Mark for 0.32

XZ decoding BCJ filters support

.config/dotnet-tools.json

@@ -0,0 +1,12 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "dotnet-format": {
+      "version": "4.1.131201",
+      "commands": [
+        "dotnet-format"
+      ]
+    }
+  }
+}

.editorconfig

@@ -0,0 +1,543 @@
+# 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

@@ -0,0 +1,6 @@
+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

@@ -9,16 +9,12 @@ jobs:
         os: [windows-latest, ubuntu-latest]
 
     steps:
-    - uses: actions/checkout@v1
-    - uses: actions/setup-dotnet@v1
+    - uses: actions/checkout@v3
+    - uses: actions/setup-dotnet@v2
       with:
-        dotnet-version: 3.1.302
+        dotnet-version: 6.0.x
     - run: dotnet run -p build/build.csproj
-    - uses: actions/upload-artifact@v2
+    - uses: actions/upload-artifact@v3
       with:
         name: ${{ matrix.os }}-sharpcompress.nupkg
         path: artifacts/*
-    - uses: actions/upload-artifact@v2
-      with:
-        name: ${{ matrix.os }}-sharpcompress.snupkg
-        path: artifacts/*

.gitignore

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

FORMATS.md

@@ -19,7 +19,6 @@
 | Tar.XZ                 | LZMA2                                             | Decompress          | TarArchive      | TarReader  | TarWriter (3) |
 | GZip (single file)     | DEFLATE                                           | Both                | GZipArchive     | GZipReader | GZipWriter    |
 | 7Zip (4)               | LZMA, LZMA2, BZip2, PPMd, BCJ, BCJ2, Deflate      | Decompress          | SevenZipArchive | N/A        | N/A           |
-| LZip (single file) (5) | LZip (LZMA)                                       | Both                | LZipArchive     | LZipReader | LZipWriter    |
 
 1. SOLID Rars are only supported in the RarReader API.
 2. Zip format supports pkware and WinzipAES encryption. However, encrypted LZMA is not supported. Zip64 reading/writing is supported but only with seekable streams as the Zip spec doesn't support Zip64 data in post data descriptors. Deflate64 is only supported for reading.

README.md

@@ -1,6 +1,6 @@
 # SharpCompress
 
-SharpCompress is a compression library in pure C# for .NET Standard 2.0, 2.1 and NET 4.6 that can unrar, un7zip, unzip, untar unbzip2, ungzip, unlzip with forward-only reading and file random access APIs. Write support for zip/tar/bzip2/gzip/lzip are implemented.
+SharpCompress is a compression library in pure C# for .NET Standard 2.0, 2.1, .NET Core 3.1 and .NET 5.0 that can unrar, un7zip, unzip, untar unbzip2, ungzip, unlzip with forward-only reading and file random access APIs. Write support for zip/tar/bzip2/gzip/lzip are implemented.
 
 The major feature is support for non-seekable streams so large files can be processed on the fly (i.e. download stream).
 
@@ -182,6 +182,8 @@ 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

@@ -6,71 +6,78 @@ using GlobExpressions;
 using static Bullseye.Targets;
 using static SimpleExec.Command;
 
-class Program
-{
-    private const string Clean = "clean";
-    private const string Build = "build";
-    private const string Test = "test";
-    private const string Publish = "publish";
-    
-    static void Main(string[] args)
-    {
-        Target(Clean,
-            ForEach("**/bin", "**/obj"),
-            dir =>
-            {
-                IEnumerable<string> GetDirectories(string d)
-                {
-                    return Glob.Directories(".", d);
-                }
+const string Clean = "clean";
+const string Format = "format";
+const string Build = "build";
+const string Test = "test";
+const string Publish = "publish";
 
-                void RemoveDirectory(string d)
-                {
-                    if (Directory.Exists(d))
-                    {
-                        Console.WriteLine(d);
-                        Directory.Delete(d, true);
-                    }
-                }
+Target(Clean,
+       ForEach("**/bin", "**/obj"),
+       dir =>
+       {
+           IEnumerable<string> GetDirectories(string d)
+           {
+               return Glob.Directories(".", d);
+           }
 
-                foreach (var d in GetDirectories(dir))
-                {
-                    RemoveDirectory(d);
-                }
-            });
-
-        Target(Build, ForEach("net46", "netstandard2.0", "netstandard2.1"), 
-               framework =>
+           void RemoveDirectory(string d)
+           {
+               if (Directory.Exists(d))
                {
-                    if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && framework == "net46")
-                    {
-                        return;
-                    }
-                    Run("dotnet", "build src/SharpCompress/SharpCompress.csproj -c Release");
-                });
+                   Console.WriteLine(d);
+                   Directory.Delete(d, true);
+               }
+           }
 
-        Target(Test, DependsOn(Build), ForEach("netcoreapp3.1"), 
-            framework =>
-            {
-                IEnumerable<string> GetFiles(string d)
-                {
-                    return Glob.Files(".", d);
-                }
+           foreach (var d in GetDirectories(dir))
+           {
+               RemoveDirectory(d);
+           }
+       });
 
-                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(Format,
+       () =>
+       {
+           Run("dotnet", "tool restore");
+           Run("dotnet", "format --check");
+       });
 
-        Target("default", DependsOn(Publish), () => Console.WriteLine("Done!"));
-        
-        RunTargetsAndExit(args);
-    }
-}
+Target(Build,
+       DependsOn(Format),
+       framework =>
+       {
+           Run("dotnet", "build src/SharpCompress/SharpCompress.csproj -c Release");
+       });
+
+Target(Test,
+       DependsOn(Build),
+       ForEach("net6.0", "net461"),
+       framework =>
+       {
+           IEnumerable<string> GetFiles(string d)
+           {
+               return Glob.Files(".", d);
+           }
+
+           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);

build/build.csproj

@@ -2,13 +2,13 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Bullseye" Version="3.3.0" />
-    <PackageReference Include="Glob" Version="1.1.7" />
-    <PackageReference Include="SimpleExec" Version="6.2.0" />
+    <PackageReference Include="Bullseye" Version="4.0.0" />
+    <PackageReference Include="Glob" Version="1.1.9" />
+    <PackageReference Include="SimpleExec" Version="10.0.0" />
   </ItemGroup>
 
 </Project>

global.json

@@ -1,5 +1,6 @@
 {
   "sdk": {
-    "version": "3.1.302"
+    "version": "6.0.200",
+    "rollForward": "latestFeature"
   }
 }

src/SharpCompress/Algorithms/Adler32.cs

@@ -0,0 +1,420 @@
+// 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/Archives/AbstractArchive.cs

@@ -1,8 +1,9 @@
-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
@@ -23,28 +24,14 @@ namespace SharpCompress.Archives
         protected ReaderOptions ReaderOptions { get; }
 
         private bool disposed;
+        protected SourceStream SrcStream;
 
-        internal AbstractArchive(ArchiveType type, FileInfo fileInfo, ReaderOptions readerOptions)
+        internal AbstractArchive(ArchiveType type, SourceStream srcStream)
         {
             Type = type;
-            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)));
+            ReaderOptions = srcStream.ReaderOptions;
+            SrcStream = srcStream;
+            lazyVolumes = new LazyReadOnlyCollection<TVolume>(LoadVolumes(SrcStream));
             lazyEntries = new LazyReadOnlyCollection<TEntry>(LoadEntries(Volumes));
         }
 
@@ -81,29 +68,29 @@ namespace SharpCompress.Archives
         /// <summary>
         /// Returns an ReadOnlyCollection of all the RarArchiveEntries across the one or many parts of the RarArchive.
         /// </summary>
-        public virtual ICollection<TEntry> Entries { get { return lazyEntries; } }
+        public virtual ICollection<TEntry> Entries => lazyEntries;
 
         /// <summary>
         /// Returns an ReadOnlyCollection of all the RarArchiveVolumes across the one or many parts of the RarArchive.
         /// </summary>
-        public ICollection<TVolume> Volumes { get { return lazyVolumes; } }
+        public ICollection<TVolume> Volumes => lazyVolumes;
 
         /// <summary>
         /// The total size of the files compressed in the archive.
         /// </summary>
-        public virtual long TotalSize { get { return Entries.Aggregate(0L, (total, cf) => total + cf.CompressedSize); } }
+        public virtual long TotalSize => Entries.Aggregate(0L, (total, cf) => total + cf.CompressedSize);
 
         /// <summary>
         /// The total size of the files as uncompressed in the archive.
         /// </summary>
-        public virtual long TotalUncompressSize { get { return Entries.Aggregate(0L, (total, cf) => total + cf.Size); } }
+        public virtual long TotalUncompressSize => Entries.Aggregate(0L, (total, cf) => total + cf.Size);
 
-        protected abstract IEnumerable<TVolume> LoadVolumes(IEnumerable<Stream> streams);
+        protected abstract IEnumerable<TVolume> LoadVolumes(SourceStream srcStream);
         protected abstract IEnumerable<TEntry> LoadEntries(IEnumerable<TVolume> volumes);
 
-        IEnumerable<IArchiveEntry> IArchive.Entries { get { return Entries.Cast<IArchiveEntry>(); } }
+        IEnumerable<IArchiveEntry> IArchive.Entries => Entries.Cast<IArchiveEntry>();
 
-        IEnumerable<IVolume> IArchive.Volumes { get { return lazyVolumes.Cast<IVolume>(); } }
+        IEnumerable<IVolume> IArchive.Volumes => lazyVolumes.Cast<IVolume>();
 
         public virtual void Dispose()
         {
@@ -111,6 +98,8 @@ namespace SharpCompress.Archives
             {
                 lazyVolumes.ForEach(v => v.Dispose());
                 lazyEntries.GetLoaded().Cast<Entry>().ForEach(x => x.Close());
+                if (SrcStream != null)
+                    SrcStream.Dispose();
                 disposed = true;
             }
         }
@@ -132,9 +121,9 @@ namespace SharpCompress.Archives
         void IExtractionListener.FireFilePartExtractionBegin(string name, long size, long compressedSize)
         {
             FilePartExtractionBegin?.Invoke(this, new FilePartExtractionBeginEventArgs(
-                compressedSize : compressedSize,
-                size           : size,
-                name           : name
+                compressedSize: compressedSize,
+                size: size,
+                name: name
             ));
         }
 
@@ -160,7 +149,7 @@ namespace SharpCompress.Archives
         /// <summary>
         /// Archive is SOLID (this means the Archive saved bytes by reusing information which helps for archives containing many small files).
         /// </summary>
-        public virtual bool IsSolid { get { return false; } }
+        public virtual bool IsSolid => false;
 
         /// <summary>
         /// The archive can find all the parts of the archive needed to fully extract the archive.  This forces the parsing of the entire archive.

src/SharpCompress/Archives/AbstractWritableArchive.cs

@@ -1,8 +1,9 @@
-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;
 
@@ -12,24 +13,36 @@ namespace SharpCompress.Archives
         where TEntry : IArchiveEntry
         where TVolume : IVolume
     {
+        private class RebuildPauseDisposable : IDisposable
+        {
+            private readonly AbstractWritableArchive<TEntry, TVolume> archive;
+
+            public RebuildPauseDisposable(AbstractWritableArchive<TEntry, TVolume> archive)
+            {
+                this.archive = archive;
+                archive.pauseRebuilding = true;
+            }
+
+            public void Dispose()
+            {
+                archive.pauseRebuilding = false;
+                archive.RebuildModifiedCollection();
+            }
+        }
         private readonly List<TEntry> newEntries = new List<TEntry>();
         private readonly List<TEntry> removedEntries = new List<TEntry>();
 
         private readonly List<TEntry> modifiedEntries = new List<TEntry>();
         private bool hasModifications;
+        private bool pauseRebuilding;
 
         internal AbstractWritableArchive(ArchiveType type)
             : base(type)
         {
         }
 
-        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)
+        internal AbstractWritableArchive(ArchiveType type, SourceStream srcStream)
+            : base(type, srcStream)
         {
         }
 
@@ -45,8 +58,17 @@ namespace SharpCompress.Archives
             }
         }
 
+        public IDisposable PauseEntryRebuilding()
+        {
+            return new RebuildPauseDisposable(this);
+        }
+
         private void RebuildModifiedCollection()
         {
+            if (pauseRebuilding)
+            {
+                return;
+            }
             hasModifications = true;
             newEntries.RemoveAll(v => removedEntries.Contains(v));
             modifiedEntries.Clear();
@@ -83,8 +105,7 @@ namespace SharpCompress.Archives
         public TEntry AddEntry(string key, Stream source, bool closeStream,
                                long size = 0, DateTime? modified = null)
         {
-            if (key.StartsWith("/")
-                || key.StartsWith("\\"))
+            if (key.Length > 0 && key[0] is '/' or '\\')
             {
                 key = key.Substring(1);
             }
@@ -103,7 +124,7 @@ namespace SharpCompress.Archives
             foreach (var path in Entries.Select(x => x.Key))
             {
                 var p = path.Replace('/', '\\');
-                if (p.StartsWith("\\"))
+                if (p.Length > 0 && p[0] == '\\')
                 {
                     p = p.Substring(1);
                 }

src/SharpCompress/Archives/ArchiveFactory.cs

@@ -1,16 +1,19 @@
-using System;
+using System;
+using System.Collections.Generic;
 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
 {
-    public class ArchiveFactory
+    public static class ArchiveFactory
     {
         /// <summary>
         /// Opens an Archive for random access
@@ -25,60 +28,39 @@ namespace SharpCompress.Archives
             {
                 throw new ArgumentException("Stream should be readable and seekable");
             }
-            readerOptions = readerOptions ?? new ReaderOptions();
-            if (ZipArchive.IsZipFile(stream, null))
+            readerOptions ??= new ReaderOptions();
+
+            ArchiveType? type;
+            IsArchive(stream, out type); //test and reset stream position
+
+            if (type != null)
             {
-                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);
+                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);
+                }
             }
             throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip, LZip");
         }
 
         public static IWritableArchive Create(ArchiveType type)
         {
-            switch (type)
+            return type switch
             {
-                case ArchiveType.Zip:
-                {
-                    return ZipArchive.Create();
-                }
-                case ArchiveType.Tar:
-                {
-                    return TarArchive.Create();
-                }
-                case ArchiveType.GZip:
-                {
-                    return GZipArchive.Create();
-                }
-                default:
-                {
-                    throw new NotSupportedException("Cannot create Archives of type: " + type);
-                }
-            }
+                ArchiveType.Zip => ZipArchive.Create(),
+                ArchiveType.Tar => TarArchive.Create(),
+                ArchiveType.GZip => GZipArchive.Create(),
+                _ => throw new NotSupportedException("Cannot create Archives of type: " + type)
+            };
         }
 
         /// <summary>
@@ -100,35 +82,112 @@ namespace SharpCompress.Archives
         public static IArchive Open(FileInfo fileInfo, ReaderOptions? options = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            options = options ?? new ReaderOptions { LeaveStreamOpen = false };
-            using (var stream = fileInfo.OpenRead())
+            options ??= new ReaderOptions { LeaveStreamOpen = false };
+
+            ArchiveType? type;
+            using (Stream stream = fileInfo.OpenRead())
             {
-                if (ZipArchive.IsZipFile(stream, null))
+                IsArchive(stream, out type); //test and reset stream position
+
+                if (type != null)
                 {
-                    return ZipArchive.Open(fileInfo, options);
+                    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);
+                    }
                 }
-                stream.Seek(0, SeekOrigin.Begin);
-                if (SevenZipArchive.IsSevenZipFile(stream))
-                {
-                    return SevenZipArchive.Open(fileInfo, options);
-                }
-                stream.Seek(0, SeekOrigin.Begin);
-                if (GZipArchive.IsGZipFile(stream))
-                {
-                    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");
             }
+            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)
+            {
+                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);
+                }
+            }
+            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)
+            {
+                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);
+                }
+            }
+            throw new InvalidOperationException("Cannot determine compressed stream type. Supported Archive Formats: Zip, GZip, Tar, Rar, 7Zip");
         }
 
         /// <summary>
@@ -137,12 +196,100 @@ namespace SharpCompress.Archives
         public static void WriteToDirectory(string sourceArchive, string destinationDirectory,
                                             ExtractionOptions? options = null)
         {
-            using (IArchive archive = Open(sourceArchive))
+            using IArchive archive = Open(sourceArchive);
+            foreach (IArchiveEntry entry in archive.Entries)
             {
-                foreach (IArchiveEntry entry in archive.Entries)
-                {
-                    entry.WriteToDirectory(destinationDirectory, options);
-                }
+                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

@@ -0,0 +1,29 @@
+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

@@ -1,9 +1,10 @@
-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;
@@ -32,7 +33,31 @@ namespace SharpCompress.Archives.GZip
         public static GZipArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            return new GZipArchive(fileInfo, readerOptions ?? new ReaderOptions());
+            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()));
         }
 
         /// <summary>
@@ -43,7 +68,7 @@ namespace SharpCompress.Archives.GZip
         public static GZipArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
-            return new GZipArchive(stream, readerOptions ?? new ReaderOptions());
+            return new GZipArchive(new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions()));
         }
 
         public static GZipArchive Create()
@@ -52,20 +77,20 @@ namespace SharpCompress.Archives.GZip
         }
 
         /// <summary>
-        /// Constructor with a FileInfo object to an existing file.
+        /// Constructor with a SourceStream able to handle FileInfo and Streams.
         /// </summary>
-        /// <param name="fileInfo"></param>
+        /// <param name="srcStream"></param>
         /// <param name="options"></param>
-        internal GZipArchive(FileInfo fileInfo, ReaderOptions options)
-            : base(ArchiveType.GZip, fileInfo, options)
+        internal GZipArchive(SourceStream srcStream)
+            : base(ArchiveType.Tar, srcStream)
         {
         }
 
-        protected override IEnumerable<GZipVolume> LoadVolumes(FileInfo file)
+        protected override IEnumerable<GZipVolume> LoadVolumes(SourceStream srcStream)
         {
-            return new GZipVolume(file, ReaderOptions).AsEnumerable();
+            srcStream.LoadAllParts();
+            return srcStream.Streams.Select(a => new GZipVolume(a, ReaderOptions));
         }
-
         public static bool IsGZipFile(string filePath)
         {
             return IsGZipFile(new FileInfo(filePath));
@@ -77,10 +102,9 @@ namespace SharpCompress.Archives.GZip
             {
                 return false;
             }
-            using (Stream stream = fileInfo.OpenRead())
-            {
-                return IsGZipFile(stream);
-            }
+
+            using Stream stream = fileInfo.OpenRead();
+            return IsGZipFile(stream);
         }
 
         public void SaveTo(string filePath)
@@ -99,7 +123,7 @@ namespace SharpCompress.Archives.GZip
         public static bool IsGZipFile(Stream stream)
         {
             // read the header on the first read
-            byte[] header = new byte[10];
+            Span<byte> header = stackalloc byte[10];
 
             // workitem 8501: handle edge case (decompress empty stream)
             if (!stream.ReadFully(header))
@@ -115,16 +139,6 @@ 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)
         {
@@ -161,11 +175,6 @@ 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/IArchiveEntryExtensions.cs

