as fractional value, using fixed-point format (accuracyLog fractional bits)
+         * note 1 : assume symbolValue is valid (<= maxSymbolValue)
+         * note 2 : if freq[symbolValue]==0, @return a fake cost of tableLog+1 bits */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint FSE_bitCost(void* symbolTTPtr, uint tableLog, uint symbolValue, uint accuracyLog)
+        {
+            FSE_symbolCompressionTransform* symbolTT = (FSE_symbolCompressionTransform*)(symbolTTPtr);
+            uint minNbBits = symbolTT[symbolValue].deltaNbBits >> 16;
+            uint threshold = (minNbBits + 1) << 16;
+
+            assert(tableLog < 16);
+            assert(accuracyLog < 31 - tableLog);
+
+            {
+                uint tableSize = (uint)(1 << (int)tableLog);
+                uint deltaFromThreshold = threshold - (symbolTT[symbolValue].deltaNbBits + tableSize);
+                uint normalizedDeltaFromThreshold = (deltaFromThreshold << (int)accuracyLog) >> (int)tableLog;
+                uint bitMultiplier = (uint)(1 << (int)accuracyLog);
+
+                assert(symbolTT[symbolValue].deltaNbBits + tableSize <= threshold);
+                assert(normalizedDeltaFromThreshold <= bitMultiplier);
+                return (minNbBits + 1) * bitMultiplier - normalizedDeltaFromThreshold;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void FSE_initDState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD, uint* dt)
+        {
+            void* ptr = (void*)dt;
+            FSE_DTableHeader* DTableH = (FSE_DTableHeader*)(ptr);
+
+            DStatePtr->state = BIT_readBits(bitD, DTableH->tableLog);
+            BIT_reloadDStream(bitD);
+            DStatePtr->table = dt + 1;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static byte FSE_peekSymbol(FSE_DState_t* DStatePtr)
+        {
+            FSE_decode_t DInfo = ((FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
+
+            return DInfo.symbol;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void FSE_updateState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
+        {
+            FSE_decode_t DInfo = ((FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
+            uint nbBits = DInfo.nbBits;
+            nuint lowBits = BIT_readBits(bitD, nbBits);
+
+            DStatePtr->state = DInfo.newState + lowBits;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static byte FSE_decodeSymbol(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
+        {
+            FSE_decode_t DInfo = ((FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
+            uint nbBits = DInfo.nbBits;
+            byte symbol = DInfo.symbol;
+            nuint lowBits = BIT_readBits(bitD, nbBits);
+
+            DStatePtr->state = DInfo.newState + lowBits;
+            return symbol;
+        }
+
+        /*! FSE_decodeSymbolFast() :
+            unsafe, only works if no symbol has a probability > 50% */
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static byte FSE_decodeSymbolFast(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD)
+        {
+            FSE_decode_t DInfo = ((FSE_decode_t*)(DStatePtr->table))[DStatePtr->state];
+            uint nbBits = DInfo.nbBits;
+            byte symbol = DInfo.symbol;
+            nuint lowBits = BIT_readBitsFast(bitD, nbBits);
+
+            DStatePtr->state = DInfo.newState + lowBits;
+            return symbol;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static uint FSE_endOfDState(FSE_DState_t* DStatePtr)
+        {
+            return ((DStatePtr->state == 0) ? 1U : 0U);
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FseCompress.cs

@@ -0,0 +1,960 @@
+using System;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        /* FSE_buildCTable_wksp() :
+         * Same as FSE_buildCTable(), but using an externally allocated scratch buffer (`workSpace`).
+         * wkspSize should be sized to handle worst case situation, which is `1<<max_tableLog * sizeof(FSE_FUNCTION_TYPE)`
+         * workSpace must also be properly aligned with FSE_FUNCTION_TYPE requirements
+         */
+        public static nuint FSE_buildCTable_wksp(uint* ct, short* normalizedCounter, uint maxSymbolValue, uint tableLog, void* workSpace, nuint wkspSize)
+        {
+            uint tableSize = (uint)(1 << (int)tableLog);
+            uint tableMask = tableSize - 1;
+            void* ptr = (void*)ct;
+            ushort* tableU16 = ((ushort*)(ptr)) + 2;
+            void* FSCT = (void*)(((uint*)(ptr)) + 1 + (tableLog != 0 ? tableSize >> 1 : 1));
+            FSE_symbolCompressionTransform* symbolTT = (FSE_symbolCompressionTransform*)(FSCT);
+            uint step = (((tableSize) >> 1) + ((tableSize) >> 3) + 3);
+            uint* cumul = (uint*)(workSpace);
+            byte* tableSymbol = (byte*)(cumul + (maxSymbolValue + 2));
+            uint highThreshold = tableSize - 1;
+
+            if (((nuint)(workSpace) & 3) != 0)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            }
+
+            if (((nuint)(sizeof(uint)) * (maxSymbolValue + 2 + (1UL << (int)(tableLog - 2)))) > wkspSize)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+            }
+
+            tableU16[-2] = (ushort)(tableLog);
+            tableU16[-1] = (ushort)(maxSymbolValue);
+            assert(tableLog < 16);
+
+            {
+                uint u;
+
+                cumul[0] = 0;
+                for (u = 1; u <= maxSymbolValue + 1; u++)
+                {
+                    if (normalizedCounter[u - 1] == -1)
+                    {
+                        cumul[u] = cumul[u - 1] + 1;
+                        tableSymbol[highThreshold--] = (byte)(u - 1);
+                    }
+                    else
+                    {
+                        cumul[u] = cumul[u - 1] + (ushort)(normalizedCounter[u - 1]);
+                    }
+                }
+
+                cumul[maxSymbolValue + 1] = tableSize + 1;
+            }
+
+
+            {
+                uint position = 0;
+                uint symbol;
+
+                for (symbol = 0; symbol <= maxSymbolValue; symbol++)
+                {
+                    int nbOccurrences;
+                    int freq = normalizedCounter[symbol];
+
+                    for (nbOccurrences = 0; nbOccurrences < freq; nbOccurrences++)
+                    {
+                        tableSymbol[position] = (byte)(symbol);
+                        position = (position + step) & tableMask;
+                        while (position > highThreshold)
+                        {
+                            position = (position + step) & tableMask;
+                        }
+                    }
+                }
+
+                assert(position == 0);
+            }
+
+
+            {
+                uint u;
+
+                for (u = 0; u < tableSize; u++)
+                {
+                    byte s = tableSymbol[u];
+
+                    tableU16[cumul[s]++] = (ushort)(tableSize + u);
+                }
+            }
+
+
+            {
+                uint total = 0;
+                uint s;
+
+                for (s = 0; s <= maxSymbolValue; s++)
+                {
+                    switch (normalizedCounter[s])
+                    {
+                        case 0:
+                        {
+                            symbolTT[s].deltaNbBits = ((tableLog + 1) << 16) - (uint)((1 << (int)tableLog));
+                        }
+
+                        break;
+                        case -1:
+                        case 1:
+                        {
+                            symbolTT[s].deltaNbBits = (tableLog << 16) - (uint)((1 << (int)tableLog));
+                        }
+
+                        symbolTT[s].deltaFindState = (int)(total - 1);
+                        total++;
+                        break;
+                        default:
+                        {
+                            uint maxBitsOut = tableLog - BIT_highbit32((uint)(normalizedCounter[s] - 1));
+                            uint minStatePlus = (uint)(normalizedCounter[s] << (int)maxBitsOut);
+
+                            symbolTT[s].deltaNbBits = (maxBitsOut << 16) - minStatePlus;
+                            symbolTT[s].deltaFindState = (int)(total - (ushort)(normalizedCounter[s]));
+                            total += (uint)(normalizedCounter[s]);
+                        }
+                        break;
+                    }
+                }
+            }
+
+            return 0;
+        }
+
+        /*! FSE_buildCTable():
+            Builds `ct`, which must be already allocated, using FSE_createCTable().