@@ -31,7 +31,7 @@ namespace SharpCompress.Archives
             }
             streamListener.FireEntryExtractionEnd(archiveEntry);
         }
-        
+
         /// <summary>
         /// Extract to specific directory, retaining filename
         /// </summary>
@@ -45,11 +45,11 @@ namespace SharpCompress.Archives
         /// <summary>
         /// Extract to specific file
         /// </summary>
-        public static void WriteToFile(this IArchiveEntry entry, 
+        public static void WriteToFile(this IArchiveEntry entry,
                                        string destinationFileName,
                                        ExtractionOptions? options = null)
         {
-            
+
             ExtractionMethods.WriteEntryToFile(entry, destinationFileName, options,
                                                (x, fm) =>
                                                {

src/SharpCompress/Archives/IWritableArchive.cs

@@ -11,5 +11,11 @@ namespace SharpCompress.Archives
         IArchiveEntry AddEntry(string key, Stream source, bool closeStream, long size = 0, DateTime? modified = null);
 
         void SaveTo(Stream stream, WriterOptions options);
+
+        /// <summary>
+        /// Use this to pause entry rebuilding when adding large collections of entries.  Dispose when complete.  A  using statement is recommended.
+        /// </summary>
+        /// <returns>IDisposeable to resume entry rebuilding</returns>
+        IDisposable PauseEntryRebuilding();
     }
 }

src/SharpCompress/Archives/IWritableArchiveExtensions.cs

@@ -35,11 +35,14 @@ namespace SharpCompress.Archives
             this IWritableArchive writableArchive,
             string filePath, string searchPattern = "*.*", SearchOption searchOption = SearchOption.AllDirectories)
         {
-            foreach (var path in Directory.EnumerateFiles(filePath, searchPattern, searchOption))
+            using (writableArchive.PauseEntryRebuilding())
             {
-                var fileInfo = new FileInfo(path);
-                writableArchive.AddEntry(path.Substring(filePath.Length), fileInfo.OpenRead(), true, fileInfo.Length,
-                                         fileInfo.LastWriteTime);
+                foreach (var path in Directory.EnumerateFiles(filePath, searchPattern, searchOption))
+                {
+                    var fileInfo = new FileInfo(path);
+                    writableArchive.AddEntry(path.Substring(filePath.Length), fileInfo.OpenRead(), true, fileInfo.Length,
+                                            fileInfo.LastWriteTime);
+                }
             }
         }
         public static IArchiveEntry AddEntry(this IWritableArchive writableArchive, string key, FileInfo fileInfo)

src/SharpCompress/Archives/Rar/RarArchive.cs

@@ -5,49 +5,48 @@ 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;
 
 namespace SharpCompress.Archives.Rar
 {
-    public class RarArchive : AbstractArchive<RarArchiveEntry, RarVolume>
+    public class
+        RarArchive : AbstractArchive<RarArchiveEntry, RarVolume>
     {
         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>
-        /// Takes multiple seekable Streams for a multi-part archive
+        /// Constructor with a SourceStream able to handle FileInfo and Streams.
         /// </summary>
-        /// <param name="streams"></param>
+        /// <param name="srcStream"></param>
         /// <param name="options"></param>
-        internal RarArchive(IEnumerable<Stream> streams, ReaderOptions options)
-            : base(ArchiveType.Rar, streams, options)
+        internal RarArchive(SourceStream srcStream)
+            : base(ArchiveType.Rar, srcStream)
         {
         }
 
         protected override IEnumerable<RarArchiveEntry> LoadEntries(IEnumerable<RarVolume> volumes)
         {
-            return RarArchiveEntryFactory.GetEntries(this, volumes);
+            return RarArchiveEntryFactory.GetEntries(this, volumes, ReaderOptions);
         }
 
-        protected override IEnumerable<RarVolume> LoadVolumes(IEnumerable<Stream> streams)
+        protected override IEnumerable<RarVolume> LoadVolumes(SourceStream srcStream)
         {
-            return RarArchiveVolumeFactory.GetParts(streams, ReaderOptions);
+            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();
         }
 
         protected override IReader CreateReaderForSolidExtraction()
@@ -68,7 +67,8 @@ namespace SharpCompress.Archives.Rar
         public static RarArchive Open(string filePath, ReaderOptions? options = null)
         {
             filePath.CheckNotNullOrEmpty(nameof(filePath));
-            return new RarArchive(new FileInfo(filePath), options ?? new ReaderOptions());
+            FileInfo fileInfo = new FileInfo(filePath);
+            return new RarArchive(new SourceStream(fileInfo, i => RarArchiveVolumeFactory.GetFilePart(i, fileInfo), options ?? new ReaderOptions()));
         }
 
         /// <summary>
@@ -79,7 +79,7 @@ namespace SharpCompress.Archives.Rar
         public static RarArchive Open(FileInfo fileInfo, ReaderOptions? options = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            return new RarArchive(fileInfo, options ?? new ReaderOptions());
+            return new RarArchive(new SourceStream(fileInfo, i => RarArchiveVolumeFactory.GetFilePart(i, fileInfo), options ?? new ReaderOptions()));
         }
 
         /// <summary>
@@ -90,20 +90,34 @@ namespace SharpCompress.Archives.Rar
         public static RarArchive Open(Stream stream, ReaderOptions? options = null)
         {
             stream.CheckNotNull(nameof(stream));
-            return Open(stream.AsEnumerable(), options ?? new ReaderOptions());
+            return new RarArchive(new SourceStream(stream, i => null, options ?? new ReaderOptions()));
         }
 
         /// <summary>
-        /// Takes multiple seekable Streams for a multi-part archive
+        /// 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
         /// </summary>
         /// <param name="streams"></param>
-        /// <param name="options"></param>
-        public static RarArchive Open(IEnumerable<Stream> streams, ReaderOptions? options = null)
+        /// <param name="readerOptions"></param>
+        public static RarArchive Open(IEnumerable<Stream> streams, ReaderOptions? readerOptions = null)
         {
             streams.CheckNotNull(nameof(streams));
-            return new RarArchive(streams, options ?? new ReaderOptions());
+            Stream[] strms = streams.ToArray();
+            return new RarArchive(new SourceStream(strms[0], i => i < strms.Length ? strms[i] : null, readerOptions ?? new ReaderOptions()));
         }
 
+
         public static bool IsRarFile(string filePath)
         {
             return IsRarFile(new FileInfo(filePath));
@@ -120,7 +134,7 @@ namespace SharpCompress.Archives.Rar
                 return IsRarFile(stream);
             }
         }
-        
+
         public static bool IsRarFile(Stream stream, ReaderOptions? options = null)
         {
             try

src/SharpCompress/Archives/Rar/RarArchiveEntry.cs

@@ -6,6 +6,7 @@ using SharpCompress.Common;
 using SharpCompress.Common.Rar;
 using SharpCompress.Common.Rar.Headers;
 using SharpCompress.Compressors.Rar;
+using SharpCompress.Readers;
 
 namespace SharpCompress.Archives.Rar
 {
@@ -13,11 +14,14 @@ namespace SharpCompress.Archives.Rar
     {
         private readonly ICollection<RarFilePart> parts;
         private readonly RarArchive archive;
+        private readonly ReaderOptions readerOptions;
 
-        internal RarArchiveEntry(RarArchive archive, IEnumerable<RarFilePart> parts)
+        internal RarArchiveEntry(RarArchive archive, IEnumerable<RarFilePart> parts, ReaderOptions readerOptions)
         {
             this.parts = parts.ToList();
             this.archive = archive;
+            this.readerOptions = readerOptions;
+            this.IsSolid = this.FileHeader.IsSolid;
         }
 
         public override CompressionType CompressionType => CompressionType.Rar;
@@ -61,21 +65,22 @@ namespace SharpCompress.Archives.Rar
             {
                 return new RarStream(archive.UnpackV1.Value, FileHeader, new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>(), archive));
             }
-            
+
             return new RarStream(archive.UnpackV2017.Value, FileHeader, new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>(), archive));
         }
 
-        public bool IsComplete 
-        { 
-            get 
-            { 
-                return parts.Select(fp => fp.FileHeader).Any(fh => !fh.IsSplitAfter); 
-            } 
+        public bool IsComplete
+        {
+            get
+            {
+                var headers = parts.Select(x => x.FileHeader);
+                return !headers.First().IsSplitBefore && !headers.Last().IsSplitAfter;
+            }
         }
 
         private void CheckIncomplete()
         {
-            if (!IsComplete)
+            if (!readerOptions.DisableCheckIncomplete && !IsComplete)
             {
                 throw new IncompleteArchiveException("ArchiveEntry is incomplete and cannot perform this operation.");
             }

src/SharpCompress/Archives/Rar/RarArchiveEntryFactory.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using SharpCompress.Common.Rar;
+using SharpCompress.Readers;
 
 namespace SharpCompress.Archives.Rar
 {
@@ -36,11 +37,12 @@ namespace SharpCompress.Archives.Rar
         }
 
         internal static IEnumerable<RarArchiveEntry> GetEntries(RarArchive archive,
-                                                                IEnumerable<RarVolume> rarParts)
+                                                                IEnumerable<RarVolume> rarParts,
+                                                                ReaderOptions readerOptions)
         {
             foreach (var groupedParts in GetMatchedFileParts(rarParts))
             {
-                yield return new RarArchiveEntry(archive, groupedParts);
+                yield return new RarArchiveEntry(archive, groupedParts, readerOptions);
             }
         }
     }

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;
@@ -6,137 +6,35 @@ 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 IEnumerable<RarVolume> GetParts(IEnumerable<Stream> streams, ReaderOptions options)
+        internal static FileInfo? GetFilePart(int index, FileInfo part1) //base the name on the first part
         {
-            foreach (Stream s in streams)
-            {
-                if (!s.CanRead || !s.CanSeek)
-                {
-                    throw new ArgumentException("Stream is not readable and seekable");
-                }
-                StreamRarArchiveVolume part = new StreamRarArchiveVolume(s, options);
-                yield return part;
-            }
-        }
-        
-        internal static IEnumerable<RarVolume> GetParts(FileInfo fileInfo, ReaderOptions options)
-        {
-            FileInfoRarArchiveVolume part = new FileInfoRarArchiveVolume(fileInfo, options);
-            yield return part;
+            FileInfo? item = null;
 
-            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);
-            }
+            //new style rar - ..part1 | /part01 | part001 ....
+            Match m = Regex.Match(part1.Name, @"^(.*\.part)([0-9]+)(\.rar)$", RegexOptions.IgnoreCase);
+            if (m.Success)
+                item = new FileInfo(Path.Combine(part1.DirectoryName!, String.Concat(m.Groups[1].Value, (index + 1).ToString().PadLeft(m.Groups[2].Value.Length, '0'), m.Groups[3].Value)));
             else
             {
-                return FindNextFileWithNewNumbering(currentFilePart.FileInfo);
+                //old style - ...rar, .r00, .r01 ...
+                m = Regex.Match(part1.Name, @"^(.*\.r)(ar|[0-9]+)$", 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 (item != null && item.Exists)
+                return item;
+
+            return null; //no more items
         }
 
-        private static FileInfo FindNextFileWithOldNumbering(FileInfo currentFileInfo)
-        {
-            // .rar, .r00, .r01, ...
-            string extension = currentFileInfo.Extension;
-
-            StringBuilder 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
-            {
-                int num = 0;
-                if (int.TryParse(extension.Substring(2, 2), out 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);
-            int num = 0;
-            string numString = currentFileInfo.FullName.Substring(startIndex + 5,
-                                                                  currentFileInfo.FullName.IndexOf('.', startIndex + 5) -
-                                                                  startIndex - 5);
-            buffer.Append(".part");
-            if (int.TryParse(numString, out 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;
@@ -34,8 +34,33 @@ namespace SharpCompress.Archives.SevenZip
         public static SevenZipArchive Open(FileInfo fileInfo, ReaderOptions readerOptions = null)
         {
             fileInfo.CheckNotNull("fileInfo");
-            return new SevenZipArchive(fileInfo, readerOptions ?? new ReaderOptions());
+            return new SevenZipArchive(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 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>
@@ -44,17 +69,23 @@ namespace SharpCompress.Archives.SevenZip
         public static SevenZipArchive Open(Stream stream, ReaderOptions readerOptions = null)
         {
             stream.CheckNotNull("stream");
-            return new SevenZipArchive(stream, readerOptions ?? new ReaderOptions());
+            return new SevenZipArchive(new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions()));
         }
 
-        internal SevenZipArchive(FileInfo fileInfo, ReaderOptions readerOptions)
-            : base(ArchiveType.SevenZip, fileInfo, 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)
         {
         }
 
-        protected override IEnumerable<SevenZipVolume> LoadVolumes(FileInfo file)
+        protected override IEnumerable<SevenZipVolume> LoadVolumes(SourceStream srcStream)
         {
-            return new SevenZipVolume(file.OpenRead(), ReaderOptions).AsEnumerable();
+            base.SrcStream.LoadAllParts(); //request all streams
+            return new SevenZipVolume(srcStream, ReaderOptions).AsEnumerable(); //simple single volume or split, multivolume not supported
         }
 
         public static bool IsSevenZipFile(string filePath)
@@ -74,38 +105,32 @@ 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];
-                yield return new SevenZipArchiveEntry(this, new SevenZipFilePart(stream, database, i, file, ReaderOptions.ArchiveEncoding));
+                entries[i] = 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)
@@ -131,7 +156,7 @@ namespace SharpCompress.Archives.SevenZip
             }
         }
 
-        private static ReadOnlySpan<byte> SIGNATURE => new byte[] {(byte)'7', (byte)'z', 0xBC, 0xAF, 0x27, 0x1C};
+        private static ReadOnlySpan<byte> SIGNATURE => new byte[] { (byte)'7', (byte)'z', 0xBC, 0xAF, 0x27, 0x1C };
 
         private static bool SignatureMatch(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;
@@ -34,7 +34,31 @@ namespace SharpCompress.Archives.Tar
         public static TarArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            return new TarArchive(fileInfo, readerOptions ?? new ReaderOptions());
+            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()));
         }
 
         /// <summary>
@@ -45,7 +69,7 @@ namespace SharpCompress.Archives.Tar
         public static TarArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
-            return new TarArchive(stream, readerOptions ?? new ReaderOptions());
+            return new TarArchive(new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions()));
         }
 
         public static bool IsTarFile(string filePath)
@@ -79,29 +103,20 @@ namespace SharpCompress.Archives.Tar
             }
             return false;
         }
-        
-        /// <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)
-        {
-        }
 
-        protected override IEnumerable<TarVolume> LoadVolumes(FileInfo file)
+        protected override IEnumerable<TarVolume> LoadVolumes(SourceStream srcStream)
         {
-            return new TarVolume(file.OpenRead(), ReaderOptions).AsEnumerable();
+            base.SrcStream.LoadAllParts(); //request all streams
+            return new TarVolume(srcStream, ReaderOptions).AsEnumerable(); //simple single volume or split, multivolume not supported
         }
 
         /// <summary>
-        /// Takes multiple seekable Streams for a multi-part archive
+        /// Constructor with a SourceStream able to handle FileInfo and Streams.
         /// </summary>
-        /// <param name="stream"></param>
-        /// <param name="readerOptions"></param>
-        internal TarArchive(Stream stream, ReaderOptions readerOptions)
-            : base(ArchiveType.Tar, stream, readerOptions)
+        /// <param name="srcStream"></param>
+        /// <param name="options"></param>
+        internal TarArchive(SourceStream srcStream)
+            : base(ArchiveType.Tar, srcStream)
         {
         }
 
@@ -110,11 +125,6 @@ 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;
@@ -6,6 +6,7 @@ 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;
@@ -24,7 +25,18 @@ namespace SharpCompress.Archives.Zip
         /// if the compression method is set to deflate
         /// </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>
@@ -44,7 +56,31 @@ namespace SharpCompress.Archives.Zip
         public static ZipArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
-            return new ZipArchive(fileInfo, readerOptions ?? new ReaderOptions());
+            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()));
         }
 
         /// <summary>
@@ -55,9 +91,9 @@ namespace SharpCompress.Archives.Zip
         public static ZipArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
-            return new ZipArchive(stream, readerOptions ?? new ReaderOptions());
+            return new ZipArchive(new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions()));
         }
-        
+
         public static bool IsZipFile(string filePath, string? password = null)
         {
             return IsZipFile(new FileInfo(filePath), password);
@@ -80,8 +116,7 @@ namespace SharpCompress.Archives.Zip
             StreamingZipHeaderFactory headerFactory = new StreamingZipHeaderFactory(password, new ArchiveEncoding());
             try
             {
-                ZipHeader header =
-                    headerFactory.ReadStreamHeader(stream).FirstOrDefault(x => x.ZipHeaderType != ZipHeaderType.Split);
+                ZipHeader? header = headerFactory.ReadStreamHeader(stream).FirstOrDefault(x => x.ZipHeaderType != ZipHeaderType.Split);
                 if (header is null)
                 {
                     return false;
@@ -97,21 +132,62 @@ namespace SharpCompress.Archives.Zip
                 return false;
             }
         }
-        
-        /// <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)
+
+        public static bool IsZipMulti(Stream stream, string? password = null)
         {
-            headerFactory = new SeekableZipHeaderFactory(readerOptions.Password, readerOptions.ArchiveEncoding);
+            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;
+            }
         }
 
-        protected override IEnumerable<ZipVolume> LoadVolumes(FileInfo file)
+        protected override IEnumerable<ZipVolume> LoadVolumes(SourceStream srcStream)
         {
-            return new ZipVolume(file.OpenRead(), ReaderOptions).AsEnumerable();
+            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();
         }
 
         internal ZipArchive()
@@ -119,46 +195,35 @@ 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 volume = volumes.Single();
-            Stream stream = volume.Stream;
-            foreach (ZipHeader h in headerFactory.ReadSeekableHeader(stream))
+            var vols = volumes.ToArray();
+            foreach (ZipHeader h in headerFactory.ReadSeekableHeader(vols.Last().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)
                             {
-                                yield return new ZipArchiveEntry(this,
-                                                                 new SeekableZipFilePart(headerFactory,
-                                                                                         (DirectoryEntryHeader)h,
-                                                                                         stream));
+                                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 });
                             }
-                            break;
+                            else
+                                s = vols[deh.DiskNumberStart].Stream;
+                            yield return new ZipArchiveEntry(this, new SeekableZipFilePart(headerFactory, deh, s));
+                        }
+                        break;
                         case ZipHeaderType.DirectoryEnd:
-                            {
-                                byte[] bytes = ((DirectoryEndHeader)h).Comment ?? Array.Empty<byte>();
-                                volume.Comment = ReaderOptions.ArchiveEncoding.Decode(bytes);
-                                yield break;
-                            }
+                        {
+                            byte[] bytes = ((DirectoryEndHeader)h).Comment ?? Array.Empty<byte>();
+                            volumes.Last().Comment = ReaderOptions.ArchiveEncoding.Decode(bytes);
+                            yield break;
+                        }
                     }
                 }
             }

src/SharpCompress/Archives/Zip/ZipArchiveVolumeFactory.cs

@@ -0,0 +1,34 @@
+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/Common/ArchiveEncoding.cs

@@ -36,7 +36,7 @@ namespace SharpCompress.Common
             Password = password;
         }
 
-#if NETSTANDARD1_3 || NETSTANDARD2_0 || NETSTANDARD2_1
+#if !NETFRAMEWORK
         static ArchiveEncoding()
         {
             Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);

src/SharpCompress/Common/Entry.cs

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

src/SharpCompress/Common/EntryStream.cs

@@ -47,7 +47,8 @@ namespace SharpCompress.Common
 
         public override bool CanWrite => false;
 
-        public override void Flush() {
+        public override void Flush()
+        {
         }
 
         public override long Length => _stream.Length;

src/SharpCompress/Common/ExtractionMethods.cs

@@ -8,30 +8,39 @@ namespace SharpCompress.Common
         /// <summary>
         /// Extract to specific directory, retaining filename
         /// </summary>
-        public static void WriteEntryToDirectory(IEntry entry, 
+        public static void WriteEntryToDirectory(IEntry entry,
                                                  string destinationDirectory,
-                                                 ExtractionOptions? options, 
+                                                 ExtractionOptions? options,
                                                  Action<string, ExtractionOptions?> write)
         {
             string destinationFileName;
-            string file = Path.GetFileName(entry.Key);
             string fullDestinationDirectoryPath = Path.GetFullPath(destinationDirectory);
 
-            options ??= new ExtractionOptions()
-                        {
-                            Overwrite = true
-                        };
+            //check for trailing slash.
+            if (fullDestinationDirectoryPath[fullDestinationDirectoryPath.Length - 1] != Path.DirectorySeparatorChar)
+            {
+                fullDestinationDirectoryPath += Path.DirectorySeparatorChar;
+            }
 
+            if (!Directory.Exists(fullDestinationDirectoryPath))
+            {
+                throw new ExtractionException($"Directory does not exist to extract to: {fullDestinationDirectoryPath}");
+            }
+
+            options ??= new ExtractionOptions()
+            {
+                Overwrite = true
+            };
+
+            string file = Path.GetFileName(entry.Key);
             if (options.ExtractFullPath)
             {
-                string folder = Path.GetDirectoryName(entry.Key);
-                string destdir = Path.GetFullPath(
-                                                  Path.Combine(fullDestinationDirectoryPath, folder)
-                                                 );
+                string folder = Path.GetDirectoryName(entry.Key)!;
+                string destdir = Path.GetFullPath(Path.Combine(fullDestinationDirectoryPath, folder));
 
                 if (!Directory.Exists(destdir))
                 {
-                    if (!destdir.StartsWith(fullDestinationDirectoryPath))
+                    if (!destdir.StartsWith(fullDestinationDirectoryPath, StringComparison.Ordinal))
                     {
                         throw new ExtractionException("Entry is trying to create a directory outside of the destination directory.");
                     }
@@ -41,7 +50,7 @@ namespace SharpCompress.Common
                 destinationFileName = Path.Combine(destdir, file);
             }
             else
-            {        
+            {
                 destinationFileName = Path.Combine(fullDestinationDirectoryPath, file);
 
             }
@@ -50,7 +59,7 @@ namespace SharpCompress.Common
             {
                 destinationFileName = Path.GetFullPath(destinationFileName);
 
-                if (!destinationFileName.StartsWith(fullDestinationDirectoryPath))
+                if (!destinationFileName.StartsWith(fullDestinationDirectoryPath, StringComparison.Ordinal))
                 {
                     throw new ExtractionException("Entry is trying to write a file outside of the destination directory.");
                 }
@@ -61,7 +70,7 @@ namespace SharpCompress.Common
                 Directory.CreateDirectory(destinationFileName);
             }
         }
-        
+
         public static void WriteEntryToFile(IEntry entry, string destinationFileName,
                                             ExtractionOptions? options,
                                             Action<string, FileMode> openAndWrite)
@@ -78,9 +87,9 @@ namespace SharpCompress.Common
             {
                 FileMode fm = FileMode.Create;
                 options ??= new ExtractionOptions()
-                                {
-                                    Overwrite = true
-                                };
+                {
+                    Overwrite = true
+                };
 
                 if (!options.Overwrite)
                 {

src/SharpCompress/Common/ExtractionOptions.cs

@@ -7,7 +7,7 @@ namespace SharpCompress.Common
         /// <summary>
         /// overwrite target if it exists
         /// </summary>
-        public bool Overwrite  {get; set; }
+        public bool Overwrite { get; set; }
 
         /// <summary>
         /// extract with internal directory structure

src/SharpCompress/Common/GZip/GZipEntry.cs

@@ -15,7 +15,7 @@ namespace SharpCompress.Common.GZip
 
         public override CompressionType CompressionType => CompressionType.GZip;
 
-        public override long Crc => 0;
+        public override long Crc => _filePart.Crc ?? 0;
 
         public override string Key => _filePart.FilePartName;
 
@@ -23,7 +23,7 @@ namespace SharpCompress.Common.GZip
 
         public override long CompressedSize => 0;
 
-        public override long Size => 0;
+        public override long Size => _filePart.UncompressedSize ?? 0;
 
         public override DateTime? LastModifiedTime => _filePart.DateModified;
 

src/SharpCompress/Common/GZip/GZipFilePart.cs

@@ -8,7 +8,7 @@ using SharpCompress.Compressors.Deflate;
 
 namespace SharpCompress.Common.GZip
 {
-    internal class GZipFilePart : FilePart
+    internal sealed class GZipFilePart : FilePart
     {
         private string? _name;
         private readonly Stream _stream;
@@ -16,14 +16,23 @@ namespace SharpCompress.Common.GZip
         internal GZipFilePart(Stream stream, ArchiveEncoding archiveEncoding)
             : base(archiveEncoding)
         {
-            ReadAndValidateGzipHeader(stream);
-            EntryStartPosition = stream.Position;
             _stream = stream;
+            ReadAndValidateGzipHeader();
+            if (stream.CanSeek)
+            {
+                long position = stream.Position;
+                stream.Position = stream.Length - 8;
+                ReadTrailer();
+                stream.Position = position;
+            }
+            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!;
 
@@ -37,11 +46,21 @@ namespace SharpCompress.Common.GZip
             return _stream;
         }
 
-        private void ReadAndValidateGzipHeader(Stream stream)
+        private void ReadTrailer()
+        {
+            // Read and potentially verify the GZIP trailer: CRC32 and  size mod 2^32
+            Span<byte> trailer = stackalloc byte[8];
+            int n = _stream.Read(trailer);
+
+            Crc = BinaryPrimitives.ReadInt32LittleEndian(trailer);
+            UncompressedSize = BinaryPrimitives.ReadInt32LittleEndian(trailer.Slice(4));
+        }
+
+        private void ReadAndValidateGzipHeader()
         {
             // read the header on the first read
-            byte[] header = new byte[10];
-            int n = stream.Read(header, 0, header.Length);
+            Span<byte> header = stackalloc byte[10];
+            int n = _stream.Read(header);
 
             // workitem 8501: handle edge case (decompress empty stream)
             if (n == 0)
@@ -59,17 +78,17 @@ namespace SharpCompress.Common.GZip
                 throw new ZlibException("Bad GZIP header.");
             }
 
-            int timet = BinaryPrimitives.ReadInt32LittleEndian(header.AsSpan(4));
+            int timet = BinaryPrimitives.ReadInt32LittleEndian(header.Slice(4));
             DateModified = TarHeader.EPOCH.AddSeconds(timet);
             if ((header[3] & 0x04) == 0x04)
             {
                 // read and discard extra field
-                n = stream.Read(header, 0, 2); // 2-byte length field
+                n = _stream.Read(header.Slice(0, 2)); // 2-byte length field
 
-                Int16 extraLength = (Int16)(header[0] + header[1] * 256);
+                short extraLength = (short)(header[0] + header[1] * 256);
                 byte[] extra = new byte[extraLength];
 
-                if (!stream.ReadFully(extra))
+                if (!_stream.ReadFully(extra))
                 {
                     throw new ZlibException("Unexpected end-of-file reading GZIP header.");
                 }
@@ -77,27 +96,27 @@ namespace SharpCompress.Common.GZip
             }
             if ((header[3] & 0x08) == 0x08)
             {
-                _name = ReadZeroTerminatedString(stream);
+                _name = ReadZeroTerminatedString(_stream);
             }
             if ((header[3] & 0x10) == 0x010)
             {
-                ReadZeroTerminatedString(stream);
+                ReadZeroTerminatedString(_stream);
             }
             if ((header[3] & 0x02) == 0x02)
             {
-                stream.ReadByte(); // CRC16, ignore
+                _stream.ReadByte(); // CRC16, ignore
             }
         }
 
         private string ReadZeroTerminatedString(Stream stream)
         {
-            byte[] buf1 = new byte[1];
+            Span<byte> buf1 = stackalloc byte[1];
             var list = new List<byte>();
             bool done = false;
             do
             {
                 // workitem 7740
-                int n = stream.Read(buf1, 0, 1);
+                int n = stream.Read(buf1);
                 if (n != 1)
                 {
                     throw new ZlibException("Unexpected EOF reading GZIP header.");

src/SharpCompress/Common/IEntry.cs

@@ -14,6 +14,7 @@ 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/Headers/AVHeader.cs

@@ -4,8 +4,8 @@ namespace SharpCompress.Common.Rar.Headers
 {
     internal class AvHeader : RarHeader
     {
-        public AvHeader(RarHeader header, RarCrcBinaryReader reader) 
-            : base(header, reader, HeaderType.Av) 
+        public AvHeader(RarHeader header, RarCrcBinaryReader reader)
+            : base(header, reader, HeaderType.Av)
         {
             if (IsRar5)
             {

src/SharpCompress/Common/Rar/Headers/ArchiveCryptHeader.cs

@@ -6,7 +6,7 @@ namespace SharpCompress.Common.Rar.Headers
 {
     internal class ArchiveCryptHeader : RarHeader
     {
-        
+
         private const int CRYPT_VERSION = 0; // Supported encryption version.
         private const int SIZE_SALT50 = 16;
         private const int SIZE_SALT30 = 8;
@@ -15,14 +15,14 @@ namespace SharpCompress.Common.Rar.Headers
         private const int SIZE_PSWCHECK_CSUM = 4;
         private const int CRYPT5_KDF_LG2_COUNT = 15; // LOG2 of PDKDF2 iteration count.
         private const int CRYPT5_KDF_LG2_COUNT_MAX = 24; // LOG2 of maximum accepted iteration count.
-        
-        
+
+
         private bool _usePswCheck;
         private uint _lg2Count; // Log2 of PBKDF2 repetition count.
         private byte[] _salt;
         private byte[] _pswCheck;
         private byte[] _pswCheckCsm;
-        
+
         public ArchiveCryptHeader(RarHeader header, RarCrcBinaryReader reader)
             : base(header, reader, HeaderType.Crypt)
         {
@@ -35,12 +35,12 @@ namespace SharpCompress.Common.Rar.Headers
             {
                 //error?
                 return;
-            } 
+            }
             var encryptionFlags = reader.ReadRarVIntUInt32();
             _usePswCheck = FlagUtility.HasFlag(encryptionFlags, EncryptionFlagsV5.CHFL_CRYPT_PSWCHECK);
             _lg2Count = reader.ReadRarVIntByte(1);
 
-            
+
             //UsePswCheck = HasHeaderFlag(EncryptionFlagsV5.CHFL_CRYPT_PSWCHECK);
             if (_lg2Count > CRYPT5_KDF_LG2_COUNT_MAX)
             {

src/SharpCompress/Common/Rar/Headers/ArchiveHeader.cs

@@ -4,14 +4,14 @@ namespace SharpCompress.Common.Rar.Headers
 {
     internal sealed class ArchiveHeader : RarHeader
     {
-        public ArchiveHeader(RarHeader header, RarCrcBinaryReader reader) 
-            : base(header, reader, HeaderType.Archive) 
+        public ArchiveHeader(RarHeader header, RarCrcBinaryReader reader)
+            : base(header, reader, HeaderType.Archive)
         {
         }
 
         protected override void ReadFinish(MarkingBinaryReader reader)
         {
-            if (IsRar5) 
+            if (IsRar5)
             {
                 Flags = reader.ReadRarVIntUInt16();
                 if (HasFlag(ArchiveFlagsV5.HAS_VOLUME_NUMBER))
@@ -22,8 +22,8 @@ namespace SharpCompress.Common.Rar.Headers
                 //if (ExtraSize != 0) {
                 //    ReadLocator(reader);
                 //}
-            } 
-            else 
+            }
+            else
             {
                 Flags = HeaderFlags;
                 HighPosAv = reader.ReadInt16();
@@ -35,7 +35,8 @@ namespace SharpCompress.Common.Rar.Headers
             }
         }
 
-        private void ReadLocator(MarkingBinaryReader reader) {
+        private void ReadLocator(MarkingBinaryReader reader)
+        {
             var size = reader.ReadRarVIntUInt16();
             var type = reader.ReadRarVIntUInt16();
             if (type != 1)
@@ -47,18 +48,20 @@ namespace SharpCompress.Common.Rar.Headers
             const ushort hasQuickOpenOffset = 0x01;
             const ushort hasRecoveryOffset = 0x02;
             ulong quickOpenOffset = 0;
-            if ((flags & hasQuickOpenOffset) == hasQuickOpenOffset) { 
+            if ((flags & hasQuickOpenOffset) == hasQuickOpenOffset)
+            {
                 quickOpenOffset = reader.ReadRarVInt();
             }
             ulong recoveryOffset = 0;
-            if ((flags & hasRecoveryOffset) == hasRecoveryOffset) { 
+            if ((flags & hasRecoveryOffset) == hasRecoveryOffset)
+            {
                 recoveryOffset = reader.ReadRarVInt();
             }
         }
 
-        private ushort Flags  { get; set; }
+        private ushort Flags { get; set; }
 
-        private bool HasFlag(ushort flag) 
+        private bool HasFlag(ushort flag)
         {
             return (Flags & flag) == flag;
         }

src/SharpCompress/Common/Rar/Headers/CommentHeader.cs

@@ -5,8 +5,8 @@ namespace SharpCompress.Common.Rar.Headers
     internal class CommentHeader : RarHeader
     {
         protected CommentHeader(RarHeader header, RarCrcBinaryReader reader)
-            : base(header, reader, HeaderType.Comment) 
-        { 
+            : base(header, reader, HeaderType.Comment)
+        {
             if (IsRar5)
             {
                 throw new InvalidFormatException("unexpected rar5 record");

src/SharpCompress/Common/Rar/Headers/EndArchiveHeader.cs

@@ -4,14 +4,14 @@ namespace SharpCompress.Common.Rar.Headers
 {
     internal class EndArchiveHeader : RarHeader
     {
-        public EndArchiveHeader(RarHeader header, RarCrcBinaryReader reader) 
-            : base(header, reader, HeaderType.EndArchive) 
+        public EndArchiveHeader(RarHeader header, RarCrcBinaryReader reader)
+            : base(header, reader, HeaderType.EndArchive)
         {
         }
 
         protected override void ReadFinish(MarkingBinaryReader reader)
         {
-            if (IsRar5) 
+            if (IsRar5)
             {
                 Flags = reader.ReadRarVIntUInt16();
             }
@@ -31,7 +31,7 @@ namespace SharpCompress.Common.Rar.Headers
 
         private ushort Flags { get; set; }
 
-        private bool HasFlag(ushort flag) 
+        private bool HasFlag(ushort flag)
         {
             return (Flags & flag) == flag;
         }

src/SharpCompress/Common/Rar/Headers/FileHeader.cs

@@ -21,18 +21,18 @@ namespace SharpCompress.Common.Rar.Headers
     {
         private uint _fileCrc;
 
-        public FileHeader(RarHeader header, RarCrcBinaryReader reader, HeaderType headerType) 
-            : base(header, reader, headerType) 
+        public FileHeader(RarHeader header, RarCrcBinaryReader reader, HeaderType headerType)
+            : base(header, reader, headerType)
         {
         }
 
-        protected override void ReadFinish(MarkingBinaryReader reader) 
+        protected override void ReadFinish(MarkingBinaryReader reader)
         {
-            if (IsRar5) 
+            if (IsRar5)
             {
                 ReadFromReaderV5(reader);
-            } 
-            else 
+            }
+            else
             {
                 ReadFromReaderV4(reader);
             }
@@ -49,11 +49,13 @@ namespace SharpCompress.Common.Rar.Headers
 
             FileAttributes = reader.ReadRarVIntUInt32();
 
-            if (HasFlag(FileFlagsV5.HAS_MOD_TIME)) {
+            if (HasFlag(FileFlagsV5.HAS_MOD_TIME))
+            {
                 FileLastModifiedTime = Utility.UnixTimeToDateTime(reader.ReadUInt32());
             }
 
-            if (HasFlag(FileFlagsV5.HAS_CRC32)) {
+            if (HasFlag(FileFlagsV5.HAS_CRC32))
+            {
                 FileCrc = reader.ReadUInt32();
             }
 
@@ -65,7 +67,7 @@ namespace SharpCompress.Common.Rar.Headers
             // but it was already used in RAR 1.5 and Unpack needs to distinguish
             // them.
             CompressionAlgorithm = (byte)((compressionInfo & 0x3f) + 50);
-            
+
             // 7th bit (0x0040) defines the solid flag. If it is set, RAR continues to use the compression dictionary left after processing preceding files. 
             // It can be set only for file headers and is never set for service headers.
             IsSolid = (compressionInfo & 0x40) == 0x40;
@@ -74,7 +76,7 @@ namespace SharpCompress.Common.Rar.Headers
             CompressionMethod = (byte)((compressionInfo >> 7) & 0x7);
 
             // Bits 11 - 14 (0x3c00) define the minimum size of dictionary size required to extract data. Value 0 means 128 KB, 1 - 256 KB, ..., 14 - 2048 MB, 15 - 4096 MB.
-            WindowSize = IsDirectory ? 0 : ((size_t)0x20000) << ((compressionInfo>>10) & 0xf);
+            WindowSize = IsDirectory ? 0 : ((size_t)0x20000) << ((compressionInfo >> 10) & 0xf);
 
             HostOs = reader.ReadRarVIntByte();
 
@@ -101,18 +103,20 @@ namespace SharpCompress.Common.Rar.Headers
             FileName = ConvertPathV5(Encoding.UTF8.GetString(b, 0, b.Length));
 
             // extra size seems to be redudant since we know the total header size
-            if (ExtraSize != RemainingHeaderBytes(reader)) 
+            if (ExtraSize != RemainingHeaderBytes(reader))
             {
                 throw new InvalidFormatException("rar5 header size / extra size inconsistency");
             }
 
             isEncryptedRar5 = false;
 