+            @return : 0, or an errorCode, which can be tested using FSE_isError() */
+        public static nuint FSE_buildCTable(uint* ct, short* normalizedCounter, uint maxSymbolValue, uint tableLog)
+        {
+            byte* tableSymbol = stackalloc byte[4096];
+
+            return FSE_buildCTable_wksp(ct, normalizedCounter, maxSymbolValue, tableLog, (void*)tableSymbol, (nuint)(sizeof(byte) * 4096));
+        }
+
+        /*-**************************************************************
+        *  FSE NCount encoding
+        ****************************************************************/
+        public static nuint FSE_NCountWriteBound(uint maxSymbolValue, uint tableLog)
+        {
+            nuint maxHeaderSize = (((maxSymbolValue + 1) * tableLog) >> 3) + 3;
+
+            return maxSymbolValue != 0 ? maxHeaderSize : 512;
+        }
+
+        private static nuint FSE_writeNCount_generic(void* header, nuint headerBufferSize, short* normalizedCounter, uint maxSymbolValue, uint tableLog, uint writeIsSafe)
+        {
+            byte* ostart = (byte*)(header);
+            byte* @out = ostart;
+            byte* oend = ostart + headerBufferSize;
+            int nbBits;
+            int tableSize = 1 << (int)tableLog;
+            int remaining;
+            int threshold;
+            uint bitStream = 0;
+            int bitCount = 0;
+            uint symbol = 0;
+            uint alphabetSize = maxSymbolValue + 1;
+            int previousIs0 = 0;
+
+            bitStream += (tableLog - 5) << bitCount;
+            bitCount += 4;
+            remaining = tableSize + 1;
+            threshold = tableSize;
+            nbBits = (int)(tableLog + 1);
+            while ((symbol < alphabetSize) && (remaining > 1))
+            {
+                if (previousIs0 != 0)
+                {
+                    uint start = symbol;
+
+                    while ((symbol < alphabetSize) && (normalizedCounter[symbol]) == 0)
+                    {
+                        symbol++;
+                    }
+
+                    if (symbol == alphabetSize)
+                    {
+                        break;
+                    }
+
+                    while (symbol >= start + 24)
+                    {
+                        start += 24;
+                        bitStream += 0xFFFFU << bitCount;
+                        if (writeIsSafe == 0 && (@out > oend - 2))
+                        {
+                            return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+                        }
+
+                        @out[0] = (byte)(bitStream);
+                        @out[1] = (byte)(bitStream >> 8);
+                        @out += 2;
+                        bitStream >>= 16;
+                    }
+
+                    while (symbol >= start + 3)
+                    {
+                        start += 3;
+                        bitStream += (uint)(3 << bitCount);
+                        bitCount += 2;
+                    }
+
+                    bitStream += (symbol - start) << bitCount;
+                    bitCount += 2;
+                    if (bitCount > 16)
+                    {
+                        if (writeIsSafe == 0 && (@out > oend - 2))
+                        {
+                            return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+                        }
+
+                        @out[0] = (byte)(bitStream);
+                        @out[1] = (byte)(bitStream >> 8);
+                        @out += 2;
+                        bitStream >>= 16;
+                        bitCount -= 16;
+                    }
+                }
+
+
+                {
+                    int count = normalizedCounter[symbol++];
+                    int max = (2 * threshold - 1) - remaining;
+
+                    remaining -= count < 0 ? -count : count;
+                    count++;
+                    if (count >= threshold)
+                    {
+                        count += max;
+                    }
+
+                    bitStream += (uint)(count << bitCount);
+                    bitCount += nbBits;
+                    bitCount -= ((count < max) ? 1 : 0);
+                    previousIs0 = ((count == 1) ? 1 : 0);
+                    if (remaining < 1)
+                    {
+                        return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+                    }
+
+                    while (remaining < threshold)
+                    {
+                        nbBits--;
+                        threshold >>= 1;
+                    }
+                }
+
+                if (bitCount > 16)
+                {
+                    if (writeIsSafe == 0 && (@out > oend - 2))
+                    {
+                        return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+                    }
+
+                    @out[0] = (byte)(bitStream);
+                    @out[1] = (byte)(bitStream >> 8);
+                    @out += 2;
+                    bitStream >>= 16;
+                    bitCount -= 16;
+                }
+            }
+
+            if (remaining != 1)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            }
+
+            assert(symbol <= alphabetSize);
+            if (writeIsSafe == 0 && (@out > oend - 2))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+            }
+
+            @out[0] = (byte)(bitStream);
+            @out[1] = (byte)(bitStream >> 8);
+            @out += (bitCount + 7) / 8;
+            return (nuint)((@out - ostart));
+        }
+
+        /*! FSE_writeNCount():
+            Compactly save 'normalizedCounter' into 'buffer'.
+            @return : size of the compressed table,
+                      or an errorCode, which can be tested using FSE_isError(). */
+        public static nuint FSE_writeNCount(void* buffer, nuint bufferSize, short* normalizedCounter, uint maxSymbolValue, uint tableLog)
+        {
+            if (tableLog > (uint)((14 - 2)))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+            }
+
+            if (tableLog < 5)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            }
+
+            if (bufferSize < FSE_NCountWriteBound(maxSymbolValue, tableLog))
+            {
+                return FSE_writeNCount_generic(buffer, bufferSize, normalizedCounter, maxSymbolValue, tableLog, 0);
+            }
+
+            return FSE_writeNCount_generic(buffer, bufferSize, normalizedCounter, maxSymbolValue, tableLog, 1);
+        }
+
+        /*-**************************************************************
+        *  FSE Compression Code
+        ****************************************************************/
+        public static uint* FSE_createCTable(uint maxSymbolValue, uint tableLog)
+        {
+            nuint size;
+
+            if (tableLog > 15)
+            {
+                tableLog = 15;
+            }
+
+            size = ((uint)(1 + (1 << (int)((tableLog) - 1))) + (((maxSymbolValue) + 1) * 2)) * (nuint)(sizeof(uint));
+            return (uint*)(malloc(size));
+        }
+
+        public static void FSE_freeCTable(uint* ct)
+        {
+            free((void*)(ct));
+        }
+
+        /* provides the minimum logSize to safely represent a distribution */
+        [InlineMethod.Inline]
+        private static uint FSE_minTableLog(nuint srcSize, uint maxSymbolValue)
+        {
+            uint minBitsSrc = BIT_highbit32((uint)(srcSize)) + 1;
+            uint minBitsSymbols = BIT_highbit32(maxSymbolValue) + 2;
+            uint minBits = minBitsSrc < minBitsSymbols ? minBitsSrc : minBitsSymbols;
+
+            assert(srcSize > 1);
+            return minBits;
+        }
+
+        /* *****************************************
+         *  FSE advanced API
+         ***************************************** */
+        public static uint FSE_optimalTableLog_internal(uint maxTableLog, nuint srcSize, uint maxSymbolValue, uint minus)
+        {
+            uint maxBitsSrc = BIT_highbit32((uint)(srcSize - 1)) - minus;
+            uint tableLog = maxTableLog;
+            uint minBits = FSE_minTableLog(srcSize, maxSymbolValue);
+
+            assert(srcSize > 1);
+            if (tableLog == 0)
+            {
+                tableLog = (uint)((13 - 2));
+            }
+
+            if (maxBitsSrc < tableLog)
+            {
+                tableLog = maxBitsSrc;
+            }
+
+            if (minBits > tableLog)
+            {
+                tableLog = minBits;
+            }
+
+            if (tableLog < 5)
+            {
+                tableLog = 5;
+            }
+
+            if (tableLog > (uint)((14 - 2)))
+            {
+                tableLog = (uint)((14 - 2));
+            }
+
+            return tableLog;
+        }
+
+        /*! FSE_optimalTableLog():
+            dynamically downsize 'tableLog' when conditions are met.
+            It saves CPU time, by using smaller tables, while preserving or even improving compression ratio.
+            @return : recommended tableLog (necessarily <= 'maxTableLog') */
+        public static uint FSE_optimalTableLog(uint maxTableLog, nuint srcSize, uint maxSymbolValue)
+        {
+            return FSE_optimalTableLog_internal(maxTableLog, srcSize, maxSymbolValue, 2);
+        }
+
+        /* Secondary normalization method.