-            while (RemainingHeaderBytes(reader) > 0) {
+            while (RemainingHeaderBytes(reader) > 0)
+            {
                 var size = reader.ReadRarVIntUInt16();
                 int n = RemainingHeaderBytes(reader);
                 var type = reader.ReadRarVIntUInt16();
-                switch (type) {
+                switch (type)
+                {
                     //TODO
                     case 1: // file encryption
                         {
@@ -120,7 +124,7 @@ namespace SharpCompress.Common.Rar.Headers
 
                             //var version = reader.ReadRarVIntByte();
                             //if (version != 0) throw new InvalidFormatException("unknown encryption algorithm " + version);
-                                                    }
+                        }
                         break;
                     //                    case 2: // file hash
                     //                        {
@@ -131,38 +135,41 @@ namespace SharpCompress.Common.Rar.Headers
                         {
                             ushort flags = reader.ReadRarVIntUInt16();
                             var isWindowsTime = (flags & 1) == 0;
-                            if ((flags & 0x2) == 0x2) {
+                            if ((flags & 0x2) == 0x2)
+                            {
                                 FileLastModifiedTime = ReadExtendedTimeV5(reader, isWindowsTime);
                             }
-                            if ((flags & 0x4) == 0x4) {
+                            if ((flags & 0x4) == 0x4)
+                            {
                                 FileCreatedTime = ReadExtendedTimeV5(reader, isWindowsTime);
                             }
-                            if ((flags & 0x8) == 0x8) {
+                            if ((flags & 0x8) == 0x8)
+                            {
                                 FileLastAccessedTime = ReadExtendedTimeV5(reader, isWindowsTime);
                             }
                         }
                         break;
-//TODO
-//                    case 4: // file version
-//                        {
-//
-//                        }
-//                        break;
-//                    case 5: // file system redirection
-//                        {
-//
-//                        }
-//                        break;
-//                    case 6: // unix owner
-//                        {
-//
-//                        }
-//                        break;
-//                    case 7: // service data
-//                        {
-//
-//                        }
-//                        break;
+                    //TODO
+                    //                    case 4: // file version
+                    //                        {
+                    //
+                    //                        }
+                    //                        break;
+                    //                    case 5: // file system redirection
+                    //                        {
+                    //
+                    //                        }
+                    //                        break;
+                    //                    case 6: // unix owner
+                    //                        {
+                    //
+                    //                        }
+                    //                        break;
+                    //                    case 7: // service data
+                    //                        {
+                    //
+                    //                        }
+                    //                        break;
 
                     default:
                         // skip unknown record types to allow new record types to be added in the future
@@ -171,25 +178,26 @@ namespace SharpCompress.Common.Rar.Headers
                 // drain any trailing bytes of extra record
                 int did = n - RemainingHeaderBytes(reader);
                 int drain = size - did;
-                if (drain > 0) 
+                if (drain > 0)
                 {
                     reader.ReadBytes(drain);
                 }
             }
 
-            if (AdditionalDataSize != 0) {
+            if (AdditionalDataSize != 0)
+            {
                 CompressedSize = AdditionalDataSize;
             }
         }
 
 
-        private static DateTime ReadExtendedTimeV5(MarkingBinaryReader reader, bool isWindowsTime) 
+        private static DateTime ReadExtendedTimeV5(MarkingBinaryReader reader, bool isWindowsTime)
         {
-            if (isWindowsTime) 
+            if (isWindowsTime)
             {
                 return DateTime.FromFileTime(reader.ReadInt64());
-            } 
-            else 
+            }
+            else
             {
                 return Utility.UnixTimeToDateTime(reader.ReadUInt32());
             }
@@ -201,7 +209,7 @@ namespace SharpCompress.Common.Rar.Headers
             {
                 // replace embedded \\ with valid filename char
                 return path.Replace('\\', '-').Replace('/', '\\');
-            } 
+            }
             return path;
         }
 
@@ -376,20 +384,22 @@ namespace SharpCompress.Common.Rar.Headers
 
         private ushort Flags { get; set; }
 
-        private bool HasFlag(ushort flag) 
+        private bool HasFlag(ushort flag)
         {
             return (Flags & flag) == flag;
         }
 
-        internal uint FileCrc 
-        { 
-            get { 
-                if (IsRar5 && !HasFlag(FileFlagsV5.HAS_CRC32)) {
-//!!! rar5: 
+        internal uint FileCrc
+        {
+            get
+            {
+                if (IsRar5 && !HasFlag(FileFlagsV5.HAS_CRC32))
+                {
+                    //!!! rar5: 
                     throw new InvalidOperationException("TODO rar5");
                 }
-                return _fileCrc; 
-            } 
+                return _fileCrc;
+            }
             private set => _fileCrc = value;
         }
 
@@ -409,7 +419,7 @@ namespace SharpCompress.Common.Rar.Headers
         //case 29: // rar 3.x compression
         //case 50: // RAR 5.0 compression algorithm.
         internal byte CompressionAlgorithm { get; private set; }
-        
+
         public bool IsSolid { get; private set; }
 
         // unused for UnpackV1 implementation (limitation)
@@ -427,13 +437,14 @@ namespace SharpCompress.Common.Rar.Headers
         internal long DataStartPosition { get; set; }
         public Stream PackedStream { get; set; }
 
+        public bool IsSplitBefore => IsRar5 ? HasHeaderFlag(HeaderFlagsV5.SPLIT_BEFORE) : HasFlag(FileFlagsV4.SPLIT_BEFORE);
         public bool IsSplitAfter => IsRar5 ? HasHeaderFlag(HeaderFlagsV5.SPLIT_AFTER) : HasFlag(FileFlagsV4.SPLIT_AFTER);
 
         public bool IsDirectory => HasFlag(IsRar5 ? FileFlagsV5.DIRECTORY : FileFlagsV4.DIRECTORY);
 
         private bool isEncryptedRar5 = false;
-        public bool IsEncrypted => IsRar5 ? isEncryptedRar5: HasFlag(FileFlagsV4.PASSWORD);
-        
+        public bool IsEncrypted => IsRar5 ? isEncryptedRar5 : HasFlag(FileFlagsV4.PASSWORD);
+
         internal DateTime? FileLastModifiedTime { get; private set; }
 
         internal DateTime? FileCreatedTime { get; private set; }

src/SharpCompress/Common/Rar/Headers/Flags.cs

@@ -42,10 +42,10 @@ namespace SharpCompress.Common.Rar.Headers
     }
 
     internal static class EncryptionFlagsV5
-    {   
+    {
         // RAR 5.0 archive encryption header specific flags.
         public const uint CHFL_CRYPT_PSWCHECK = 0x01; // Password check data is present.
-        
+
         public const uint FHEXTRA_CRYPT_PSWCHECK = 0x01; // Password check data is present.
         public const uint FHEXTRA_CRYPT_HASHMAC = 0x02;
     }

src/SharpCompress/Common/Rar/Headers/IRarHeader.cs

@@ -1,6 +1,6 @@
 namespace SharpCompress.Common.Rar.Headers
 {
-    internal interface IRarHeader 
+    internal interface IRarHeader
     {
         HeaderType HeaderType { get; }
     }

src/SharpCompress/Common/Rar/Headers/MarkHeader.cs

@@ -11,39 +11,39 @@ namespace SharpCompress.Common.Rar.Headers
 
         public bool IsRar5 { get; }
 
-        private MarkHeader(bool isRar5) 
-        { 
+        private MarkHeader(bool isRar5)
+        {
             IsRar5 = isRar5;
         }
 
         public HeaderType HeaderType => HeaderType.Mark;
 
-        private static byte GetByte(Stream stream) 
+        private static byte GetByte(Stream stream)
         {
             var b = stream.ReadByte();
-            if (b != -1) 
+            if (b != -1)
             {
                 return (byte)b;
             }
             throw new EndOfStreamException();
         }
 
-        public static MarkHeader Read(Stream stream, bool leaveStreamOpen, bool lookForHeader) 
+        public static MarkHeader Read(Stream stream, bool leaveStreamOpen, bool lookForHeader)
         {
             int maxScanIndex = lookForHeader ? MAX_SFX_SIZE : 0;
             try
             {
                 int start = -1;
                 var b = GetByte(stream); start++;
-                while (start <= maxScanIndex) 
+                while (start <= maxScanIndex)
                 {
                     // Rar old signature: 52 45 7E 5E
                     // Rar4 signature:    52 61 72 21 1A 07 00
                     // Rar5 signature:    52 61 72 21 1A 07 01 00
-                    if (b == 0x52) 
+                    if (b == 0x52)
                     {
                         b = GetByte(stream); start++;
-                        if (b == 0x61) 
+                        if (b == 0x61)
                         {
                             b = GetByte(stream); start++;
                             if (b != 0x72)
@@ -70,7 +70,7 @@ namespace SharpCompress.Common.Rar.Headers
                             }
 
                             b = GetByte(stream); start++;
-                            if (b == 1) 
+                            if (b == 1)
                             {
                                 b = GetByte(stream); start++;
                                 if (b != 0)
@@ -79,13 +79,13 @@ namespace SharpCompress.Common.Rar.Headers
                                 }
 
                                 return new MarkHeader(true); // Rar5
-                            } 
-                            else if (b == 0) 
+                            }
+                            else if (b == 0)
                             {
                                 return new MarkHeader(false); // Rar4
-                            } 
-                        } 
-                        else if (b == 0x45) 
+                            }
+                        }
+                        else if (b == 0x45)
                         {
                             b = GetByte(stream); start++;
                             if (b != 0x7e)
@@ -100,9 +100,9 @@ namespace SharpCompress.Common.Rar.Headers
                             }
 
                             throw new InvalidFormatException("Rar format version pre-4 is unsupported.");
-                        } 
-                    } 
-                    else 
+                        }
+                    }
+                    else
                     {
                         b = GetByte(stream); start++;
                     }

src/SharpCompress/Common/Rar/Headers/NewSubHeaderType.cs

@@ -2,23 +2,23 @@
 
 namespace SharpCompress.Common.Rar.Headers
 {
-    internal class NewSubHeaderType : IEquatable<NewSubHeaderType>
+    internal sealed class NewSubHeaderType : IEquatable<NewSubHeaderType>
     {
-        internal static readonly NewSubHeaderType SUBHEAD_TYPE_CMT = new NewSubHeaderType('C', 'M', 'T');
+        internal static readonly NewSubHeaderType SUBHEAD_TYPE_CMT = new('C', 'M', 'T');
 
-        //internal static final NewSubHeaderType SUBHEAD_TYPE_ACL = new NewSubHeaderType(new byte[]{'A','C','L'});
+        //internal static final NewSubHeaderType SUBHEAD_TYPE_ACL = new (new byte[]{'A','C','L'});
 
-        //internal static final NewSubHeaderType SUBHEAD_TYPE_STREAM = new NewSubHeaderType(new byte[]{'S','T','M'});
+        //internal static final NewSubHeaderType SUBHEAD_TYPE_STREAM = new (new byte[]{'S','T','M'});
 
-        //internal static final NewSubHeaderType SUBHEAD_TYPE_UOWNER = new NewSubHeaderType(new byte[]{'U','O','W'});
+        //internal static final NewSubHeaderType SUBHEAD_TYPE_UOWNER = new (new byte[]{'U','O','W'});
 
-        //internal static final NewSubHeaderType SUBHEAD_TYPE_AV = new NewSubHeaderType(new byte[]{'A','V'});
+        //internal static final NewSubHeaderType SUBHEAD_TYPE_AV = new (new byte[]{'A','V'});
 
-        internal static readonly NewSubHeaderType SUBHEAD_TYPE_RR = new NewSubHeaderType('R', 'R');
+        internal static readonly NewSubHeaderType SUBHEAD_TYPE_RR = new('R', 'R');
 
-        //internal static final NewSubHeaderType SUBHEAD_TYPE_OS2EA = new NewSubHeaderType(new byte[]{'E','A','2'});
+        //internal static final NewSubHeaderType SUBHEAD_TYPE_OS2EA = new (new byte[]{'E','A','2'});
 
-        //internal static final NewSubHeaderType SUBHEAD_TYPE_BEOSEA = new NewSubHeaderType(new byte[]{'E','A','B','E'});
+        //internal static final NewSubHeaderType SUBHEAD_TYPE_BEOSEA = new (new byte[]{'E','A','B','E'});
 
         private readonly byte[] _bytes;
 
@@ -37,19 +37,13 @@ namespace SharpCompress.Common.Rar.Headers
             {
                 return false;
             }
-            for (int i = 0; i < bytes.Length; ++i)
-            {
-                if (_bytes[i] != bytes[i])
-                {
-                    return false;
-                }
-            }
-            return true;
+
+            return _bytes.AsSpan().SequenceEqual(bytes);
         }
 
-        public bool Equals(NewSubHeaderType other)
+        public bool Equals(NewSubHeaderType? other)
         {
-            return Equals(other._bytes);
+            return other is not null && Equals(other._bytes);
         }
     }
 }

src/SharpCompress/Common/Rar/Headers/ProtectHeader.cs

@@ -5,8 +5,8 @@ namespace SharpCompress.Common.Rar.Headers
     // ProtectHeader is part of the Recovery Record feature
     internal sealed class ProtectHeader : RarHeader
     {
-        public ProtectHeader(RarHeader header, RarCrcBinaryReader reader) 
-            : base(header, reader, HeaderType.Protect) 
+        public ProtectHeader(RarHeader header, RarCrcBinaryReader reader)
+            : base(header, reader, HeaderType.Protect)
         {
             if (IsRar5)
             {

src/SharpCompress/Common/Rar/Headers/RarHeader.cs

@@ -23,12 +23,12 @@ namespace SharpCompress.Common.Rar.Headers
             }
         }
 
-        private RarHeader(RarCrcBinaryReader reader, bool isRar5, ArchiveEncoding archiveEncoding) 
+        private RarHeader(RarCrcBinaryReader reader, bool isRar5, ArchiveEncoding archiveEncoding)
         {
             _headerType = HeaderType.Null;
             _isRar5 = isRar5;
             ArchiveEncoding = archiveEncoding;
-            if (IsRar5) 
+            if (IsRar5)
             {
                 HeaderCrc = reader.ReadUInt32();
                 reader.ResetCrc();
@@ -45,7 +45,9 @@ namespace SharpCompress.Common.Rar.Headers
                 {
                     AdditionalDataSize = (long)reader.ReadRarVInt();
                 }
-            } else {
+            }
+            else
+            {
                 reader.Mark();
                 HeaderCrc = reader.ReadUInt16();
                 reader.ResetCrc();
@@ -59,7 +61,8 @@ namespace SharpCompress.Common.Rar.Headers
             }
         }
 
-        protected RarHeader(RarHeader header, RarCrcBinaryReader reader, HeaderType headerType) {
+        protected RarHeader(RarHeader header, RarCrcBinaryReader reader, HeaderType headerType)
+        {
             _headerType = headerType;
             _isRar5 = header.IsRar5;
             HeaderCrc = header.HeaderCrc;
@@ -80,7 +83,8 @@ namespace SharpCompress.Common.Rar.Headers
             VerifyHeaderCrc(reader.GetCrc32());
         }
 
-        protected int RemainingHeaderBytes(MarkingBinaryReader reader) {
+        protected int RemainingHeaderBytes(MarkingBinaryReader reader)
+        {
             return checked(HeaderSize - (int)reader.CurrentReadByteCount);
         }
 
@@ -108,7 +112,7 @@ namespace SharpCompress.Common.Rar.Headers
 
         protected ushort HeaderFlags { get; }
 
-        protected bool HasHeaderFlag(ushort flag) 
+        protected bool HasHeaderFlag(ushort flag)
         {
             return (HeaderFlags & flag) == flag;
         }

src/SharpCompress/Common/Rar/Headers/RarHeaderFactory.cs

@@ -41,11 +41,11 @@ namespace SharpCompress.Common.Rar.Headers
         private RarHeader? TryReadNextHeader(Stream stream)
         {
             RarCrcBinaryReader reader;
-            if (!IsEncrypted) 
+            if (!IsEncrypted)
             {
                 reader = new RarCrcBinaryReader(stream);
-            } 
-            else 
+            }
+            else
             {
                 if (Options.Password is null)
                 {
@@ -65,7 +65,7 @@ namespace SharpCompress.Common.Rar.Headers
                 case HeaderCodeV.RAR4_ARCHIVE_HEADER:
                     {
                         var ah = new ArchiveHeader(header, reader);
-                        if (ah.IsEncrypted == true) 
+                        if (ah.IsEncrypted == true)
                         {
                             //!!! rar5 we don't know yet
                             IsEncrypted = true;
@@ -150,11 +150,11 @@ namespace SharpCompress.Common.Rar.Headers
                         return new EndArchiveHeader(header, reader);
                     }
                 case HeaderCodeV.RAR5_ARCHIVE_ENCRYPTION_HEADER:
-                {
-                    var ch = new ArchiveCryptHeader(header, reader);
-                    IsEncrypted = true;
-                    return ch;
-                }
+                    {
+                        var ch = new ArchiveCryptHeader(header, reader);
+                        IsEncrypted = true;
+                        return ch;
+                    }
                 default:
                     {
                         throw new InvalidFormatException("Unknown Rar Header: " + header.HeaderCode);
@@ -162,21 +162,26 @@ namespace SharpCompress.Common.Rar.Headers
             }
         }
 