+           To be used when primary method fails. */
+        private static nuint FSE_normalizeM2(short* norm, uint tableLog, uint* count, nuint total, uint maxSymbolValue, short lowProbCount)
+        {
+            short NOT_YET_ASSIGNED = (short)-2;
+            uint s;
+            uint distributed = 0;
+            uint ToDistribute;
+            uint lowThreshold = (uint)(total >> (int)tableLog);
+            uint lowOne = (uint)((total * 3) >> (int)(tableLog + 1));
+
+            for (s = 0; s <= maxSymbolValue; s++)
+            {
+                if (count[s] == 0)
+                {
+                    norm[s] = 0;
+                    continue;
+                }
+
+                if (count[s] <= lowThreshold)
+                {
+                    norm[s] = lowProbCount;
+                    distributed++;
+                    total -= count[s];
+                    continue;
+                }
+
+                if (count[s] <= lowOne)
+                {
+                    norm[s] = 1;
+                    distributed++;
+                    total -= count[s];
+                    continue;
+                }
+
+                norm[s] = NOT_YET_ASSIGNED;
+            }
+
+            ToDistribute = (uint)((1 << (int)tableLog)) - distributed;
+            if (ToDistribute == 0)
+            {
+                return 0;
+            }
+
+            if ((total / ToDistribute) > lowOne)
+            {
+                lowOne = (uint)((total * 3) / (ToDistribute * 2));
+                for (s = 0; s <= maxSymbolValue; s++)
+                {
+                    if ((norm[s] == NOT_YET_ASSIGNED) && (count[s] <= lowOne))
+                    {
+                        norm[s] = 1;
+                        distributed++;
+                        total -= count[s];
+                        continue;
+                    }
+                }
+
+                ToDistribute = (uint)((1 << (int)tableLog)) - distributed;
+            }
+
+            if (distributed == maxSymbolValue + 1)
+            {
+                uint maxV = 0, maxC = 0;
+
+                for (s = 0; s <= maxSymbolValue; s++)
+                {
+                    if (count[s] > maxC)
+                    {
+                        maxV = s;
+                        maxC = count[s];
+                    }
+                }
+
+                norm[maxV] += (short)(short)(ToDistribute);
+                return 0;
+            }
+
+            if (total == 0)
+            {
+                for (s = 0; ToDistribute > 0; s = (s + 1) % (maxSymbolValue + 1))
+                {
+                    if (norm[s] > 0)
+                    {
+                        ToDistribute--;
+                        norm[s]++;
+                    }
+                }
+
+                return 0;
+            }
+
+
+            {
+                ulong vStepLog = 62 - tableLog;
+                ulong mid = (1UL << (int)(vStepLog - 1)) - 1;
+                ulong rStep = (((((ulong)(1) << (int)vStepLog) * ToDistribute) + mid) / ((uint)(total)));
+                ulong tmpTotal = mid;
+
+                for (s = 0; s <= maxSymbolValue; s++)
+                {
+                    if (norm[s] == NOT_YET_ASSIGNED)
+                    {
+                        ulong end = tmpTotal + (count[s] * rStep);
+                        uint sStart = (uint)(tmpTotal >> (int)vStepLog);
+                        uint sEnd = (uint)(end >> (int)vStepLog);
+                        uint weight = sEnd - sStart;
+
+                        if (weight < 1)
+                        {
+                            return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+                        }
+
+                        norm[s] = (short)(weight);
+                        tmpTotal = end;
+                    }
+                }
+            }
+
+            return 0;
+        }
+
+        /*! FSE_normalizeCount():
+            normalize counts so that sum(count[]) == Power_of_2 (2^tableLog)
+            'normalizedCounter' is a table of short, of minimum size (maxSymbolValue+1).
+            useLowProbCount is a boolean parameter which trades off compressed size for
+            faster header decoding. When it is set to 1, the compressed data will be slightly
+            smaller. And when it is set to 0, FSE_readNCount() and FSE_buildDTable() will be
+            faster. If you are compressing a small amount of data (< 2 KB) then useLowProbCount=0
+            is a good default, since header deserialization makes a big speed difference.
+            Otherwise, useLowProbCount=1 is a good default, since the speed difference is small.
+            @return : tableLog,
+                      or an errorCode, which can be tested using FSE_isError() */
+        public static nuint FSE_normalizeCount(short* normalizedCounter, uint tableLog, uint* count, nuint total, uint maxSymbolValue, uint useLowProbCount)
+        {
+            if (tableLog == 0)
+            {
+                tableLog = (uint)((13 - 2));
+            }
+
+            if (tableLog < 5)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            }
+
+            if (tableLog > (uint)((14 - 2)))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+            }
+
+            if (tableLog < FSE_minTableLog(total, maxSymbolValue))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            }
+
+
+            {
+
+                short lowProbCount = (short)(useLowProbCount != 0 ? -1 : 1);
+                ulong scale = 62 - tableLog;
+                ulong step = (((ulong)(1) << 62) / ((uint)(total)));
+                ulong vStep = 1UL << (int)(scale - 20);
+                int stillToDistribute = 1 << (int)tableLog;
+                uint s;
+                uint largest = 0;
+                short largestP = 0;
+                uint lowThreshold = (uint)(total >> (int)tableLog);
+
+                for (s = 0; s <= maxSymbolValue; s++)
+                {
+                    if (count[s] == total)
+                    {
+                        return 0;
+                    }
+
+                    if (count[s] == 0)
+                    {
+                        normalizedCounter[s] = 0;
+                        continue;
+                    }
+
+                    if (count[s] <= lowThreshold)
+                    {
+                        normalizedCounter[s] = lowProbCount;
+                        stillToDistribute--;
+                    }
+                    else
+                    {
+                        short proba = (short)((count[s] * step) >> (int)scale);
+
+                        if (proba < 8)
+                        {
+                            ulong restToBeat = vStep * rtbTable[proba];
+
+                            proba += (short)((((count[s] * step) - ((ulong)(proba) << (int)scale) > restToBeat) ? 1 : 0));
+                        }
+
+                        if (proba > largestP)
+                        {
+                            largestP = proba;
+                            largest = s;
+                        }
+
+                        normalizedCounter[s] = proba;
+                        stillToDistribute -= proba;
+                    }
+                }
+
+                if (-stillToDistribute >= (normalizedCounter[largest] >> 1))
+                {
+                    nuint errorCode = FSE_normalizeM2(normalizedCounter, tableLog, count, total, maxSymbolValue, lowProbCount);
+
+                    if ((ERR_isError(errorCode)) != 0)
+                    {
+                        return errorCode;
+                    }
+                }
+                else
+                {
+                    normalizedCounter[largest] += (short)(short)(stillToDistribute);
+                }
+            }
+
+            return tableLog;
+        }
+
+        /* fake FSE_CTable, for raw (uncompressed) input */
+        public static nuint FSE_buildCTable_raw(uint* ct, uint nbBits)
+        {
+            uint tableSize = (uint)(1 << (int)nbBits);
+            uint tableMask = tableSize - 1;
+            uint maxSymbolValue = tableMask;
+            void* ptr = (void*)ct;
+            ushort* tableU16 = ((ushort*)(ptr)) + 2;
+            void* FSCT = (void*)(((uint*)(ptr)) + 1 + (tableSize >> 1));
+            FSE_symbolCompressionTransform* symbolTT = (FSE_symbolCompressionTransform*)(FSCT);
+            uint s;
+
+            if (nbBits < 1)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            }
+
+            tableU16[-2] = (ushort)(nbBits);
+            tableU16[-1] = (ushort)(maxSymbolValue);
+            for (s = 0; s < tableSize; s++)
+            {
+                tableU16[s] = (ushort)(tableSize + s);
+            }
+
+
+            {
+                uint deltaNbBits = (nbBits << 16) - (uint)((1 << (int)nbBits));
+
+                for (s = 0; s <= maxSymbolValue; s++)
+                {
+                    symbolTT[s].deltaNbBits = deltaNbBits;
+                    symbolTT[s].deltaFindState = (int)(s - 1);
+                }
+            }
+
+            return 0;
+        }
+
+        /* fake FSE_CTable, for rle input (always same symbol) */
+        public static nuint FSE_buildCTable_rle(uint* ct, byte symbolValue)
+        {
+            void* ptr = (void*)ct;
+            ushort* tableU16 = ((ushort*)(ptr)) + 2;
+            void* FSCTptr = (void*)((uint*)(ptr) + 2);
+            FSE_symbolCompressionTransform* symbolTT = (FSE_symbolCompressionTransform*)(FSCTptr);
+
+            tableU16[-2] = (ushort)(0);
+            tableU16[-1] = (ushort)(symbolValue);
+            tableU16[0] = 0;
+            tableU16[1] = 0;
+            symbolTT[symbolValue].deltaNbBits = 0;
+            symbolTT[symbolValue].deltaFindState = 0;
+            return 0;
+        }
+
+        private static nuint FSE_compress_usingCTable_generic(void* dst, nuint dstSize, void* src, nuint srcSize, uint* ct, uint fast)
+        {
+            byte* istart = (byte*)(src);
+            byte* iend = istart + srcSize;
+            byte* ip = iend;
+            BIT_CStream_t bitC;
+            FSE_CState_t CState1, CState2;
+
+            if (srcSize <= 2)
+            {
+                return 0;
+            }
+
+
+            {
+                nuint initError = BIT_initCStream(&bitC, dst, dstSize);
+
+                if ((ERR_isError(initError)) != 0)
+                {
+                    return 0;
+                }
+            }
+
+            if ((srcSize & 1) != 0)
+            {
+                FSE_initCState2(&CState1, ct, *--ip);
+                FSE_initCState2(&CState2, ct, *--ip);
+                FSE_encodeSymbol(&bitC, &CState1, *--ip);
+                if (fast != 0)
+                {
+                    BIT_flushBitsFast(&bitC);
+                }
+                else
+                {
+                    BIT_flushBits(&bitC);
+                }
+
+            }
+            else
+            {
+                FSE_initCState2(&CState2, ct, *--ip);
+                FSE_initCState2(&CState1, ct, *--ip);
+            }
+
+            srcSize -= 2;
+            if (((nuint)(sizeof(nuint)) * 8 > (uint)((14 - 2) * 4 + 7)) && (srcSize & 2) != 0)
+            {
+                FSE_encodeSymbol(&bitC, &CState2, *--ip);
+                FSE_encodeSymbol(&bitC, &CState1, *--ip);
+                if (fast != 0)
+                {
+                    BIT_flushBitsFast(&bitC);
+                }
+                else
+                {
+                    BIT_flushBits(&bitC);
+                }
+
+            }
+
+            while (ip > istart)
+            {
+                FSE_encodeSymbol(&bitC, &CState2, *--ip);
+                if ((nuint)(sizeof(nuint)) * 8 < (uint)((14 - 2) * 2 + 7))
+                {
+                    if (fast != 0)
+                    {
+                        BIT_flushBitsFast(&bitC);
+                    }
+                    else
+                    {
+                        BIT_flushBits(&bitC);
+                    }
+                }
+
+                FSE_encodeSymbol(&bitC, &CState1, *--ip);
+                if ((nuint)(sizeof(nuint)) * 8 > (uint)((14 - 2) * 4 + 7))
+                {
+                    FSE_encodeSymbol(&bitC, &CState2, *--ip);
+                    FSE_encodeSymbol(&bitC, &CState1, *--ip);
+                }
+
+                if (fast != 0)
+                {
+                    BIT_flushBitsFast(&bitC);
+                }
+                else
+                {
+                    BIT_flushBits(&bitC);
+                }
+
+            }
+
+            FSE_flushCState(&bitC, &CState2);
+            FSE_flushCState(&bitC, &CState1);
+            return BIT_closeCStream(&bitC);
+        }
+
+        /*! FSE_compress_usingCTable():
+            Compress `src` using `ct` into `dst` which must be already allocated.
+            @return : size of compressed data (<= `dstCapacity`),
+                      or 0 if compressed data could not fit into `dst`,
+                      or an errorCode, which can be tested using FSE_isError() */
+        public static nuint FSE_compress_usingCTable(void* dst, nuint dstSize, void* src, nuint srcSize, uint* ct)
+        {
+            uint fast = (((dstSize >= ((srcSize) + ((srcSize) >> 7) + 4 + (nuint)(sizeof(nuint))))) ? 1U : 0U);
+
+            if (fast != 0)
+            {
+                return FSE_compress_usingCTable_generic(dst, dstSize, src, srcSize, ct, 1);
+            }
+            else
+            {
+                return FSE_compress_usingCTable_generic(dst, dstSize, src, srcSize, ct, 0);
+            }
+        }
+
+        /*-*****************************************
+        *  Tool functions
+        ******************************************/
+        public static nuint FSE_compressBound(nuint size)
+        {
+            return (512 + ((size) + ((size) >> 7) + 4 + (nuint)(sizeof(nuint))));
+        }
+
+        /* FSE_compress_wksp() :
+         * Same as FSE_compress2(), but using an externally allocated scratch buffer (`workSpace`).
+         * `wkspSize` size must be `(1<<tableLog)`.
+         */
+        public static nuint FSE_compress_wksp(void* dst, nuint dstSize, void* src, nuint srcSize, uint maxSymbolValue, uint tableLog, void* workSpace, nuint wkspSize)
+        {
+            byte* ostart = (byte*)(dst);
+            byte* op = ostart;
+            byte* oend = ostart + dstSize;
+            uint* count = stackalloc uint[256];
+            short* norm = stackalloc short[256];
+            uint* CTable = (uint*)(workSpace);
+            nuint CTableSize = ((uint)(1 + (1 << (int)((tableLog) - 1))) + (((maxSymbolValue) + 1) * 2));
+            void* scratchBuffer = (void*)(CTable + CTableSize);
+            nuint scratchBufferSize = wkspSize - (CTableSize * (nuint)(4));
+
+            if (wkspSize < (((uint)(1 + (1 << (int)((tableLog) - 1))) + (((maxSymbolValue) + 1) * 2)) + (uint)(((tableLog > 12) ? (1 << (int)(tableLog - 2)) : 1024))))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+            }
+
+            if (srcSize <= 1)
+            {
+                return 0;
+            }
+
+            if (maxSymbolValue == 0)
+            {
+                maxSymbolValue = 255;
+            }
+
+            if (tableLog == 0)
+            {
+                tableLog = (uint)((13 - 2));
+            }
+
+
+            {
+                nuint maxCount = HIST_count_wksp((uint*)count, &maxSymbolValue, src, srcSize, scratchBuffer, scratchBufferSize);
+
+                if ((ERR_isError(maxCount)) != 0)
+                {
+                    return maxCount;
+                }
+
+                if (maxCount == srcSize)
+                {
+                    return 1;
+                }
+
+                if (maxCount == 1)
+                {
+                    return 0;
+                }
+
+                if (maxCount < (srcSize >> 7))
+                {
+                    return 0;
+                }
+            }
+
+            tableLog = FSE_optimalTableLog(tableLog, srcSize, maxSymbolValue);
+
+            {
+                nuint _var_err__ = FSE_normalizeCount((short*)norm, tableLog, (uint*)count, srcSize, maxSymbolValue, ((srcSize >= 2048) ? 1U : 0U));
+
+                if ((ERR_isError(_var_err__)) != 0)
+                {
+                    return _var_err__;
+                }
+            }
+
+
+            {
+                nuint nc_err = FSE_writeNCount((void*)op, (nuint)(oend - op), (short*)norm, maxSymbolValue, tableLog);
+
+                if ((ERR_isError(nc_err)) != 0)
+                {
+                    return nc_err;
+                }
+
+                op += nc_err;
+            }
+
+
+            {
+                nuint _var_err__ = FSE_buildCTable_wksp(CTable, (short*)norm, maxSymbolValue, tableLog, scratchBuffer, scratchBufferSize);
+
+                if ((ERR_isError(_var_err__)) != 0)
+                {
+                    return _var_err__;
+                }
+            }
+
+
+            {
+                nuint cSize = FSE_compress_usingCTable((void*)op, (nuint)(oend - op), src, srcSize, CTable);
+
+                if ((ERR_isError(cSize)) != 0)
+                {
+                    return cSize;
+                }
+
+                if (cSize == 0)
+                {
+                    return 0;
+                }
+
+                op += cSize;
+            }
+
+            if ((nuint)(op - ostart) >= srcSize - 1)
+            {
+                return 0;
+            }
+
+            return (nuint)(op - ostart);
+        }
+
+        /*-*****************************************
+        *  FSE advanced functions
+        ******************************************/
+        /*! FSE_compress2() :
+            Same as FSE_compress(), but allows the selection of 'maxSymbolValue' and 'tableLog'
+            Both parameters can be defined as '0' to mean : use default value
+            @return : size of compressed data
+            Special values : if return == 0, srcData is not compressible => Nothing is stored within cSrc !!!
+                             if return == 1, srcData is a single byte symbol * srcSize times. Use RLE compression.
+                             if FSE_isError(return), it's an error code.
+        */
+        public static nuint FSE_compress2(void* dst, nuint dstCapacity, void* src, nuint srcSize, uint maxSymbolValue, uint tableLog)
+        {
+            fseWkspMax_t scratchBuffer;
+
+            if (tableLog > (uint)((14 - 2)))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+            }
+
+            return FSE_compress_wksp(dst, dstCapacity, src, srcSize, maxSymbolValue, tableLog, (void*)&scratchBuffer, (nuint)(sizeof(fseWkspMax_t)));
+        }
+
+        /*-****************************************
+        *  FSE simple functions
+        ******************************************/
+        /*! FSE_compress() :
+            Compress content of buffer 'src', of size 'srcSize', into destination buffer 'dst'.