-        private void SkipData(FileHeader fh, RarCrcBinaryReader reader) {
-            switch (StreamingMode) {
-                case StreamingMode.Seekable: {
-                    fh.DataStartPosition = reader.BaseStream.Position;
-                    reader.BaseStream.Position += fh.CompressedSize;
-                }
+        private void SkipData(FileHeader fh, RarCrcBinaryReader reader)
+        {
+            switch (StreamingMode)
+            {
+                case StreamingMode.Seekable:
+                    {
+                        fh.DataStartPosition = reader.BaseStream.Position;
+                        reader.BaseStream.Position += fh.CompressedSize;
+                    }
                     break;
-                case StreamingMode.Streaming: {
-                    //skip the data because it's useless?
-                    reader.BaseStream.Skip(fh.CompressedSize);
-                }
+                case StreamingMode.Streaming:
+                    {
+                        //skip the data because it's useless?
+                        reader.BaseStream.Skip(fh.CompressedSize);
+                    }
                     break;
-                default: {
-                    throw new InvalidFormatException("Invalid StreamingMode");
-                }
+                default:
+                    {
+                        throw new InvalidFormatException("Invalid StreamingMode");
+                    }
             }
         }
     }

src/SharpCompress/Common/Rar/Headers/SignHeader.cs

@@ -5,8 +5,8 @@ namespace SharpCompress.Common.Rar.Headers
     internal class SignHeader : RarHeader
     {
         protected SignHeader(RarHeader header, RarCrcBinaryReader reader)
-            : base(header, reader, HeaderType.Sign) 
-        { 
+            : base(header, reader, HeaderType.Sign)
+        {
             if (IsRar5)
             {
                 throw new InvalidFormatException("unexpected rar5 record");

src/SharpCompress/Common/Rar/RarCryptoWrapper.cs

@@ -50,11 +50,11 @@ namespace SharpCompress.Common.Rar
             if (sizeToRead > 0)
             {
                 int alignedSize = sizeToRead + ((~sizeToRead + 1) & 0xf);
-                byte[] cipherText = new byte[RarRijndael.CRYPTO_BLOCK_SIZE];
+                Span<byte> cipherText = stackalloc byte[RarRijndael.CRYPTO_BLOCK_SIZE];
                 for (int i = 0; i < alignedSize / 16; i++)
                 {
                     //long ax = System.currentTimeMillis();
-                    _actualStream.Read(cipherText, 0, RarRijndael.CRYPTO_BLOCK_SIZE);
+                    _actualStream.Read(cipherText);
 
                     var readBytes = _rijndael.ProcessBlock(cipherText);
                     foreach (var readByte in readBytes)

src/SharpCompress/Common/Rar/RarEntry.cs

@@ -10,8 +10,8 @@ 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 == 29 || FileHeader.CompressionAlgorithm == 36;
-        
+        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
+
         /// <summary>
         /// The File's 32 bit CRC Hash
         /// </summary>

src/SharpCompress/Common/Rar/RarRijndael.cs

@@ -27,13 +27,13 @@ namespace SharpCompress.Common.Rar
 
             _rijndael = new RijndaelEngine();
             _aesInitializationVector = new byte[CRYPTO_BLOCK_SIZE];
-            int rawLength = 2*_password.Length;
+            int rawLength = 2 * _password.Length;
             byte[] rawPassword = new byte[rawLength + 8];
             byte[] passwordBytes = Encoding.UTF8.GetBytes(_password);
             for (int i = 0; i < _password.Length; i++)
             {
-                rawPassword[i*2] = passwordBytes[i];
-                rawPassword[i*2 + 1] = 0;
+                rawPassword[i * 2] = passwordBytes[i];
+                rawPassword[i * 2 + 1] = 0;
             }
             for (int i = 0; i < _salt.Length; i++)
             {
@@ -68,11 +68,11 @@ namespace SharpCompress.Common.Rar
             {
                 for (int j = 0; j < 4; j++)
                 {
-                    aesKey[i*4 + j] = (byte)
-                        (((digest[i*4]*0x1000000) & 0xff000000 |
-                          (uint) ((digest[i*4 + 1]*0x10000) & 0xff0000) |
-                          (uint) ((digest[i*4 + 2]*0x100) & 0xff00) |
-                          (uint) (digest[i*4 + 3] & 0xff)) >> (j*8));
+                    aesKey[i * 4 + j] = (byte)
+                        (((digest[i * 4] * 0x1000000) & 0xff000000 |
+                          (uint)((digest[i * 4 + 1] * 0x10000) & 0xff0000) |
+                          (uint)((digest[i * 4 + 2] * 0x100) & 0xff00) |
+                          (uint)(digest[i * 4 + 3] & 0xff)) >> (j * 8));
                 }
             }
 
@@ -87,11 +87,11 @@ namespace SharpCompress.Common.Rar
             return rijndael;
         }
 
-        public byte[] ProcessBlock(byte[] cipherText)
+        public byte[] ProcessBlock(ReadOnlySpan<byte> cipherText)
         {
-            var plainText = new byte[CRYPTO_BLOCK_SIZE];
+            Span<byte> plainText = stackalloc byte[CRYPTO_BLOCK_SIZE]; // 16 bytes
             byte[] decryptedBytes = new byte[CRYPTO_BLOCK_SIZE];
-            _rijndael.ProcessBlock(cipherText, 0, plainText, 0);
+            _rijndael.ProcessBlock(cipherText, plainText);
 
             for (int j = 0; j < CRYPTO_BLOCK_SIZE; j++)
             {

src/SharpCompress/Common/Rar/RarVolume.cs

@@ -39,20 +39,20 @@ namespace SharpCompress.Common.Rar
                 switch (header.HeaderType)
                 {
                     case HeaderType.Mark:
-                    {
-                        lastMarkHeader = (MarkHeader)header;
-                    }
+                        {
+                            lastMarkHeader = (MarkHeader)header;
+                        }
                         break;
                     case HeaderType.Archive:
-                    {
-                        ArchiveHeader = (ArchiveHeader)header;
-                    }
+                        {
+                            ArchiveHeader = (ArchiveHeader)header;
+                        }
                         break;
                     case HeaderType.File:
-                    {
-                        var fh = (FileHeader)header;
-                        yield return CreateFilePart(lastMarkHeader!, fh);
-                    }
+                        {
+                            var fh = (FileHeader)header;
+                            yield return CreateFilePart(lastMarkHeader!, fh);
+                        }
                         break;
                 }
             }

src/SharpCompress/Common/SevenZip/ArchiveDatabase.cs

@@ -89,7 +89,7 @@ namespace SharpCompress.Common.SevenZip
                 {
                     // v3.13 incorrectly worked with empty folders
                     // v4.07: Loop for skipping empty folders
-                    for (;;)
+                    for (; ; )
                     {
                         if (folderIndex >= _folders.Count)
                         {

src/SharpCompress/Common/SevenZip/ArchiveReader.cs

@@ -90,7 +90,7 @@ namespace SharpCompress.Common.SevenZip
 
         private void WaitAttribute(BlockType attribute)
         {
-            for (;;)
+            for (; ; )
             {
                 BlockType? type = ReadId();
                 if (type == attribute)
@@ -452,7 +452,7 @@ namespace SharpCompress.Common.SevenZip
 #endif
 
                 BlockType? type;
-                for (;;)
+                for (; ; )
                 {
                     type = ReadId();
                     if (type == BlockType.End)
@@ -508,7 +508,7 @@ namespace SharpCompress.Common.SevenZip
                     int index = 0;
                     for (int i = 0; i < numFolders; i++)
                     {
-                        var f = new CFolder {_firstPackStreamId = index};
+                        var f = new CFolder { _firstPackStreamId = index };
                         folders.Add(f);
                         GetNextFolderItem(f);
                         index += f._packStreams.Count;
@@ -539,7 +539,7 @@ namespace SharpCompress.Common.SevenZip
 #endif
                 }
 
-                for (;;)
+                for (; ; )
                 {
                     BlockType? type = ReadId();
                     if (type == BlockType.End)
@@ -580,7 +580,7 @@ namespace SharpCompress.Common.SevenZip
                 numUnpackStreamsInFolders = null;
 
                 BlockType? type;
-                for (;;)
+                for (; ; )
                 {
                     type = ReadId();
                     if (type == BlockType.NumUnpackStream)
@@ -602,7 +602,7 @@ namespace SharpCompress.Common.SevenZip
 #endif
                         continue;
                     }
-                    if (type == BlockType.Crc || type == BlockType.Size)
+                    if (type is BlockType.Crc or BlockType.Size)
                     {
                         break;
                     }
@@ -672,7 +672,7 @@ namespace SharpCompress.Common.SevenZip
 
                 digests = null;
 
-                for (;;)
+                for (; ; )
                 {
                     if (type == BlockType.Crc)
                     {
@@ -755,7 +755,7 @@ namespace SharpCompress.Common.SevenZip
                 unpackSizes = null;
                 digests = null;
 
-                for (;;)
+                for (; ; )
                 {
                     switch (ReadId())
                     {
@@ -791,22 +791,14 @@ namespace SharpCompress.Common.SevenZip
 #endif
             try
             {
-                long dataStartPos;
-                List<long> packSizes;
-                List<uint?> packCrCs;
-                List<CFolder> folders;
-                List<int> numUnpackStreamsInFolders;
-                List<long> unpackSizes;
-                List<uint?> digests;
-
                 ReadStreamsInfo(null,
-                                out dataStartPos,
-                                out packSizes,
-                                out packCrCs,
-                                out folders,
-                                out numUnpackStreamsInFolders,
-                                out unpackSizes,
-                                out digests);
+                                out long dataStartPos,
+                                out List<long> packSizes,
+                                out List<uint?> packCrCs,
+                                out List<CFolder> folders,
+                                out List<int> numUnpackStreamsInFolders,
+                                out List<long> unpackSizes,
+                                out List<uint?> digests);
 
                 dataStartPos += baseOffset;
 
@@ -934,7 +926,7 @@ namespace SharpCompress.Common.SevenZip
                 BitVector antiFileVector = null;
                 int numEmptyStreams = 0;
 
-                for (;;)
+                for (; ; )
                 {
                     type = ReadId();
                     if (type == BlockType.End)
@@ -969,7 +961,7 @@ namespace SharpCompress.Common.SevenZip
 #if DEBUG
                             Log.Write("WinAttributes:");
 #endif
-                            ReadAttributeVector(dataVector, numFiles, delegate(int i, uint? attr)
+                            ReadAttributeVector(dataVector, numFiles, delegate (int i, uint? attr)
                                                                       {
                                                                           // Some third party implementations established an unofficial extension
                                                                           // of the 7z archive format by placing posix file attributes in the high
@@ -1057,7 +1049,7 @@ namespace SharpCompress.Common.SevenZip
 #if DEBUG
                             Log.Write("StartPos:");
 #endif
-                            ReadNumberVector(dataVector, numFiles, delegate(int i, long? startPos)
+                            ReadNumberVector(dataVector, numFiles, delegate (int i, long? startPos)
                                                                    {
                                                                        db._files[i].StartPos = startPos;
 #if DEBUG
@@ -1072,7 +1064,7 @@ namespace SharpCompress.Common.SevenZip
 #if DEBUG
                             Log.Write("CTime:");
 #endif
-                            ReadDateTimeVector(dataVector, numFiles, delegate(int i, DateTime? time)
+                            ReadDateTimeVector(dataVector, numFiles, delegate (int i, DateTime? time)
                                                                      {
                                                                          db._files[i].CTime = time;
 #if DEBUG
@@ -1087,7 +1079,7 @@ namespace SharpCompress.Common.SevenZip
 #if DEBUG
                             Log.Write("ATime:");
 #endif
-                            ReadDateTimeVector(dataVector, numFiles, delegate(int i, DateTime? time)
+                            ReadDateTimeVector(dataVector, numFiles, delegate (int i, DateTime? time)
                                                                      {
                                                                          db._files[i].ATime = time;
 #if DEBUG
@@ -1102,7 +1094,7 @@ namespace SharpCompress.Common.SevenZip
 #if DEBUG
                             Log.Write("MTime:");
 #endif
-                            ReadDateTimeVector(dataVector, numFiles, delegate(int i, DateTime? time)
+                            ReadDateTimeVector(dataVector, numFiles, delegate (int i, DateTime? time)
                                                                      {
                                                                          db._files[i].MTime = time;
 #if DEBUG
@@ -1256,7 +1248,7 @@ namespace SharpCompress.Common.SevenZip
 
             if (nextHeaderOffset > _streamEnding - db._startPositionAfterHeader)
             {
-                throw new IndexOutOfRangeException();
+                throw new InvalidOperationException("nextHeaderOffset is invalid");
             }
 
             _stream.Seek(nextHeaderOffset, SeekOrigin.Current);
@@ -1445,8 +1437,7 @@ namespace SharpCompress.Common.SevenZip
 
         private Stream GetCachedDecoderStream(ArchiveDatabase db, int folderIndex)
         {
-            Stream s;
-            if (!_cachedStreams.TryGetValue(folderIndex, out s))
+            if (!_cachedStreams.TryGetValue(folderIndex, out Stream s))
             {
                 CFolder folderInfo = db._folders[folderIndex];
                 int packStreamIndex = db._folders[folderIndex]._firstPackStreamId;
@@ -1494,7 +1485,7 @@ namespace SharpCompress.Common.SevenZip
             int numItems = allFilesMode
                 ? db._files.Count
                 : indices.Length;
-            
+
             if (numItems == 0)
             {
                 return;
@@ -1526,6 +1517,7 @@ namespace SharpCompress.Common.SevenZip
                 }
             }
 
+            byte[] buffer = null;
             foreach (CExtractFolderInfo efi in extractFolderInfoVector)
             {
                 int startIndex;
@@ -1562,8 +1554,8 @@ namespace SharpCompress.Common.SevenZip
 
                 Stream s = DecoderStreamHelper.CreateDecoderStream(_stream, folderStartPackPos, packSizes,
                                                                    folderInfo, db.PasswordProvider);
-                byte[] buffer = new byte[4 << 10];
-                for (;;)
+                buffer ??= new byte[4 << 10];
+                for (; ; )
                 {
                     int processed = s.Read(buffer, 0, buffer.Length);
                     if (processed == 0)

src/SharpCompress/Common/SevenZip/CFolder.cs

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

src/SharpCompress/Common/SevenZip/CMethodId.cs

@@ -1,6 +1,6 @@
 namespace SharpCompress.Common.SevenZip
 {
-    internal struct CMethodId
+    internal readonly struct CMethodId
     {
         public const ulong K_COPY_ID = 0;
         public const ulong K_LZMA_ID = 0x030101;
@@ -24,9 +24,9 @@
             return _id.GetHashCode();
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
-            return obj is CMethodId && (CMethodId)obj == this;
+            return obj is CMethodId other && Equals(other);
         }
 
         public bool Equals(CMethodId other)

src/SharpCompress/Common/SevenZip/DataReader.cs

@@ -161,7 +161,7 @@ namespace SharpCompress.Common.SevenZip
         {
             int ending = Offset;
 
-            for (;;)
+            for (; ; )
             {
                 if (ending + 2 > _ending)
                 {

src/SharpCompress/Common/SevenZip/SevenZipEntry.cs

@@ -32,7 +32,7 @@ namespace SharpCompress.Common.SevenZip
 
         public override DateTime? ArchivedTime => null;
 
-        public override bool IsEncrypted => false;
+        public override bool IsEncrypted => FilePart.IsEncrypted;
 
         public override bool IsDirectory => FilePart.Header.IsDir;
 

src/SharpCompress/Common/SevenZip/SevenZipFilePart.cs

@@ -84,23 +84,25 @@ namespace SharpCompress.Common.SevenZip
         {
             var coder = Folder!._coders.First();
             switch (coder._methodId._id)
-            {                
+            {
                 case K_LZMA:
                 case K_LZMA2:
-                {
-                    return CompressionType.LZMA;
-                }
+                    {
+                        return CompressionType.LZMA;
+                    }
                 case K_PPMD:
-                {
-                    return CompressionType.PPMd;
-                }
+                    {
+                        return CompressionType.PPMd;
+                    }
                 case K_B_ZIP2:
-                {
-                    return CompressionType.BZip2;
-                }
+                    {
+                        return CompressionType.BZip2;
+                    }
                 default:
                     throw new NotImplementedException();
             }
         }
+
+        internal bool IsEncrypted => Folder!._coders.FindIndex(c => c._methodId._id == CMethodId.K_AES_ID) != -1;
     }
 }

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

@@ -7,7 +7,7 @@ using System.Text;
 
 namespace SharpCompress.Common.Tar.Headers
 {
-    internal class TarHeader
+    internal sealed class TarHeader
     {
         internal static readonly DateTime EPOCH = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
 
@@ -19,11 +19,9 @@ namespace SharpCompress.Common.Tar.Headers
         internal string Name { get; set; }
         internal string LinkName { 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 Mode { get; set; }
+        internal long UserId { get; set; }
+        internal long GroupId { get; set; }
         internal long Size { get; set; }
         internal DateTime LastModifiedTime { get; set; }
         internal EntryType EntryType { get; set; }
@@ -97,7 +95,7 @@ namespace SharpCompress.Common.Tar.Headers
             {
                 numPaddingBytes = BLOCK_SIZE;
             }
-            output.Write(new byte[numPaddingBytes], 0, numPaddingBytes);
+            output.Write(stackalloc byte[numPaddingBytes]);
         }
 
         internal bool Read(BinaryReader reader)
@@ -127,9 +125,12 @@ namespace SharpCompress.Common.Tar.Headers
             EntryType = ReadEntryType(buffer);
             Size = ReadSize(buffer);
 
-            //Mode = ReadASCIIInt32Base8(buffer, 100, 7);
-            //UserId = ReadASCIIInt32Base8(buffer, 108, 7);
-            //GroupId = ReadASCIIInt32Base8(buffer, 116, 7);
+            Mode = ReadAsciiInt64Base8(buffer, 100, 7);
+            if(EntryType == EntryType.Directory) 
+                Mode |= 0b1_000_000_000;
+
+            UserId = ReadAsciiInt64Base8(buffer, 108, 7);
+            GroupId = ReadAsciiInt64Base8(buffer, 116, 7);
             long unixTimeStamp = ReadAsciiInt64Base8(buffer, 136, 11);
             LastModifiedTime = EPOCH.AddSeconds(unixTimeStamp).ToLocalTime();
 
@@ -260,10 +261,16 @@ namespace SharpCompress.Common.Tar.Headers
             return Convert.ToInt64(s);
         }
 
+
+        private static readonly byte[] eightSpaces = {
+            (byte)' ', (byte)' ', (byte)' ', (byte)' ',
+            (byte)' ', (byte)' ', (byte)' ', (byte)' '
+        };
+
         internal static int RecalculateChecksum(byte[] buf)
         {
             // Set default value for checksum. That is 8 spaces.
-            Encoding.UTF8.GetBytes("        ").CopyTo(buf, 148);
+            eightSpaces.CopyTo(buf, 148);
 
             // Calculate checksum
             int headerChecksum = 0;
@@ -276,7 +283,7 @@ namespace SharpCompress.Common.Tar.Headers
 
         internal static int RecalculateAltChecksum(byte[] buf)
         {
-            Encoding.UTF8.GetBytes("        ").CopyTo(buf, 148);
+            eightSpaces.CopyTo(buf, 148);
             int headerChecksum = 0;
             foreach (byte b in buf)
             {

src/SharpCompress/Common/Tar/TarEntry.cs

@@ -44,6 +44,12 @@ 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/Zip/Headers/DirectoryEntryHeader.cs

@@ -32,7 +32,7 @@ namespace SharpCompress.Common.Zip.Headers
             byte[] name = reader.ReadBytes(nameLength);
             byte[] extra = reader.ReadBytes(extraLength);
             byte[] comment = reader.ReadBytes(commentLength);
-            
+
             // According to .ZIP File Format Specification
             //
             // For example: https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
@@ -40,7 +40,7 @@ namespace SharpCompress.Common.Zip.Headers
             // Bit 11: Language encoding flag (EFS).  If this bit is set,
             //         the filename and comment fields for this file
             //         MUST be encoded using UTF-8. (see APPENDIX D)
-            
+
             if (Flags.HasFlag(HeaderFlags.Efs))
             {
                 Name = ArchiveEncoding.DecodeUTF8(name);
@@ -63,6 +63,8 @@ namespace SharpCompress.Common.Zip.Headers
             var zip64ExtraData = Extra.OfType<Zip64ExtendedInformationExtraField>().FirstOrDefault();
             if (zip64ExtraData != null)
             {
+                zip64ExtraData.Process(UncompressedSize, CompressedSize, RelativeOffsetOfEntryHeader, DiskNumberStart);
+
                 if (CompressedSize == uint.MaxValue)
                 {
                     CompressedSize = zip64ExtraData.CompressedSize;

src/SharpCompress/Common/Zip/Headers/LocalEntryHeader.cs

@@ -24,7 +24,7 @@ namespace SharpCompress.Common.Zip.Headers
             ushort extraLength = reader.ReadUInt16();
             byte[] name = reader.ReadBytes(nameLength);
             byte[] extra = reader.ReadBytes(extraLength);
-            
+
             // According to .ZIP File Format Specification
             //
             // For example: https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT
@@ -32,7 +32,7 @@ namespace SharpCompress.Common.Zip.Headers
             // Bit 11: Language encoding flag (EFS).  If this bit is set,
             //         the filename and comment fields for this file
             //         MUST be encoded using UTF-8. (see APPENDIX D)
-            
+
             if (Flags.HasFlag(HeaderFlags.Efs))
             {
                 Name = ArchiveEncoding.DecodeUTF8(name);
@@ -41,7 +41,7 @@ namespace SharpCompress.Common.Zip.Headers
             {
                 Name = ArchiveEncoding.Decode(name);
             }
-            
+
             LoadExtra(extra);
 
             var unicodePathExtra = Extra.FirstOrDefault(u => u.Type == ExtraDataType.UnicodePathExtraField);
@@ -53,6 +53,8 @@ namespace SharpCompress.Common.Zip.Headers
             var zip64ExtraData = Extra.OfType<Zip64ExtendedInformationExtraField>().FirstOrDefault();
             if (zip64ExtraData != null)
             {
+                zip64ExtraData.Process(UncompressedSize, CompressedSize, 0, 0);
+
                 if (CompressedSize == uint.MaxValue)
                 {
                     CompressedSize = zip64ExtraData.CompressedSize;

src/SharpCompress/Common/Zip/Headers/LocalEntryHeaderExtraFactory.cs

@@ -1,6 +1,4 @@
-#nullable disable
-
-using System;
+using System;
 using System.Buffers.Binary;
 using System.Text;
 
@@ -20,13 +18,25 @@ namespace SharpCompress.Common.Zip.Headers
 
     internal class ExtraData
     {
-        internal ExtraDataType Type { get; set; }
-        internal ushort Length { get; set; }
-        internal byte[] DataBytes { get; set; }
+        public ExtraData(ExtraDataType type, ushort length, byte[] dataBytes)
+        {
+            Type = type;
+            Length = length;
+            DataBytes = dataBytes;
+        }
+
+        internal ExtraDataType Type { get; }
+        internal ushort Length { get; }
+        internal byte[] DataBytes { get; }
     }
 
-    internal class ExtraUnicodePathExtraField : ExtraData
+    internal sealed class ExtraUnicodePathExtraField : ExtraData
     {
+        public ExtraUnicodePathExtraField(ExtraDataType type, ushort length, byte[] dataBytes)
+            : base(type, length, dataBytes)
+        {
+        }
+
         internal byte Version => DataBytes[0];
 
         internal byte[] NameCrc32
@@ -51,70 +61,79 @@ namespace SharpCompress.Common.Zip.Headers
         }
     }
 
-    internal class Zip64ExtendedInformationExtraField : ExtraData
+    internal sealed class Zip64ExtendedInformationExtraField : ExtraData
     {
-
         public Zip64ExtendedInformationExtraField(ExtraDataType type, ushort length, byte[] dataBytes)
+            : base(type, length, dataBytes)
         {
-            Type = type;
-            Length = length;
-            DataBytes = dataBytes;
-            Process();
         }
 
-        //From the spec values are only in the extradata if the standard
-        //value is set to 0xFFFF, but if one of the sizes are present, both are.
-        //Hence if length == 4 volume only
-        //      if length == 8 offset only
-        //      if length == 12 offset + volume
-        //      if length == 16 sizes only
-        //      if length == 20 sizes + volume
-        //      if length == 24 sizes + offset
-        //      if length == 28 everything.
-        //It is unclear how many of these are used in the wild.
-
-        private void Process()
+        // From the spec, values are only in the extradata if the standard
+        // value is set to 0xFFFFFFFF (or 0xFFFF for the Disk Start Number).
+        // Values, if present, must appear in the following order:
+        // - Original Size
+        // - Compressed Size
+        // - Relative Header Offset
+        // - Disk Start Number
+        public void Process(long uncompressedFileSize, long compressedFileSize, long relativeHeaderOffset, ushort diskNumber)
         {
-            switch (DataBytes.Length)
+            var bytesRequired = ((uncompressedFileSize == uint.MaxValue) ? 8 : 0)
+                + ((compressedFileSize == uint.MaxValue) ? 8 : 0)
+                + ((relativeHeaderOffset == uint.MaxValue) ? 8 : 0)
+                + ((diskNumber == ushort.MaxValue) ? 4 : 0);
+            var currentIndex = 0;
+
+            if (bytesRequired > DataBytes.Length)
             {
-                case 4:
-                    VolumeNumber = BinaryPrimitives.ReadUInt32LittleEndian(DataBytes);
-                    return;
-                case 8:
-                    RelativeOffsetOfEntryHeader = BinaryPrimitives.ReadInt64LittleEndian(DataBytes);
-                    return;
-                case 12:
-                    RelativeOffsetOfEntryHeader = BinaryPrimitives.ReadInt64LittleEndian(DataBytes);
-                    VolumeNumber = BinaryPrimitives.ReadUInt32LittleEndian(DataBytes.AsSpan(8));
-                    return;
-                case 16:
-                    UncompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes);
-                    CompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(8));
-                    return;
-                case 20:
-                    UncompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes);
-                    CompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(8));
-                    VolumeNumber = BinaryPrimitives.ReadUInt32LittleEndian(DataBytes.AsSpan(16));
-                    return;
-                case 24:
-                    UncompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes);
-                    CompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(8));
-                    RelativeOffsetOfEntryHeader = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(16));
-                    return;
-                case 28:
-                    UncompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes);
-                    CompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(8));
-                    RelativeOffsetOfEntryHeader = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(16));
-                    VolumeNumber = BinaryPrimitives.ReadUInt32LittleEndian(DataBytes.AsSpan(24));
-                    return;
-                default:
-                throw new ArchiveException("Unexpected size of of Zip64 extended information extra field");
+                throw new ArchiveException("Zip64 extended information extra field is not large enough for the required information");
+            }
+
+            if (uncompressedFileSize == uint.MaxValue)
+            {
+                UncompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(currentIndex));
+                currentIndex += 8;
+            }
+
+            if (compressedFileSize == uint.MaxValue)
+            {
+                CompressedSize = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(currentIndex));
+                currentIndex += 8;
+            }
+
+            if (relativeHeaderOffset == uint.MaxValue)
+            {
+                RelativeOffsetOfEntryHeader = BinaryPrimitives.ReadInt64LittleEndian(DataBytes.AsSpan(currentIndex));
+                currentIndex += 8;
+            }
+
+            if (diskNumber == ushort.MaxValue)
+            {
+                VolumeNumber = BinaryPrimitives.ReadUInt32LittleEndian(DataBytes.AsSpan(currentIndex));
             }
         }
 
+        /// <summary>
+        /// Uncompressed file size. Only valid after <see cref="Process(long, long, long, ushort)"/> has been called and if the
+        /// original entry header had a corresponding 0xFFFFFFFF value.
+        /// </summary>
         public long UncompressedSize { get; private set; }
+
+        /// <summary>
+        /// Compressed file size. Only valid after <see cref="Process(long, long, long, ushort)"/> has been called and if the
+        /// original entry header had a corresponding 0xFFFFFFFF value.
+        /// </summary>
         public long CompressedSize { get; private set; }
+
+        /// <summary>
+        /// Relative offset of the entry header. Only valid after <see cref="Process(long, long, long, ushort)"/> has been called and if the
+        /// original entry header had a corresponding 0xFFFFFFFF value.
+        /// </summary>
         public long RelativeOffsetOfEntryHeader { get; private set; }
+
+        /// <summary>
+        /// Volume number. Only valid after <see cref="Process(long, long, long, ushort)"/> has been called and if the
+        /// original entry header had a corresponding 0xFFFF value.
+        /// </summary>
         public uint VolumeNumber { get; private set; }
     }
 
@@ -122,30 +141,12 @@ namespace SharpCompress.Common.Zip.Headers
     {
         internal static ExtraData Create(ExtraDataType type, ushort length, byte[] extraData)
         {
-            switch (type)
+            return type switch
             {
-                case ExtraDataType.UnicodePathExtraField:
-                    return new ExtraUnicodePathExtraField
-                           {
-                               Type = type,
-                               Length = length,
-                               DataBytes = extraData
-                           };
-                case ExtraDataType.Zip64ExtendedInformationExtraField:
-                    return new Zip64ExtendedInformationExtraField
-                            (
-                                type,
-                                length,
-                                extraData
-                           );
-                default:
-                    return new ExtraData
-                           {
-                               Type = type,
-                               Length = length,
-                               DataBytes = extraData
-                           };
-            }
+                ExtraDataType.UnicodePathExtraField => new ExtraUnicodePathExtraField(type, length, extraData),
+                ExtraDataType.Zip64ExtendedInformationExtraField => new Zip64ExtendedInformationExtraField(type, length, extraData),
+                _ => new ExtraData(type, length, extraData)
+            };
         }
     }
 }

src/SharpCompress/Common/Zip/Headers/ZipFileEntry.cs

@@ -20,7 +20,7 @@ namespace SharpCompress.Common.Zip.Headers
         {
             get
             {
-                if (Name.EndsWith("/"))
+                if (Name.EndsWith('/'))
                 {
                     return true;
                 }
@@ -28,7 +28,7 @@ namespace SharpCompress.Common.Zip.Headers
                 //.NET Framework 4.5 : System.IO.Compression::CreateFromDirectory() probably writes backslashes to headers
                 return CompressedSize == 0
                        && UncompressedSize == 0
-                       && Name.EndsWith("\\");
+                       && Name.EndsWith('\\');
             }
         }
 
@@ -105,6 +105,6 @@ namespace SharpCompress.Common.Zip.Headers
 
         internal ZipFilePart Part { get; set; }
 
-        internal bool IsZip64 => CompressedSize == uint.MaxValue;
+        internal bool IsZip64 => CompressedSize >= uint.MaxValue;
     }
 }

src/SharpCompress/Common/Zip/PkwareTraditionalEncryptionData.cs

@@ -7,7 +7,7 @@ namespace SharpCompress.Common.Zip
     internal class PkwareTraditionalEncryptionData
     {
         private static readonly CRC32 CRC32 = new CRC32();
-        private readonly UInt32[] _keys = {0x12345678, 0x23456789, 0x34567890};
+        private readonly UInt32[] _keys = { 0x12345678, 0x23456789, 0x34567890 };
         private readonly ArchiveEncoding _archiveEncoding;
 
         private PkwareTraditionalEncryptionData(string password, ArchiveEncoding archiveEncoding)

src/SharpCompress/Common/Zip/SeekableZipHeaderFactory.cs

@@ -8,7 +8,10 @@ namespace SharpCompress.Common.Zip
 {
     internal sealed class SeekableZipHeaderFactory : ZipHeaderFactory
     {
-        private const int MAX_ITERATIONS_FOR_DIRECTORY_HEADER = 4096;
+        private const int MINIMUM_EOCD_LENGTH = 22;
+        private const int ZIP64_EOCD_LENGTH = 20;
+        // Comment may be within 64kb + structure 22 bytes
+        private const int MAX_SEARCH_LENGTH_FOR_EOCD = 65557;
         private bool _zip64;
 
         internal SeekableZipHeaderFactory(string? password, ArchiveEncoding archiveEncoding)
@@ -20,14 +23,24 @@ namespace SharpCompress.Common.Zip
         {
             var reader = new BinaryReader(stream);
 
-            SeekBackToHeader(stream, reader, DIRECTORY_END_HEADER_BYTES);
+            SeekBackToHeader(stream, reader);
+
+            var eocd_location = stream.Position;
             var entry = new DirectoryEndHeader();
             entry.Read(reader);
 
             if (entry.IsZip64)
             {
                 _zip64 = true;
-                SeekBackToHeader(stream, reader, ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR);
+
+                // ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR should be before the EOCD
+                stream.Seek(eocd_location - ZIP64_EOCD_LENGTH - 4, SeekOrigin.Begin);
+                uint zip64_locator = reader.ReadUInt32();
+                if (zip64_locator != ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR)
+                {
+                    throw new ArchiveException("Failed to locate the Zip64 Directory Locator");
+                }
+
                 var zip64Locator = new Zip64DirectoryEndLocatorHeader();
                 zip64Locator.Read(reader);
 
@@ -73,27 +86,50 @@ namespace SharpCompress.Common.Zip
             }
         }
 
-        private static void SeekBackToHeader(Stream stream, BinaryReader reader, uint headerSignature)
+        private static bool IsMatch(byte[] haystack, int position, byte[] needle)
         {
-            long offset = 0;
-            uint signature;
-            int iterationCount = 0;
-            do
+            for (int i = 0; i < needle.Length; i++)
             {
-                if ((stream.Length + offset) - 4 < 0)
+                if (haystack[position + i] != needle[i])
                 {
-                    throw new ArchiveException("Failed to locate the Zip Header");
-                }
-                stream.Seek(offset - 4, SeekOrigin.End);
-                signature = reader.ReadUInt32();
-                offset--;
-                iterationCount++;
-                if (iterationCount > MAX_ITERATIONS_FOR_DIRECTORY_HEADER)
-                {
-                    throw new ArchiveException("Could not find Zip file Directory at the end of the file.  File may be corrupted.");
+                    return false;
                 }
             }
-            while (signature != headerSignature);
+
+            return true;
+        }
+        private static void SeekBackToHeader(Stream stream, BinaryReader reader)
+        {
+            // Minimum EOCD length
+            if (stream.Length < MINIMUM_EOCD_LENGTH)
+            {
+                throw new ArchiveException("Could not find Zip file Directory at the end of the file. File may be corrupted.");
+            }
+
+            int len = stream.Length < MAX_SEARCH_LENGTH_FOR_EOCD ? (int)stream.Length : MAX_SEARCH_LENGTH_FOR_EOCD;
+            // We search for marker in reverse to find the first occurance
+            byte[] needle = { 0x06, 0x05, 0x4b, 0x50 };
+
+            stream.Seek(-len, SeekOrigin.End);
+
+            byte[] seek = reader.ReadBytes(len);
+
+            // Search in reverse
+            Array.Reverse(seek);
+
+            // don't exclude the minimum eocd region, otherwise you fail to locate the header in empty zip files
+            var max_search_area = len; // - MINIMUM_EOCD_LENGTH;
+
+            for (int pos_from_end = 0; pos_from_end < max_search_area; ++pos_from_end)
+            {
+                if (IsMatch(seek, pos_from_end, needle))
+                {
+                    stream.Seek(-pos_from_end, SeekOrigin.End);
+                    return;
+                }
+            }
+
+            throw new ArchiveException("Failed to locate the Zip Header");
         }
 
         internal LocalEntryHeader GetLocalHeader(Stream stream, DirectoryEntryHeader directoryEntryHeader)

src/SharpCompress/Common/Zip/StreamingZipFilePart.cs

@@ -42,7 +42,7 @@ namespace SharpCompress.Common.Zip
             if (Header.HasData && !Skipped)
             {
                 _decompressionStream ??= GetCompressedStream();
-                
+
                 _decompressionStream.Skip();
 
                 if (_decompressionStream is DeflateStream deflateStream)

src/SharpCompress/Common/Zip/StreamingZipHeaderFactory.cs

@@ -49,7 +49,10 @@ namespace SharpCompress.Common.Zip
                 _lastEntryHeader = null;
                 uint headerBytes = reader.ReadUInt32();
                 header = ReadHeader(headerBytes, reader);
-                if (header is null) { yield break; }
+                if (header is null)
+                {
+                    yield break;
+                }
 
                 //entry could be zero bytes so we need to know that.
                 if (header.ZipHeaderType == ZipHeaderType.LocalEntry)
@@ -57,11 +60,11 @@ namespace SharpCompress.Common.Zip
                     var local_header = ((LocalEntryHeader)header);
 
                     // If we have CompressedSize, there is data to be read
-                    if( local_header.CompressedSize > 0 )
+                    if (local_header.CompressedSize > 0)
                     {
                         header.HasData = true;
                     } // Check if zip is streaming ( Length is 0 and is declared in PostDataDescriptor )
-                    else if( local_header.Flags.HasFlag(HeaderFlags.UsePostDataDescriptor) )
+                    else if (local_header.Flags.HasFlag(HeaderFlags.UsePostDataDescriptor))
                     {
                         bool isRecording = rewindableStream.IsRecording;
                         if (!isRecording)

src/SharpCompress/Common/Zip/WinzipAesCryptoStream.cs

@@ -75,7 +75,7 @@ namespace SharpCompress.Common.Zip
             if (disposing)
             {
                 //read out last 10 auth bytes
-                var ten = new byte[10];
+                Span<byte> ten = stackalloc byte[10];
                 _stream.ReadFully(ten);
                 _stream.Dispose();
             }

src/SharpCompress/Common/Zip/WinzipAesEncryptionData.cs

@@ -33,8 +33,10 @@ namespace SharpCompress.Common.Zip
 
         private int KeySizeInBytes
         {
-            get { return KeyLengthInBytes(_keySize);
-}
+            get
+            {
+                return KeyLengthInBytes(_keySize);
+            }
         }
 
         internal static int KeyLengthInBytes(WinzipAesKeySize keySize)

src/SharpCompress/Common/Zip/ZipEntry.cs

@@ -27,33 +27,33 @@ namespace SharpCompress.Common.Zip
                 switch (_filePart.Header.CompressionMethod)
                 {
                     case ZipCompressionMethod.BZip2:
-                    {
-                        return CompressionType.BZip2;
-                    }
+                        {
+                            return CompressionType.BZip2;
+                        }
                     case ZipCompressionMethod.Deflate:
-                    {
-                        return CompressionType.Deflate;
-                    }
+                        {
+                            return CompressionType.Deflate;
+                        }
                     case ZipCompressionMethod.Deflate64:
-                    {
-                        return CompressionType.Deflate64;
-                    }
+                        {
+                            return CompressionType.Deflate64;
+                        }
                     case ZipCompressionMethod.LZMA:
-                    {
-                        return CompressionType.LZMA;
-                    }
+                        {
+                            return CompressionType.LZMA;
+                        }
                     case ZipCompressionMethod.PPMd:
-                    {
-                        return CompressionType.PPMd;
-                    }
+                        {
+                            return CompressionType.PPMd;
+                        }
                     case ZipCompressionMethod.None:
-                    {
-                        return CompressionType.None;
-                    }
+                        {
+                            return CompressionType.None;
+                        }
                     default:
-                    {
-                        return CompressionType.Unknown;
-                    }
+                        {
+                            return CompressionType.Unknown;
+                        }
                 }
             }
         }