+            'dst' buffer must be already allocated. Compression runs faster is dstCapacity >= FSE_compressBound(srcSize).
+            @return : size of compressed data (<= dstCapacity).
+            Special values : if return == 0, srcData is not compressible => Nothing is stored within dst !!!
+                             if return == 1, srcData is a single byte symbol * srcSize times. Use RLE compression instead.
+                             if FSE_isError(return), compression failed (more details using FSE_getErrorName())
+        */
+        public static nuint FSE_compress(void* dst, nuint dstCapacity, void* src, nuint srcSize)
+        {
+            return FSE_compress2(dst, dstCapacity, src, srcSize, 255, (uint)((13 - 2)));
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/FseDecompress.cs

@@ -0,0 +1,446 @@
+using System;
+using System.Runtime.CompilerServices;
+using static ZstdSharp.UnsafeHelper;
+
+namespace ZstdSharp.Unsafe
+{
+    public static unsafe partial class Methods
+    {
+        /* Function templates */
+        public static uint* FSE_createDTable(uint tableLog)
+        {
+            if (tableLog > 15)
+            {
+                tableLog = 15;
+            }
+
+            return (uint*)(malloc((uint)((1 + (1 << (int)(tableLog)))) * (nuint)(sizeof(uint))));
+        }
+
+        public static void FSE_freeDTable(uint* dt)
+        {
+            free((void*)(dt));
+        }
+
+        private static nuint FSE_buildDTable_internal(uint* dt, short* normalizedCounter, uint maxSymbolValue, uint tableLog, void* workSpace, nuint wkspSize)
+        {
+            void* tdPtr = (void*)(dt + 1);
+            FSE_decode_t* tableDecode = (FSE_decode_t*)(tdPtr);
+            ushort* symbolNext = (ushort*)(workSpace);
+            byte* spread = (byte*)(symbolNext + maxSymbolValue + 1);
+            uint maxSV1 = maxSymbolValue + 1;
+            uint tableSize = (uint)(1 << (int)tableLog);
+            uint highThreshold = tableSize - 1;
+
+            if (((nuint)(sizeof(short)) * (maxSymbolValue + 1) + (1UL << (int)tableLog) + 8) > wkspSize)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_maxSymbolValue_tooLarge)));
+            }
+
+            if (maxSymbolValue > 255)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_maxSymbolValue_tooLarge)));
+            }
+
+            if (tableLog > (uint)((14 - 2)))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+            }
+
+
+            {
+                FSE_DTableHeader DTableH;
+
+                DTableH.tableLog = (ushort)(tableLog);
+                DTableH.fastMode = 1;
+
+                {
+                    short largeLimit = (short)(1 << (int)(tableLog - 1));
+                    uint s;
+
+                    for (s = 0; s < maxSV1; s++)
+                    {
+                        if (normalizedCounter[s] == -1)
+                        {
+                            tableDecode[highThreshold--].symbol = (byte)(s);
+                            symbolNext[s] = 1;
+                        }
+                        else
+                        {
+                            if (normalizedCounter[s] >= largeLimit)
+                            {
+                                DTableH.fastMode = 0;
+                            }
+
+                            symbolNext[s] = (ushort)(normalizedCounter[s]);
+                        }
+                    }
+                }
+
+                memcpy((void*)(dt), (void*)(&DTableH), ((nuint)(sizeof(FSE_DTableHeader))));
+            }
+
+            if (highThreshold == tableSize - 1)
+            {
+                nuint tableMask = tableSize - 1;
+                nuint step = (((tableSize) >> 1) + ((tableSize) >> 3) + 3);
+
+
+                {
+                    ulong add = 0x0101010101010101UL;
+                    nuint pos = 0;
+                    ulong sv = 0;
+                    uint s;
+
+                    for (s = 0; s < maxSV1; ++s , sv += add)
+                    {
+                        int i;
+                        int n = normalizedCounter[s];
+
+                        MEM_write64((void*)(spread + pos), sv);
+                        for (i = 8; i < n; i += 8)
+                        {
+                            MEM_write64((void*)(spread + pos + i), sv);
+                        }
+
+                        pos += (nuint)n;
+                    }
+                }
+
+
+                {
+                    nuint position = 0;
+                    nuint s;
+                    nuint unroll = 2;
+
+                    assert(tableSize % unroll == 0);
+                    for (s = 0; s < (nuint)(tableSize); s += unroll)
+                    {
+                        nuint u;
+
+                        for (u = 0; u < unroll; ++u)
+                        {
+                            nuint uPosition = (position + (u * step)) & tableMask;
+
+                            tableDecode[uPosition].symbol = spread[s + u];
+                        }
+
+                        position = (position + (unroll * step)) & tableMask;
+                    }
+
+                    assert(position == 0);
+                }
+            }
+            else
+            {
+                uint tableMask = tableSize - 1;
+                uint step = (((tableSize) >> 1) + ((tableSize) >> 3) + 3);
+                uint s, position = 0;
+
+                for (s = 0; s < maxSV1; s++)
+                {
+                    int i;
+
+                    for (i = 0; i < normalizedCounter[s]; i++)
+                    {
+                        tableDecode[position].symbol = (byte)(s);
+                        position = (position + step) & tableMask;
+                        while (position > highThreshold)
+                        {
+                            position = (position + step) & tableMask;
+                        }
+                    }
+                }
+
+                if (position != 0)
+                {
+                    return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+                }
+            }
+
+
+            {
+                uint u;
+
+                for (u = 0; u < tableSize; u++)
+                {
+                    byte symbol = (byte)(tableDecode[u].symbol);
+                    uint nextState = symbolNext[symbol]++;
+
+                    tableDecode[u].nbBits = (byte)(tableLog - BIT_highbit32(nextState));
+                    tableDecode[u].newState = (ushort)((nextState << (int)(tableDecode[u].nbBits)) - tableSize);
+                }
+            }
+
+            return 0;
+        }
+
+        public static nuint FSE_buildDTable_wksp(uint* dt, short* normalizedCounter, uint maxSymbolValue, uint tableLog, void* workSpace, nuint wkspSize)
+        {
+            return FSE_buildDTable_internal(dt, normalizedCounter, maxSymbolValue, tableLog, workSpace, wkspSize);
+        }
+
+        /*-*******************************************************
+        *  Decompression (Byte symbols)
+        *********************************************************/
+        public static nuint FSE_buildDTable_rle(uint* dt, byte symbolValue)
+        {
+            void* ptr = (void*)dt;
+            FSE_DTableHeader* DTableH = (FSE_DTableHeader*)(ptr);
+            void* dPtr = (void*)(dt + 1);
+            FSE_decode_t* cell = (FSE_decode_t*)(dPtr);
+
+            DTableH->tableLog = 0;
+            DTableH->fastMode = 0;
+            cell->newState = 0;
+            cell->symbol = symbolValue;
+            cell->nbBits = 0;
+            return 0;
+        }
+
+        public static nuint FSE_buildDTable_raw(uint* dt, uint nbBits)
+        {
+            void* ptr = (void*)dt;
+            FSE_DTableHeader* DTableH = (FSE_DTableHeader*)(ptr);
+            void* dPtr = (void*)(dt + 1);
+            FSE_decode_t* dinfo = (FSE_decode_t*)(dPtr);
+            uint tableSize = (uint)(1 << (int)nbBits);
+            uint tableMask = tableSize - 1;
+            uint maxSV1 = tableMask + 1;
+            uint s;
+
+            if (nbBits < 1)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            }
+
+            DTableH->tableLog = (ushort)(nbBits);
+            DTableH->fastMode = 1;
+            for (s = 0; s < maxSV1; s++)
+            {
+                dinfo[s].newState = 0;
+                dinfo[s].symbol = (byte)(s);
+                dinfo[s].nbBits = (byte)(nbBits);
+            }
+
+            return 0;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint FSE_decompress_usingDTable_generic(void* dst, nuint maxDstSize, void* cSrc, nuint cSrcSize, uint* dt, uint fast)
+        {