src/SharpCompress/Common/Zip/ZipFilePart.cs

@@ -60,72 +60,72 @@ namespace SharpCompress.Common.Zip
             switch (method)
             {
                 case ZipCompressionMethod.None:
-                {
-                    return stream;
-                }
+                    {
+                        return stream;
+                    }
                 case ZipCompressionMethod.Deflate:
-                {
-                    return new DeflateStream(stream, CompressionMode.Decompress);
-                }
+                    {
+                        return new DeflateStream(stream, CompressionMode.Decompress);
+                    }
                 case ZipCompressionMethod.Deflate64:
-                {
-                    return new Deflate64Stream(stream, CompressionMode.Decompress);
-                }
+                    {
+                        return new Deflate64Stream(stream, CompressionMode.Decompress);
+                    }
                 case ZipCompressionMethod.BZip2:
-                {
-                    return new BZip2Stream(stream, CompressionMode.Decompress, false);
-                }
+                    {
+                        return new BZip2Stream(stream, CompressionMode.Decompress, false);
+                    }
                 case ZipCompressionMethod.LZMA:
-                {
-                    if (FlagUtility.HasFlag(Header.Flags, HeaderFlags.Encrypted))
                     {
-                        throw new NotSupportedException("LZMA with pkware encryption.");
+                        if (FlagUtility.HasFlag(Header.Flags, HeaderFlags.Encrypted))
+                        {
+                            throw new NotSupportedException("LZMA with pkware encryption.");
+                        }
+                        var reader = new BinaryReader(stream);
+                        reader.ReadUInt16(); //LZMA version
+                        var props = new byte[reader.ReadUInt16()];
+                        reader.Read(props, 0, props.Length);
+                        return new LzmaStream(props, stream,
+                                              Header.CompressedSize > 0 ? Header.CompressedSize - 4 - props.Length : -1,
+                                              FlagUtility.HasFlag(Header.Flags, HeaderFlags.Bit1)
+                                                  ? -1
+                                                  : (long)Header.UncompressedSize);
                     }
-                    var reader = new BinaryReader(stream);
-                    reader.ReadUInt16(); //LZMA version
-                    var props = new byte[reader.ReadUInt16()];
-                    reader.Read(props, 0, props.Length);
-                    return new LzmaStream(props, stream,
-                                          Header.CompressedSize > 0 ? Header.CompressedSize - 4 - props.Length : -1,
-                                          FlagUtility.HasFlag(Header.Flags, HeaderFlags.Bit1)
-                                              ? -1
-                                              : (long)Header.UncompressedSize);
-                }
                 case ZipCompressionMethod.PPMd:
-                {
-                    var props = new byte[2];
-                    stream.ReadFully(props);
-                    return new PpmdStream(new PpmdProperties(props), stream, false);
-                }
+                    {
+                        Span<byte> props = stackalloc byte[2];
+                        stream.ReadFully(props);
+                        return new PpmdStream(new PpmdProperties(props), stream, false);
+                    }
                 case ZipCompressionMethod.WinzipAes:
-                {
-                    ExtraData data = Header.Extra.Where(x => x.Type == ExtraDataType.WinZipAes).SingleOrDefault();
-                    if (data is null)
                     {
-                        throw new InvalidFormatException("No Winzip AES extra data found.");
-                    }
-                    if (data.Length != 7)
-                    {
-                        throw new InvalidFormatException("Winzip data length is not 7.");
-                    }
-                    ushort compressedMethod = BinaryPrimitives.ReadUInt16LittleEndian(data.DataBytes);
+                        ExtraData? data = Header.Extra.SingleOrDefault(x => x.Type == ExtraDataType.WinZipAes);
+                        if (data is null)
+                        {
+                            throw new InvalidFormatException("No Winzip AES extra data found.");
+                        }
+                        if (data.Length != 7)
+                        {
+                            throw new InvalidFormatException("Winzip data length is not 7.");
+                        }
+                        ushort compressedMethod = BinaryPrimitives.ReadUInt16LittleEndian(data.DataBytes);
 
-                    if (compressedMethod != 0x01 && compressedMethod != 0x02)
-                    {
-                        throw new InvalidFormatException("Unexpected vendor version number for WinZip AES metadata");
-                    }
+                        if (compressedMethod != 0x01 && compressedMethod != 0x02)
+                        {
+                            throw new InvalidFormatException("Unexpected vendor version number for WinZip AES metadata");
+                        }
 
-                    ushort vendorId = BinaryPrimitives.ReadUInt16LittleEndian(data.DataBytes.AsSpan(2));
-                    if (vendorId != 0x4541)
-                    {
-                        throw new InvalidFormatException("Unexpected vendor ID for WinZip AES metadata");
+                        ushort vendorId = BinaryPrimitives.ReadUInt16LittleEndian(data.DataBytes.AsSpan(2));
+                        if (vendorId != 0x4541)
+                        {
+                            throw new InvalidFormatException("Unexpected vendor ID for WinZip AES metadata");
+                        }
+                        return CreateDecompressionStream(stream, (ZipCompressionMethod)BinaryPrimitives.ReadUInt16LittleEndian(data.DataBytes.AsSpan(5)));
                     }
-                    return CreateDecompressionStream(stream, (ZipCompressionMethod)BinaryPrimitives.ReadUInt16LittleEndian(data.DataBytes.AsSpan(5)));
-                }
                 default:
-                {
-                    throw new NotSupportedException("CompressionMethod: " + Header.CompressionMethod);
-                }
+                    {
+                        throw new NotSupportedException("CompressionMethod: " + Header.CompressionMethod);
+                    }
             }
         }
 
@@ -159,23 +159,23 @@ namespace SharpCompress.Common.Zip
                     case ZipCompressionMethod.BZip2:
                     case ZipCompressionMethod.LZMA:
                     case ZipCompressionMethod.PPMd:
-                    {
-                        return new PkwareTraditionalCryptoStream(plainStream, Header.ComposeEncryptionData(plainStream), CryptoMode.Decrypt);
-                    }
+                        {
+                            return new PkwareTraditionalCryptoStream(plainStream, Header.ComposeEncryptionData(plainStream), CryptoMode.Decrypt);
+                        }
 
                     case ZipCompressionMethod.WinzipAes:
-                    {
-                        if (Header.WinzipAesEncryptionData != null)
                         {
-                            return new WinzipAesCryptoStream(plainStream, Header.WinzipAesEncryptionData, Header.CompressedSize - 10);
+                            if (Header.WinzipAesEncryptionData != null)
+                            {
+                                return new WinzipAesCryptoStream(plainStream, Header.WinzipAesEncryptionData, Header.CompressedSize - 10);
+                            }
+                            return plainStream;
                         }
-                        return plainStream;
-                    }
 
                     default:
-                    {
-                        throw new ArgumentOutOfRangeException();
-                    }
+                        {
+                            throw new InvalidOperationException("Header.CompressionMethod is invalid");
+                        }
 
                 }
             }

src/SharpCompress/Common/Zip/ZipHeaderFactory.cs

@@ -35,20 +35,20 @@ namespace SharpCompress.Common.Zip
             switch (headerBytes)
             {
                 case ENTRY_HEADER_BYTES:
-                {
-                    var entryHeader = new LocalEntryHeader(_archiveEncoding);
-                    entryHeader.Read(reader);
-                    LoadHeader(entryHeader, reader.BaseStream);
+                    {
+                        var entryHeader = new LocalEntryHeader(_archiveEncoding);
+                        entryHeader.Read(reader);
+                        LoadHeader(entryHeader, reader.BaseStream);
 
-                    _lastEntryHeader = entryHeader;
-                    return entryHeader;
-                }
+                        _lastEntryHeader = entryHeader;
+                        return entryHeader;
+                    }
                 case DIRECTORY_START_HEADER_BYTES:
-                {
-                    var entry = new DirectoryEntryHeader(_archiveEncoding);
-                    entry.Read(reader);
-                    return entry;
-                }
+                    {
+                        var entry = new DirectoryEntryHeader(_archiveEncoding);
+                        entry.Read(reader);
+                        return entry;
+                    }
                 case POST_DATA_DESCRIPTOR:
                     {
                         if (FlagUtility.HasFlag(_lastEntryHeader!.Flags, HeaderFlags.UsePostDataDescriptor))
@@ -129,7 +129,7 @@ namespace SharpCompress.Common.Zip
 
                 if (entryHeader.CompressionMethod == ZipCompressionMethod.WinzipAes)
                 {
-                    ExtraData data = entryHeader.Extra.SingleOrDefault(x => x.Type == ExtraDataType.WinZipAes);
+                    ExtraData? data = entryHeader.Extra.SingleOrDefault(x => x.Type == ExtraDataType.WinZipAes);
                     if (data != null)
                     {
                         var keySize = (WinzipAesKeySize)data.DataBytes[4];

src/SharpCompress/Compressors/ADC/ADCBase.cs

@@ -52,32 +52,24 @@ namespace SharpCompress.Compressors.ADC
 
         private static int GetChunkSize(byte byt)
         {
-            switch (GetChunkType(byt))
+            return GetChunkType(byt) switch
             {
-                case PLAIN:
-                    return (byt & 0x7F) + 1;
-                case TWO_BYTE:
-                    return ((byt & 0x3F) >> 2) + 3;
-                case THREE_BYTE:
-                    return (byt & 0x3F) + 4;
-                default:
-                    return -1;
-            }
+                PLAIN => (byt & 0x7F) + 1,
+                TWO_BYTE => ((byt & 0x3F) >> 2) + 3,
+                THREE_BYTE => (byt & 0x3F) + 4,
+                _ => -1,
+            };
         }
 
         private static int GetOffset(ReadOnlySpan<byte> chunk)
         {
-            switch (GetChunkType(chunk[0]))
+            return GetChunkType(chunk[0]) switch
             {
-                case PLAIN:
-                    return 0;
-                case TWO_BYTE:
-                    return ((chunk[0] & 0x03) << 8) + chunk[1];
-                case THREE_BYTE:
-                    return (chunk[1] << 8) + chunk[2];
-                default:
-                    return -1;
-            }
+                PLAIN => 0,
+                TWO_BYTE => ((chunk[0] & 0x03) << 8) + chunk[1],
+                THREE_BYTE => (chunk[1] << 8) + chunk[2],
+                _ => -1,
+            };
         }
 
         /// <summary>

src/SharpCompress/Compressors/BZip2/BZip2Stream.cs

@@ -1,8 +1,9 @@
-using System.IO;
+using System;
+using System.IO;
 
 namespace SharpCompress.Compressors.BZip2
 {
-    public class BZip2Stream : Stream
+    public sealed class BZip2Stream : Stream
     {
         private readonly Stream stream;
         private bool isDisposed;
@@ -82,6 +83,20 @@ namespace SharpCompress.Compressors.BZip2
             stream.SetLength(value);
         }
 
+#if !NETFRAMEWORK && !NETSTANDARD2_0
+
+        public override int Read(Span<byte> buffer)
+        {
+            return stream.Read(buffer);
+        }
+
+        public override void Write(ReadOnlySpan<byte> buffer)
+        {
+            stream.Write(buffer);
+        }
+
+#endif
+
         public override void Write(byte[] buffer, int offset, int count)
         {
             stream.Write(buffer, offset, count);
@@ -108,4 +123,4 @@ namespace SharpCompress.Compressors.BZip2
             return true;
         }
     }
-}
+}

src/SharpCompress/Compressors/BZip2/CBZip2InputStream.cs

@@ -1,5 +1,6 @@
 #nullable disable
 
+using System;
 using System.IO;
 
 /*
@@ -835,7 +836,7 @@ namespace SharpCompress.Compressors.BZip2
 
         private void SetupBlock()
         {
-            int[] cftab = new int[257];
+            Span<int> cftab = stackalloc int[257];
             char ch;
 
             cftab[0] = 0;
@@ -854,7 +855,6 @@ namespace SharpCompress.Compressors.BZip2
                 tt[cftab[ch]] = i;
                 cftab[ch]++;
             }
-            cftab = null;
 
             tPos = tt[origPtr];
 

src/SharpCompress/Compressors/BZip2/CBZip2OutputStream.cs

@@ -1,4 +1,5 @@
-using System.IO;
+using System;
+using System.IO;
 
 /*
  * Copyright 2001,2004-2005 The Apache Software Foundation
@@ -88,9 +89,9 @@ namespace SharpCompress.Compressors.BZip2
             int nNodes, nHeap, n1, n2, i, j, k;
             bool tooLong;
 
-            int[] heap = new int[BZip2Constants.MAX_ALPHA_SIZE + 2];
-            int[] weight = new int[BZip2Constants.MAX_ALPHA_SIZE * 2];
-            int[] parent = new int[BZip2Constants.MAX_ALPHA_SIZE * 2];
+            Span<int> heap = stackalloc int[BZip2Constants.MAX_ALPHA_SIZE + 2]; // 1040 bytes
+            Span<int> weight = stackalloc int[BZip2Constants.MAX_ALPHA_SIZE * 2];  // 1040 bytes
+            Span<int> parent = stackalloc int[BZip2Constants.MAX_ALPHA_SIZE * 2];  // 1040 bytes
 
             for (i = 0; i < alphaSize; i++)
             {
@@ -603,14 +604,7 @@ namespace SharpCompress.Compressors.BZip2
             while (bsLive > 0)
             {
                 int ch = (bsBuff >> 24);
-                try
-                {
-                    bsStream.WriteByte((byte)ch); // write 8-bit
-                }
-                catch (IOException e)
-                {
-                    throw e;
-                }
+                bsStream.WriteByte((byte)ch); // write 8-bit
                 bsBuff <<= 8;
                 bsLive -= 8;
                 bytesOut++;
@@ -622,14 +616,7 @@ namespace SharpCompress.Compressors.BZip2
             while (bsLive >= 8)
             {
                 int ch = (bsBuff >> 24);
-                try
-                {
-                    bsStream.WriteByte((byte)ch); // write 8-bit
-                }
-                catch (IOException e)
-                {
-                    throw e;
-                }
+                bsStream.WriteByte((byte)ch); // write 8-bit
                 bsBuff <<= 8;
                 bsLive -= 8;
                 bytesOut++;
@@ -1328,8 +1315,8 @@ namespace SharpCompress.Compressors.BZip2
         private void MainSort()
         {
             int i, j, ss, sb;
-            int[] runningOrder = new int[256];
-            int[] copy = new int[256];
+            Span<int> runningOrder = stackalloc int[256];
+            Span<int> copy = stackalloc int[256];
             bool[] bigDone = new bool[256];
             int c1, c2;
             int numQSorted;

src/SharpCompress/Compressors/Deflate/CRC32.cs

@@ -189,7 +189,7 @@ namespace SharpCompress.Compressors.Deflate
 
         // pre-initialize the crc table for speed of lookup.
 
-        private uint gf2_matrix_times(uint[] matrix, uint vec)
+        private uint gf2_matrix_times(ReadOnlySpan<uint> matrix, uint vec)
         {
             uint sum = 0;
             int i = 0;
@@ -205,7 +205,7 @@ namespace SharpCompress.Compressors.Deflate
             return sum;
         }
 
-        private void gf2_matrix_square(uint[] square, uint[] mat)
+        private void gf2_matrix_square(Span<uint> square, Span<uint> mat)
         {
             for (int i = 0; i < 32; i++)
             {
@@ -225,8 +225,8 @@ namespace SharpCompress.Compressors.Deflate
         /// <param name="length">the length of data the CRC value was calculated on</param>
         public void Combine(int crc, int length)
         {
-            var even = new uint[32]; // even-power-of-two zeros operator
-            var odd = new uint[32]; // odd-power-of-two zeros operator
+            Span<uint> even = stackalloc uint[32]; // even-power-of-two zeros operator
+            Span<uint> odd = stackalloc uint[32]; // odd-power-of-two zeros operator
 
             if (length == 0)
             {

src/SharpCompress/Compressors/Deflate/DeflateManager.cs

@@ -70,6 +70,8 @@
 
 using System;
 
+using SharpCompress.Algorithms;
+
 namespace SharpCompress.Compressors.Deflate
 {
     internal sealed partial class DeflateManager
@@ -1685,7 +1687,7 @@ namespace SharpCompress.Compressors.Deflate
             Rfc1950BytesEmitted = false;
 
             status = (WantRfc1950HeaderBytes) ? INIT_STATE : BUSY_STATE;
-            _codec._Adler32 = Adler.Adler32(0, null, 0, 0);
+            _codec._adler32 = 1;
 
             last_flush = (int)FlushType.None;
 
@@ -1763,7 +1765,7 @@ namespace SharpCompress.Compressors.Deflate
                 throw new ZlibException("Stream error.");
             }
 
-            _codec._Adler32 = Adler.Adler32(_codec._Adler32, dictionary, 0, dictionary.Length);
+            _codec._adler32 = Adler32.Calculate(_codec._adler32, dictionary);
 
             if (length < MIN_MATCH)
             {
@@ -1850,12 +1852,12 @@ namespace SharpCompress.Compressors.Deflate
                     ////putShortMSB((int)(SharedUtils.URShift(_codec._Adler32, 16)));
                     //putShortMSB((int)((UInt64)_codec._Adler32 >> 16));
                     //putShortMSB((int)(_codec._Adler32 & 0xffff));
-                    pending[pendingCount++] = (byte)((_codec._Adler32 & 0xFF000000) >> 24);
-                    pending[pendingCount++] = (byte)((_codec._Adler32 & 0x00FF0000) >> 16);
-                    pending[pendingCount++] = (byte)((_codec._Adler32 & 0x0000FF00) >> 8);
-                    pending[pendingCount++] = (byte)(_codec._Adler32 & 0x000000FF);
+                    pending[pendingCount++] = (byte)((_codec._adler32 & 0xFF000000) >> 24);
+                    pending[pendingCount++] = (byte)((_codec._adler32 & 0x00FF0000) >> 16);
+                    pending[pendingCount++] = (byte)((_codec._adler32 & 0x0000FF00) >> 8);
+                    pending[pendingCount++] = (byte)(_codec._adler32 & 0x000000FF);
                 }
-                _codec._Adler32 = Adler.Adler32(0, null, 0, 0);
+                _codec._adler32 = 1;
             }
 
             // Flush as much pending output as possible
@@ -1968,10 +1970,10 @@ namespace SharpCompress.Compressors.Deflate
             }
 
             // Write the zlib trailer (adler32)
-            pending[pendingCount++] = (byte)((_codec._Adler32 & 0xFF000000) >> 24);
-            pending[pendingCount++] = (byte)((_codec._Adler32 & 0x00FF0000) >> 16);
-            pending[pendingCount++] = (byte)((_codec._Adler32 & 0x0000FF00) >> 8);
-            pending[pendingCount++] = (byte)(_codec._Adler32 & 0x000000FF);
+            pending[pendingCount++] = (byte)((_codec._adler32 & 0xFF000000) >> 24);
+            pending[pendingCount++] = (byte)((_codec._adler32 & 0x00FF0000) >> 16);
+            pending[pendingCount++] = (byte)((_codec._adler32 & 0x0000FF00) >> 8);
+            pending[pendingCount++] = (byte)(_codec._adler32 & 0x000000FF);
 
             //putShortMSB((int)(SharedUtils.URShift(_codec._Adler32, 16)));
             //putShortMSB((int)(_codec._Adler32 & 0xffff));

src/SharpCompress/Compressors/Deflate/GZipStream.cs

@@ -37,10 +37,9 @@ namespace SharpCompress.Compressors.Deflate
     {
         internal static readonly DateTime UNIX_EPOCH = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
 