+            byte* ostart = (byte*)(dst);
+            byte* op = ostart;
+            byte* omax = op + maxDstSize;
+            byte* olimit = omax - 3;
+            BIT_DStream_t bitD;
+            FSE_DState_t state1;
+            FSE_DState_t state2;
+
+
+            {
+                nuint _var_err__ = BIT_initDStream(&bitD, cSrc, cSrcSize);
+
+                if ((ERR_isError(_var_err__)) != 0)
+                {
+                    return _var_err__;
+                }
+            }
+
+            FSE_initDState(&state1, &bitD, dt);
+            FSE_initDState(&state2, &bitD, dt);
+            for (; ((BIT_reloadDStream(&bitD) == BIT_DStream_status.BIT_DStream_unfinished) && (op < olimit)); op += 4)
+            {
+                op[0] = fast != 0 ? FSE_decodeSymbolFast(&state1, &bitD) : FSE_decodeSymbol(&state1, &bitD);
+                if ((uint)((14 - 2) * 2 + 7) > (nuint)(sizeof(nuint)) * 8)
+                {
+                    BIT_reloadDStream(&bitD);
+                }
+
+                op[1] = fast != 0 ? FSE_decodeSymbolFast(&state2, &bitD) : FSE_decodeSymbol(&state2, &bitD);
+                if ((uint)((14 - 2) * 4 + 7) > (nuint)(sizeof(nuint)) * 8)
+                {
+                    if (BIT_reloadDStream(&bitD) > BIT_DStream_status.BIT_DStream_unfinished)
+                    {
+                        op += 2;
+                        break;
+                    }
+                }
+
+                op[2] = fast != 0 ? FSE_decodeSymbolFast(&state1, &bitD) : FSE_decodeSymbol(&state1, &bitD);
+                if ((uint)((14 - 2) * 2 + 7) > (nuint)(sizeof(nuint)) * 8)
+                {
+                    BIT_reloadDStream(&bitD);
+                }
+
+                op[3] = fast != 0 ? FSE_decodeSymbolFast(&state2, &bitD) : FSE_decodeSymbol(&state2, &bitD);
+            }
+
+            while (1 != 0)
+            {
+                if (op > (omax - 2))
+                {
+                    return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+                }
+
+                *op++ = fast != 0 ? FSE_decodeSymbolFast(&state1, &bitD) : FSE_decodeSymbol(&state1, &bitD);
+                if (BIT_reloadDStream(&bitD) == BIT_DStream_status.BIT_DStream_overflow)
+                {
+                    *op++ = fast != 0 ? FSE_decodeSymbolFast(&state2, &bitD) : FSE_decodeSymbol(&state2, &bitD);
+                    break;
+                }
+
+                if (op > (omax - 2))
+                {
+                    return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_dstSize_tooSmall)));
+                }
+
+                *op++ = fast != 0 ? FSE_decodeSymbolFast(&state2, &bitD) : FSE_decodeSymbol(&state2, &bitD);
+                if (BIT_reloadDStream(&bitD) == BIT_DStream_status.BIT_DStream_overflow)
+                {
+                    *op++ = fast != 0 ? FSE_decodeSymbolFast(&state1, &bitD) : FSE_decodeSymbol(&state1, &bitD);
+                    break;
+                }
+            }
+
+            return (nuint)(op - ostart);
+        }
+
+        /*! FSE_decompress_usingDTable():
+            Decompress compressed source `cSrc` of size `cSrcSize` using `dt`
+            into `dst` which must be already allocated.
+            @return : size of regenerated data (necessarily <= `dstCapacity`),
+                      or an errorCode, which can be tested using FSE_isError() */
+        public static nuint FSE_decompress_usingDTable(void* dst, nuint originalSize, void* cSrc, nuint cSrcSize, uint* dt)
+        {
+            void* ptr = (void*)dt;
+            FSE_DTableHeader* DTableH = (FSE_DTableHeader*)(ptr);
+            uint fastMode = DTableH->fastMode;
+
+            if (fastMode != 0)
+            {
+                return FSE_decompress_usingDTable_generic(dst, originalSize, cSrc, cSrcSize, dt, 1);
+            }
+
+            return FSE_decompress_usingDTable_generic(dst, originalSize, cSrc, cSrcSize, dt, 0);
+        }
+
+        public static nuint FSE_decompress_wksp(void* dst, nuint dstCapacity, void* cSrc, nuint cSrcSize, uint maxLog, void* workSpace, nuint wkspSize)
+        {
+            return FSE_decompress_wksp_bmi2(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 0);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static nuint FSE_decompress_wksp_body(void* dst, nuint dstCapacity, void* cSrc, nuint cSrcSize, uint maxLog, void* workSpace, nuint wkspSize, int bmi2)
+        {
+            byte* istart = (byte*)(cSrc);
+            byte* ip = istart;
+            uint tableLog;
+            uint maxSymbolValue = 255;
+            FSE_DecompressWksp* wksp = (FSE_DecompressWksp*)(workSpace);
+
+            if (wkspSize < (nuint)(sizeof(FSE_DecompressWksp)))
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_GENERIC)));
+            }
+
+
+            {
+                nuint NCountLength = FSE_readNCount_bmi2((short*)wksp->ncount, &maxSymbolValue, &tableLog, (void*)istart, cSrcSize, bmi2);
+
+                if ((ERR_isError(NCountLength)) != 0)
+                {
+                    return NCountLength;
+                }
+
+                if (tableLog > maxLog)
+                {
+                    return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+                }
+
+                assert(NCountLength <= cSrcSize);
+                ip += NCountLength;
+                cSrcSize -= NCountLength;
+            }
+
+            if ((((uint)((1 + (1 << (int)(tableLog)))) + ((((nuint)(sizeof(short)) * (maxSymbolValue + 1) + (1UL << (int)tableLog) + 8) + (nuint)(sizeof(uint)) - 1) / (nuint)(sizeof(uint))) + (uint)((255 + 1) / 2) + 1) * (nuint)(sizeof(uint))) > wkspSize)
+            {
+                return (unchecked((nuint)(-(int)ZSTD_ErrorCode.ZSTD_error_tableLog_tooLarge)));
+            }
+
+            workSpace = wksp->dtable + (1 + (1 << (int)(tableLog)));
+            wkspSize -= (nuint)(sizeof(FSE_DecompressWksp)) + ((uint)((1 + (1 << (int)(tableLog)))) * (nuint)(sizeof(uint)));
+
+            {
+                nuint _var_err__ = FSE_buildDTable_internal((uint*)wksp->dtable, (short*)wksp->ncount, maxSymbolValue, tableLog, workSpace, wkspSize);
+
+                if ((ERR_isError(_var_err__)) != 0)
+                {
+                    return _var_err__;
+                }
+            }
+
+
+            {
+                void* ptr = (void*)wksp->dtable;
+                FSE_DTableHeader* DTableH = (FSE_DTableHeader*)(ptr);
+                uint fastMode = DTableH->fastMode;
+
+                if (fastMode != 0)
+                {
+                    return FSE_decompress_usingDTable_generic(dst, dstCapacity, (void*)ip, cSrcSize, (uint*)wksp->dtable, 1);
+                }
+
+                return FSE_decompress_usingDTable_generic(dst, dstCapacity, (void*)ip, cSrcSize, (uint*)wksp->dtable, 0);
+            }
+        }
+
+        /* Avoids the FORCE_INLINE of the _body() function. */
+        private static nuint FSE_decompress_wksp_body_default(void* dst, nuint dstCapacity, void* cSrc, nuint cSrcSize, uint maxLog, void* workSpace, nuint wkspSize)
+        {
+            return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 0);
+        }
+
+        private static nuint FSE_decompress_wksp_body_bmi2(void* dst, nuint dstCapacity, void* cSrc, nuint cSrcSize, uint maxLog, void* workSpace, nuint wkspSize)
+        {
+            return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 1);
+        }
+
+        public static nuint FSE_decompress_wksp_bmi2(void* dst, nuint dstCapacity, void* cSrc, nuint cSrcSize, uint maxLog, void* workSpace, nuint wkspSize, int bmi2)
+        {
+            if (bmi2 != 0)
+            {
+                return FSE_decompress_wksp_body_bmi2(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);
+            }
+
+            return FSE_decompress_wksp_body_default(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);
+        }
+
+        /*! FSE_buildDTable():
+            Builds 'dt', which must be already allocated, using FSE_createDTable().
+            return : 0, or an errorCode, which can be tested using FSE_isError() */
+        public static nuint FSE_buildDTable(uint* dt, short* normalizedCounter, uint maxSymbolValue, uint tableLog)
+        {
+            uint* wksp = stackalloc uint[8322];
+
+            return FSE_buildDTable_wksp(dt, normalizedCounter, maxSymbolValue, tableLog, (void*)wksp, (nuint)(sizeof(uint) * 8322));
+        }
+
+        /*! FSE_decompress():
+            Decompress FSE data from buffer 'cSrc', of size 'cSrcSize',
+            into already allocated destination buffer 'dst', of size 'dstCapacity'.
+            @return : size of regenerated data (<= maxDstSize),
+                      or an error code, which can be tested using FSE_isError() .
+
+            ** Important ** : FSE_decompress() does not decompress non-compressible nor RLE data !!!
+            Why ? : making this distinction requires a header.
+            Header management is intentionally delegated to the user layer, which can better manage special cases.
+        */
+        public static nuint FSE_decompress(void* dst, nuint dstCapacity, void* cSrc, nuint cSrcSize)
+        {
+            uint* wksp = stackalloc uint[5380];
+
+            return FSE_decompress_wksp(dst, dstCapacity, cSrc, cSrcSize, (uint)((14 - 2)), (void*)wksp, (nuint)(sizeof(uint) * 5380));
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/HIST_checkInput_e.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public enum HIST_checkInput_e
+    {
+        trustInput,
+        checkMaxSymbolValue,
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/HUF_CElt_s.cs

@@ -0,0 +1,13 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /* static allocation of HUF's Compression Table */
+    /* this is a private definition, just exposed for allocation and strict aliasing purpose. never EVER access its members directly */
+    public partial struct HUF_CElt_s
+    {
+        public ushort val;
+
+        public byte nbBits;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/HUF_CompressWeightsWksp.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public unsafe partial struct HUF_CompressWeightsWksp
+    {
+        public fixed uint CTable[59];
+
+        public fixed uint scratchBuffer[30];
+
+        public fixed uint count[13];
+
+        public fixed short norm[13];
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/HUF_DEltX1.cs

@@ -0,0 +1,16 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /*-***************************/
+    /*  single-symbol decoding   */
+    /*-***************************/
+    public partial struct HUF_DEltX1
+    {
+        /* single-symbol decoding */
+        public byte @byte;
+
+        /* single-symbol decoding */
+        public byte nbBits;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/HUF_DEltX2.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    /* *************************/
+    /* double-symbols decoding */
+    /* *************************/
+    public partial struct HUF_DEltX2
+    {
+        /* double-symbols decoding */
+        public ushort sequence;
+
+        /* double-symbols decoding */
+        public byte nbBits;
+
+        /* double-symbols decoding */
+        public byte length;
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/HUF_ReadDTableX1_Workspace.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public unsafe partial struct HUF_ReadDTableX1_Workspace
+    {
+        public fixed uint rankVal[16];
+
+        public fixed uint rankStart[16];
+
+        public fixed uint statsWksp[218];
+
+        public fixed byte symbols[256];
+
+        public fixed byte huffWeight[256];
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/HUF_ReadDTableX2_Workspace.cs

@@ -0,0 +1,389 @@
+using InlineIL;
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using static InlineIL.IL.Emit;
+
+namespace ZstdSharp.Unsafe
+{
+    public unsafe partial struct HUF_ReadDTableX2_Workspace
+    {
+        public _rankVal_e__FixedBuffer rankVal;
+
+        public fixed uint rankStats[13];
+
+        public fixed uint rankStart0[14];
+
+        public _sortedSymbol_e__FixedBuffer sortedSymbol;
+
+        public fixed byte weightList[256];
+
+        public fixed uint calleeWksp[218];
+
+        public unsafe partial struct _rankVal_e__FixedBuffer
+        {
+            public rankValCol_t e0;
+            public rankValCol_t e1;
+            public rankValCol_t e2;
+            public rankValCol_t e3;
+            public rankValCol_t e4;
+            public rankValCol_t e5;
+            public rankValCol_t e6;
+            public rankValCol_t e7;
+            public rankValCol_t e8;
+            public rankValCol_t e9;
+            public rankValCol_t e10;
+            public rankValCol_t e11;
+
+            public ref rankValCol_t this[int index]
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                [InlineMethod.Inline]
+                get => ref *(this + (uint)index);
+            }
+
+            public ref rankValCol_t this[uint index]
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                [InlineMethod.Inline]
+                get => ref *(this + index);
+            }
+
+            public ref rankValCol_t this[nuint index]
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                [InlineMethod.Inline]
+                get => ref *(this + (uint)index);
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [InlineMethod.Inline]
+            public static implicit operator rankValCol_t*(in _rankVal_e__FixedBuffer t)
+            {
+                Ldarg_0();
+                Ldflda(new FieldRef(typeof(_rankVal_e__FixedBuffer), nameof(e0)));
+                return IL.ReturnPointer<rankValCol_t>();
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [InlineMethod.Inline]
+            public static rankValCol_t* operator +(in _rankVal_e__FixedBuffer t, uint index)
+            {
+                Ldarg_0();
+                Ldflda(new FieldRef(typeof(_rankVal_e__FixedBuffer), nameof(e0)));
+                Ldarg_1();
+                Conv_I();
+                Sizeof<rankValCol_t>();
+                Conv_I();
+                Mul();
+                Add();
+                return IL.ReturnPointer<rankValCol_t>();
+            }
+        }
+
+        public unsafe partial struct _sortedSymbol_e__FixedBuffer
+        {
+            public sortedSymbol_t e0;
+            public sortedSymbol_t e1;
+            public sortedSymbol_t e2;
+            public sortedSymbol_t e3;
+            public sortedSymbol_t e4;
+            public sortedSymbol_t e5;
+            public sortedSymbol_t e6;
+            public sortedSymbol_t e7;
+            public sortedSymbol_t e8;
+            public sortedSymbol_t e9;
+            public sortedSymbol_t e10;
+            public sortedSymbol_t e11;
+            public sortedSymbol_t e12;
+            public sortedSymbol_t e13;
+            public sortedSymbol_t e14;
+            public sortedSymbol_t e15;
+            public sortedSymbol_t e16;
+            public sortedSymbol_t e17;
+            public sortedSymbol_t e18;
+            public sortedSymbol_t e19;
+            public sortedSymbol_t e20;
+            public sortedSymbol_t e21;
+            public sortedSymbol_t e22;
+            public sortedSymbol_t e23;
+            public sortedSymbol_t e24;
+            public sortedSymbol_t e25;
+            public sortedSymbol_t e26;
+            public sortedSymbol_t e27;
+            public sortedSymbol_t e28;
+            public sortedSymbol_t e29;
+            public sortedSymbol_t e30;
+            public sortedSymbol_t e31;
+            public sortedSymbol_t e32;
+            public sortedSymbol_t e33;
+            public sortedSymbol_t e34;
+            public sortedSymbol_t e35;
+            public sortedSymbol_t e36;
+            public sortedSymbol_t e37;
+            public sortedSymbol_t e38;
+            public sortedSymbol_t e39;
+            public sortedSymbol_t e40;
+            public sortedSymbol_t e41;
+            public sortedSymbol_t e42;
+            public sortedSymbol_t e43;
+            public sortedSymbol_t e44;
+            public sortedSymbol_t e45;
+            public sortedSymbol_t e46;
+            public sortedSymbol_t e47;
+            public sortedSymbol_t e48;
+            public sortedSymbol_t e49;
+            public sortedSymbol_t e50;
+            public sortedSymbol_t e51;
+            public sortedSymbol_t e52;
+            public sortedSymbol_t e53;
+            public sortedSymbol_t e54;
+            public sortedSymbol_t e55;
+            public sortedSymbol_t e56;
+            public sortedSymbol_t e57;
+            public sortedSymbol_t e58;
+            public sortedSymbol_t e59;
+            public sortedSymbol_t e60;
+            public sortedSymbol_t e61;
+            public sortedSymbol_t e62;
+            public sortedSymbol_t e63;
+            public sortedSymbol_t e64;
+            public sortedSymbol_t e65;
+            public sortedSymbol_t e66;
+            public sortedSymbol_t e67;
+            public sortedSymbol_t e68;
+            public sortedSymbol_t e69;
+            public sortedSymbol_t e70;
+            public sortedSymbol_t e71;
+            public sortedSymbol_t e72;
+            public sortedSymbol_t e73;
+            public sortedSymbol_t e74;
+            public sortedSymbol_t e75;
+            public sortedSymbol_t e76;
+            public sortedSymbol_t e77;
+            public sortedSymbol_t e78;
+            public sortedSymbol_t e79;
+            public sortedSymbol_t e80;
+            public sortedSymbol_t e81;
+            public sortedSymbol_t e82;
+            public sortedSymbol_t e83;
+            public sortedSymbol_t e84;
+            public sortedSymbol_t e85;
+            public sortedSymbol_t e86;
+            public sortedSymbol_t e87;
+            public sortedSymbol_t e88;
+            public sortedSymbol_t e89;
+            public sortedSymbol_t e90;
+            public sortedSymbol_t e91;
+            public sortedSymbol_t e92;
+            public sortedSymbol_t e93;
+            public sortedSymbol_t e94;
+            public sortedSymbol_t e95;
+            public sortedSymbol_t e96;
+            public sortedSymbol_t e97;
+            public sortedSymbol_t e98;
+            public sortedSymbol_t e99;
+            public sortedSymbol_t e100;
+            public sortedSymbol_t e101;
+            public sortedSymbol_t e102;
+            public sortedSymbol_t e103;
+            public sortedSymbol_t e104;
+            public sortedSymbol_t e105;
+            public sortedSymbol_t e106;
+            public sortedSymbol_t e107;
+            public sortedSymbol_t e108;
+            public sortedSymbol_t e109;
+            public sortedSymbol_t e110;
+            public sortedSymbol_t e111;
+            public sortedSymbol_t e112;
+            public sortedSymbol_t e113;
+            public sortedSymbol_t e114;
+            public sortedSymbol_t e115;
+            public sortedSymbol_t e116;
+            public sortedSymbol_t e117;
+            public sortedSymbol_t e118;
+            public sortedSymbol_t e119;
+            public sortedSymbol_t e120;
+            public sortedSymbol_t e121;
+            public sortedSymbol_t e122;
+            public sortedSymbol_t e123;
+            public sortedSymbol_t e124;
+            public sortedSymbol_t e125;
+            public sortedSymbol_t e126;
+            public sortedSymbol_t e127;
+            public sortedSymbol_t e128;
+            public sortedSymbol_t e129;
+            public sortedSymbol_t e130;
+            public sortedSymbol_t e131;
+            public sortedSymbol_t e132;
+            public sortedSymbol_t e133;
+            public sortedSymbol_t e134;
+            public sortedSymbol_t e135;
+            public sortedSymbol_t e136;
+            public sortedSymbol_t e137;
+            public sortedSymbol_t e138;
+            public sortedSymbol_t e139;
+            public sortedSymbol_t e140;
+            public sortedSymbol_t e141;
+            public sortedSymbol_t e142;
+            public sortedSymbol_t e143;
+            public sortedSymbol_t e144;
+            public sortedSymbol_t e145;
+            public sortedSymbol_t e146;
+            public sortedSymbol_t e147;
+            public sortedSymbol_t e148;
+            public sortedSymbol_t e149;
+            public sortedSymbol_t e150;
+            public sortedSymbol_t e151;
+            public sortedSymbol_t e152;
+            public sortedSymbol_t e153;
+            public sortedSymbol_t e154;
+            public sortedSymbol_t e155;
+            public sortedSymbol_t e156;
+            public sortedSymbol_t e157;
+            public sortedSymbol_t e158;
+            public sortedSymbol_t e159;
+            public sortedSymbol_t e160;
+            public sortedSymbol_t e161;
+            public sortedSymbol_t e162;
+            public sortedSymbol_t e163;
+            public sortedSymbol_t e164;
+            public sortedSymbol_t e165;
+            public sortedSymbol_t e166;
+            public sortedSymbol_t e167;
+            public sortedSymbol_t e168;
+            public sortedSymbol_t e169;
+            public sortedSymbol_t e170;
+            public sortedSymbol_t e171;
+            public sortedSymbol_t e172;
+            public sortedSymbol_t e173;
+            public sortedSymbol_t e174;
+            public sortedSymbol_t e175;
+            public sortedSymbol_t e176;
+            public sortedSymbol_t e177;
+            public sortedSymbol_t e178;
+            public sortedSymbol_t e179;
+            public sortedSymbol_t e180;
+            public sortedSymbol_t e181;
+            public sortedSymbol_t e182;
+            public sortedSymbol_t e183;
+            public sortedSymbol_t e184;
+            public sortedSymbol_t e185;
+            public sortedSymbol_t e186;
+            public sortedSymbol_t e187;
+            public sortedSymbol_t e188;
+            public sortedSymbol_t e189;
+            public sortedSymbol_t e190;
+            public sortedSymbol_t e191;
+            public sortedSymbol_t e192;
+            public sortedSymbol_t e193;
+            public sortedSymbol_t e194;
+            public sortedSymbol_t e195;
+            public sortedSymbol_t e196;
+            public sortedSymbol_t e197;
+            public sortedSymbol_t e198;
+            public sortedSymbol_t e199;
+            public sortedSymbol_t e200;
+            public sortedSymbol_t e201;
+            public sortedSymbol_t e202;
+            public sortedSymbol_t e203;
+            public sortedSymbol_t e204;
+            public sortedSymbol_t e205;
+            public sortedSymbol_t e206;
+            public sortedSymbol_t e207;
+            public sortedSymbol_t e208;
+            public sortedSymbol_t e209;
+            public sortedSymbol_t e210;
+            public sortedSymbol_t e211;
+            public sortedSymbol_t e212;
+            public sortedSymbol_t e213;
+            public sortedSymbol_t e214;
+            public sortedSymbol_t e215;
+            public sortedSymbol_t e216;
+            public sortedSymbol_t e217;
+            public sortedSymbol_t e218;
+            public sortedSymbol_t e219;
+            public sortedSymbol_t e220;
+            public sortedSymbol_t e221;
+            public sortedSymbol_t e222;
+            public sortedSymbol_t e223;
+            public sortedSymbol_t e224;
+            public sortedSymbol_t e225;
+            public sortedSymbol_t e226;
+            public sortedSymbol_t e227;
+            public sortedSymbol_t e228;
+            public sortedSymbol_t e229;
+            public sortedSymbol_t e230;
+            public sortedSymbol_t e231;
+            public sortedSymbol_t e232;
+            public sortedSymbol_t e233;
+            public sortedSymbol_t e234;
+            public sortedSymbol_t e235;
+            public sortedSymbol_t e236;
+            public sortedSymbol_t e237;
+            public sortedSymbol_t e238;
+            public sortedSymbol_t e239;
+            public sortedSymbol_t e240;
+            public sortedSymbol_t e241;
+            public sortedSymbol_t e242;
+            public sortedSymbol_t e243;
+            public sortedSymbol_t e244;
+            public sortedSymbol_t e245;
+            public sortedSymbol_t e246;
+            public sortedSymbol_t e247;
+            public sortedSymbol_t e248;
+            public sortedSymbol_t e249;
+            public sortedSymbol_t e250;
+            public sortedSymbol_t e251;
+            public sortedSymbol_t e252;
+            public sortedSymbol_t e253;
+            public sortedSymbol_t e254;
+            public sortedSymbol_t e255;
+
+            public ref sortedSymbol_t this[int index]
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                [InlineMethod.Inline]
+                get => ref *(this + (uint)index);
+            }
+
+            public ref sortedSymbol_t this[uint index]
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                [InlineMethod.Inline]
+                get => ref *(this + index);
+            }
+
+            public ref sortedSymbol_t this[nuint index]
+            {
+                [MethodImpl(MethodImplOptions.AggressiveInlining)]
+                [InlineMethod.Inline]
+                get => ref *(this + (uint)index);
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [InlineMethod.Inline]
+            public static implicit operator sortedSymbol_t*(in _sortedSymbol_e__FixedBuffer t)
+            {
+                Ldarg_0();
+                Ldflda(new FieldRef(typeof(_sortedSymbol_e__FixedBuffer), nameof(e0)));
+                return IL.ReturnPointer<sortedSymbol_t>();
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [InlineMethod.Inline]
+            public static sortedSymbol_t* operator +(in _sortedSymbol_e__FixedBuffer t, uint index)
+            {
+                Ldarg_0();
+                Ldflda(new FieldRef(typeof(_sortedSymbol_e__FixedBuffer), nameof(e0)));
+                Ldarg_1();
+                Conv_I();
+                Sizeof<sortedSymbol_t>();
+                Conv_I();
+                Mul();
+                Add();
+                return IL.ReturnPointer<sortedSymbol_t>();
+            }
+        }
+    }
+}

src/SharpCompress/Compressors/Zstd/Unsafe/HUF_WriteCTableWksp.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace ZstdSharp.Unsafe
+{
+    public unsafe partial struct HUF_WriteCTableWksp
+    {
+        public HUF_CompressWeightsWksp wksp;
+
+        /* precomputed conversion table */
+        public fixed byte bitsToWeight[13];
+
+        public fixed byte huffWeight[255];
+    }
+}