-        public DateTime? LastModified { get; set; }
-
         private string? _comment;
         private string? _fileName;
+        private DateTime? _lastModified;
 
         internal ZlibBaseStream BaseStream;
         private bool _disposed;
@@ -274,6 +273,7 @@ namespace SharpCompress.Compressors.Deflate
                 _firstReadDone = true;
                 FileName = BaseStream._GzipFileName;
                 Comment = BaseStream._GzipComment;
+                LastModified = BaseStream._GzipMtime;
             }
             return n;
         }
@@ -358,6 +358,20 @@ namespace SharpCompress.Compressors.Deflate
             }
         }
 
+
+        public DateTime? LastModified
+        {
+            get => _lastModified;
+            set
+            {
+                if (_disposed)
+                {
+                    throw new ObjectDisposedException(nameof(GZipStream));
+                }
+                _lastModified = value;
+            }
+        }
+
         public string? FileName
         {
             get => _fileName;
@@ -372,28 +386,19 @@ namespace SharpCompress.Compressors.Deflate
                 {
                     return;
                 }
-                if (_fileName.Contains("/"))
+                if (_fileName.Contains('/'))
                 {
                     _fileName = _fileName.Replace('/', '\\');
                 }
-                if (_fileName.EndsWith("\\"))
+                if (_fileName.EndsWith('\\'))
                 {
                     throw new InvalidOperationException("Illegal filename");
                 }
 
-                if (_fileName.Contains("\\"))
+                if (_fileName.Contains('\\'))
                 {
                     // trim any leading path
-                    int length = _fileName.Length;
-                    int num = length;
-                    while (--num >= 0)
-                    {
-                        char c = _fileName[num];
-                        if (c == '\\')
-                        {
-                            _fileName = _fileName.Substring(num + 1, length - num - 1);
-                        }
-                    }
+                    _fileName = Path.GetFileName(_fileName);
                 }
             }
         }
@@ -407,8 +412,8 @@ namespace SharpCompress.Compressors.Deflate
             byte[]? filenameBytes = (FileName is null) ? null
                 : _encoding.GetBytes(FileName);
 
-            int cbLength = (commentBytes is null) ? 0 : commentBytes.Length + 1;
-            int fnLength = (filenameBytes is null) ? 0 : filenameBytes.Length + 1;
+            int cbLength = commentBytes?.Length + 1 ?? 0;
+            int fnLength = filenameBytes?.Length + 1 ?? 0;
 
             int bufferLength = 10 + cbLength + fnLength;
             var header = new byte[bufferLength];
@@ -434,7 +439,7 @@ namespace SharpCompress.Compressors.Deflate
             header[i++] = flag;
 
             // mtime
-            if (!LastModified.HasValue)
+            if (LastModified is null)
             {
                 LastModified = DateTime.Now;
             }
@@ -456,7 +461,7 @@ namespace SharpCompress.Compressors.Deflate
             // filename
             if (fnLength != 0)
             {
-                Array.Copy(filenameBytes, 0, header, i, fnLength - 1);
+                Array.Copy(filenameBytes!, 0, header, i, fnLength - 1);
                 i += fnLength - 1;
                 header[i++] = 0; // terminate
             }
@@ -464,7 +469,7 @@ namespace SharpCompress.Compressors.Deflate
             // comment
             if (cbLength != 0)
             {
-                Array.Copy(commentBytes, 0, header, i, cbLength - 1);
+                Array.Copy(commentBytes!, 0, header, i, cbLength - 1);
                 i += cbLength - 1;
                 header[i++] = 0; // terminate
             }

src/SharpCompress/Compressors/Deflate/Inflate.cs

@@ -65,6 +65,8 @@
 
 using System;
 
+using SharpCompress.Algorithms;
+
 namespace SharpCompress.Compressors.Deflate
 {
     internal sealed class InflateBlocks
@@ -72,7 +74,7 @@ namespace SharpCompress.Compressors.Deflate
         private const int MANY = 1440;
 
         // Table for deflate from PKZIP's appnote.txt.
-        internal static readonly int[] border = {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
+        internal static readonly int[] border = { 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 };
 
         internal ZlibCodec _codec; // pointer back to this zlib stream
         internal int[] bb = new int[1]; // bit length tree depth
@@ -118,7 +120,7 @@ namespace SharpCompress.Compressors.Deflate
 
             if (checkfn != null)
             {
-                _codec._Adler32 = check = Adler.Adler32(0, null, 0, 0);
+                _codec._adler32 = check = 1;
             }
             return oldCheck;
         }
@@ -559,35 +561,35 @@ namespace SharpCompress.Compressors.Deflate
                         }
 
                         tb[0] = -1;
-                    {
-                        var bl = new[] {9}; // must be <= 9 for lookahead assumptions
-                        var bd = new[] {6}; // must be <= 9 for lookahead assumptions
-                        var tl = new int[1];
-                        var td = new int[1];
-
-                        t = table;
-                        t = inftree.inflate_trees_dynamic(257 + (t & 0x1f), 1 + ((t >> 5) & 0x1f), blens, bl, bd, tl,
-                                                          td, hufts, _codec);
-
-                        if (t != ZlibConstants.Z_OK)
                         {
-                            if (t == ZlibConstants.Z_DATA_ERROR)
-                            {
-                                blens = null;
-                                mode = InflateBlockMode.BAD;
-                            }
-                            r = t;
+                            var bl = new[] { 9 }; // must be <= 9 for lookahead assumptions
+                            var bd = new[] { 6 }; // must be <= 9 for lookahead assumptions
+                            var tl = new int[1];
+                            var td = new int[1];
 
-                            bitb = b;
-                            bitk = k;
-                            _codec.AvailableBytesIn = n;
-                            _codec.TotalBytesIn += p - _codec.NextIn;
-                            _codec.NextIn = p;
-                            writeAt = q;
-                            return Flush(r);
+                            t = table;
+                            t = inftree.inflate_trees_dynamic(257 + (t & 0x1f), 1 + ((t >> 5) & 0x1f), blens, bl, bd, tl,
+                                                              td, hufts, _codec);
+
+                            if (t != ZlibConstants.Z_OK)
+                            {
+                                if (t == ZlibConstants.Z_DATA_ERROR)
+                                {
+                                    blens = null;
+                                    mode = InflateBlockMode.BAD;
+                                }
+                                r = t;
+
+                                bitb = b;
+                                bitk = k;
+                                _codec.AvailableBytesIn = n;
+                                _codec.TotalBytesIn += p - _codec.NextIn;
+                                _codec.NextIn = p;
+                                writeAt = q;
+                                return Flush(r);
+                            }
+                            codes.Init(bl[0], bd[0], hufts, tl[0], hufts, td[0]);
                         }
-                        codes.Init(bl[0], bd[0], hufts, tl[0], hufts, td[0]);
-                    }
                         mode = InflateBlockMode.CODES;
                         goto case InflateBlockMode.CODES;
 
@@ -739,7 +741,7 @@ namespace SharpCompress.Compressors.Deflate
                 // update check information
                 if (checkfn != null)
                 {
-                    _codec._Adler32 = check = Adler.Adler32(check, window, readAt, nBytes);
+                    _codec._adler32 = check = Adler32.Calculate(check, window.AsSpan(readAt, nBytes));
                 }
 
                 // copy as far as end of window
@@ -1565,7 +1567,7 @@ namespace SharpCompress.Compressors.Deflate
         private const int PRESET_DICT = 0x20;
 
         private const int Z_DEFLATED = 8;
-        private static readonly byte[] mark = {0, 0, 0xff, 0xff};
+        private static readonly byte[] mark = { 0, 0, 0xff, 0xff };
 
         internal ZlibCodec _codec; // pointer back to this zlib stream
         internal InflateBlocks blocks; // current inflate_blocks state
@@ -1764,7 +1766,7 @@ namespace SharpCompress.Compressors.Deflate
                         _codec.AvailableBytesIn--;
                         _codec.TotalBytesIn++;
                         expectedCheck += (uint)(_codec.InputBuffer[_codec.NextIn++] & 0x000000ff);
-                        _codec._Adler32 = expectedCheck;
+                        _codec._adler32 = expectedCheck;
                         mode = InflateManagerMode.DICT0;
                         return ZlibConstants.Z_NEED_DICT;
 
@@ -1879,12 +1881,12 @@ namespace SharpCompress.Compressors.Deflate
                 throw new ZlibException("Stream error.");
             }
 
-            if (Adler.Adler32(1, dictionary, 0, dictionary.Length) != _codec._Adler32)
+            if (Adler32.Calculate(1, dictionary) != _codec._adler32)
             {
                 return ZlibConstants.Z_DATA_ERROR;
             }
 
-            _codec._Adler32 = Adler.Adler32(0, null, 0, 0);
+            _codec._adler32 = 1;
 
             if (length >= (1 << wbits))
             {

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 = 0,
+        Level0 = None,
 
         /// <summary>
         /// The fastest but least effective compression.
@@ -92,7 +92,7 @@ namespace SharpCompress.Compressors.Deflate
         /// <summary>
         /// A synonym for BestSpeed.
         /// </summary>
-        Level1 = 1,
+        Level1 = BestSpeed,
 
         /// <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 = 6,
+        Level6 = Default,
 
         /// <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 = 9
+        Level9 = BestCompression
     }
 
     /// <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
@@ -374,7 +374,7 @@ namespace SharpCompress.Compressors.Deflate
         };
 
         // extra bits for each bit length code
-        internal static readonly int[] extra_blbits = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 3, 7};
+        internal static readonly int[] extra_blbits = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 3, 7 };
 
         internal static readonly StaticTree Literals;
         internal static readonly StaticTree Distances;
@@ -405,88 +405,4 @@ namespace SharpCompress.Compressors.Deflate
             BitLengths = new StaticTree(null, extra_blbits, 0, InternalConstants.BL_CODES, InternalConstants.MAX_BL_BITS);
         }
     }
-
-    /// <summary>
-    /// Computes an Adler-32 checksum. 
-    /// </summary>
-    /// <remarks>
-    /// The Adler checksum is similar to a CRC checksum, but faster to compute, though less
-    /// reliable.  It is used in producing RFC1950 compressed streams.  The Adler checksum
-    /// is a required part of the "ZLIB" standard.  Applications will almost never need to
-    /// use this class directly.
-    /// </remarks>
-    internal sealed class Adler
-    {
-        // largest prime smaller than 65536
-        private static readonly uint BASE = 65521U;
-
-        // NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
-        private static readonly int NMAX = 5552;
-
-        internal static uint Adler32(uint adler, byte[]? buf, int index, int len)
-        {
-            if (buf is null)
-            {
-                return 1;
-            }
-
-            uint s1 = adler & 0xffffU;
-            uint s2 = (adler >> 16) & 0xffffU;
-
-            while (len > 0)
-            {
-                int k = len < NMAX ? len : NMAX;
-                len -= k;
-                while (k >= 16)
-                {
-                    //s1 += (buf[index++] & 0xff); s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    s1 += buf[index++];
-                    s2 += s1;
-                    k -= 16;
-                }
-                if (k != 0)
-                {
-                    do
-                    {
-                        s1 += buf[index++];
-                        s2 += s1;
-                    }
-                    while (--k != 0);
-                }
-                s1 %= BASE;
-                s2 %= BASE;
-            }
-            return (s2 << 16) | s1;
-        }
-    }
-}
+}

src/SharpCompress/Compressors/Deflate/ZlibBaseStream.cs

@@ -228,12 +228,12 @@ namespace SharpCompress.Compressors.Deflate
                     if (_wantCompress)
                     {
                         // Emit the GZIP trailer: CRC32 and  size mod 2^32
-                        byte[] intBuf = new byte[4];
+                        Span<byte> intBuf = stackalloc byte[4];
                         BinaryPrimitives.WriteInt32LittleEndian(intBuf, crc.Crc32Result);
-                        _stream.Write(intBuf, 0, 4);
-                        int c2 = (Int32)(crc.TotalBytesRead & 0x00000000FFFFFFFF);
+                        _stream.Write(intBuf);
+                        int c2 = (int)(crc.TotalBytesRead & 0x00000000FFFFFFFF);
                         BinaryPrimitives.WriteInt32LittleEndian(intBuf, c2);
-                        _stream.Write(intBuf, 0, 4);
+                        _stream.Write(intBuf);
                     }
                     else
                     {
@@ -256,17 +256,15 @@ namespace SharpCompress.Compressors.Deflate
                         }
 
                         // Read and potentially verify the GZIP trailer: CRC32 and  size mod 2^32
-                        byte[] trailer = new byte[8];
+                        Span<byte> trailer = stackalloc byte[8];
 
                         // workitem 8679
                         if (_z.AvailableBytesIn != 8)
                         {
                             // Make sure we have read to the end of the stream
-                            Array.Copy(_z.InputBuffer, _z.NextIn, trailer, 0, _z.AvailableBytesIn);
+                            _z.InputBuffer.AsSpan(_z.NextIn, _z.AvailableBytesIn).CopyTo(trailer);
                             int bytesNeeded = 8 - _z.AvailableBytesIn;
-                            int bytesRead = _stream.Read(trailer,
-                                                         _z.AvailableBytesIn,
-                                                         bytesNeeded);
+                            int bytesRead = _stream.Read(trailer.Slice(_z.AvailableBytesIn, bytesNeeded));
                             if (bytesNeeded != bytesRead)
                             {
                                 throw new ZlibException(String.Format(
@@ -276,12 +274,12 @@ namespace SharpCompress.Compressors.Deflate
                         }
                         else
                         {
-                            Array.Copy(_z.InputBuffer, _z.NextIn, trailer, 0, trailer.Length);
+                            _z.InputBuffer.AsSpan(_z.NextIn, trailer.Length).CopyTo(trailer);
                         }
 
                         Int32 crc32_expected = BinaryPrimitives.ReadInt32LittleEndian(trailer);
                         Int32 crc32_actual = crc.Crc32Result;
-                        Int32 isize_expected = BinaryPrimitives.ReadInt32LittleEndian(trailer.AsSpan(4));
+                        Int32 isize_expected = BinaryPrimitives.ReadInt32LittleEndian(trailer.Slice(4));
                         Int32 isize_actual = (Int32)(_z.TotalBytesOut & 0x00000000FFFFFFFF);
 
                         if (crc32_actual != crc32_expected)
@@ -413,8 +411,8 @@ namespace SharpCompress.Compressors.Deflate
             int totalBytesRead = 0;
 
             // read the header on the first read
-            byte[] header = new byte[10];
-            int n = _stream.Read(header, 0, header.Length);
+            Span<byte> header = stackalloc byte[10];
+            int n = _stream.Read(header);
 
             // workitem 8501: handle edge case (decompress empty stream)
             if (n == 0)
@@ -432,16 +430,16 @@ namespace SharpCompress.Compressors.Deflate
                 throw new ZlibException("Bad GZIP header.");
             }
 
-            Int32 timet = BinaryPrimitives.ReadInt32LittleEndian(header.AsSpan(4));
+            int timet = BinaryPrimitives.ReadInt32LittleEndian(header.Slice(4));
             _GzipMtime = TarHeader.EPOCH.AddSeconds(timet);
             totalBytesRead += n;
             if ((header[3] & 0x04) == 0x04)
             {
                 // read and discard extra field
-                n = _stream.Read(header, 0, 2); // 2-byte length field
+                n = _stream.Read(header.Slice(0, 2)); // 2-byte length field
                 totalBytesRead += n;
 
-                Int16 extraLength = (Int16)(header[0] + header[1] * 256);
+                short extraLength = (short)(header[0] + header[1] * 256);
                 byte[] extra = new byte[extraLength];
                 n = _stream.Read(extra, 0, extra.Length);
                 if (n != extraLength)
@@ -504,13 +502,37 @@ namespace SharpCompress.Compressors.Deflate
                 throw new ZlibException("Cannot Read after Writing.");
             }
 
+            int rc = 0;
+
+            // set up the output of the deflate/inflate codec:
+            _z.OutputBuffer = buffer;
+            _z.NextOut = offset;
+            _z.AvailableBytesOut = count;
+
             if (count == 0)
             {
                 return 0;
             }
             if (nomoreinput && _wantCompress)
             {
-                return 0; // workitem 8557
+                // no more input data available; therefore we flush to
+                // try to complete the read
+                rc = _z.Deflate(FlushType.Finish);
+
+                if (rc != ZlibConstants.Z_OK && rc != ZlibConstants.Z_STREAM_END)
+                {
+                    throw new ZlibException(String.Format("Deflating:  rc={0}  msg={1}", rc, _z.Message));
+                }
+
+                rc = (count - _z.AvailableBytesOut);
+
+                // calculate CRC after reading
+                if (crc != null)
+                {
+                    crc.SlurpBlock(buffer, offset, rc);
+                }
+
+                return rc;
             }
             if (buffer is null)
             {
@@ -529,13 +551,6 @@ namespace SharpCompress.Compressors.Deflate
                 throw new ArgumentOutOfRangeException(nameof(count));
             }
 
-            int rc = 0;
-
-            // set up the output of the deflate/inflate codec:
-            _z.OutputBuffer = buffer;
-            _z.NextOut = offset;
-            _z.AvailableBytesOut = count;
-
             // This is necessary in case _workingBuffer has been resized. (new byte[])
             // (The first reference to _workingBuffer goes through the private accessor which
             // may initialize it.)

src/SharpCompress/Compressors/Deflate/ZlibCodec.cs

@@ -137,7 +137,7 @@ namespace SharpCompress.Compressors.Deflate
         internal DeflateManager dstate;
         internal InflateManager istate;
 
-        internal uint _Adler32;
+        internal uint _adler32;
 
         /// <summary>
         /// The compression level to use in this codec.  Useful only in compression mode.
@@ -173,7 +173,7 @@ namespace SharpCompress.Compressors.Deflate
         /// <summary>
         /// The Adler32 checksum on the data transferred through the codec so far. You probably don't need to look at this.
         /// </summary>
-        public int Adler32 => (int)_Adler32;
+        public int Adler32 => (int)_adler32;
 
         /// <summary>
         /// Create a ZlibCodec.
@@ -737,7 +737,7 @@ namespace SharpCompress.Compressors.Deflate
 
             if (dstate.WantRfc1950HeaderBytes)
             {
-                _Adler32 = Adler.Adler32(_Adler32, InputBuffer, NextIn, len);
+                _adler32 = Algorithms.Adler32.Calculate(_adler32, InputBuffer.AsSpan(NextIn, len));
             }
             Array.Copy(InputBuffer, NextIn, buf, start, len);
             NextIn += len;

src/SharpCompress/Compressors/Deflate/ZlibConstants.cs

@@ -111,7 +111,7 @@ namespace SharpCompress.Compressors.Deflate
         /// <summary>
         /// The size of the working buffer used in the ZlibCodec class. Defaults to 8192 bytes.
         /// </summary>
-#if NETCF        
+#if NETCF
         public const int WorkingBufferSizeDefault = 8192;
 #else
         public const int WorkingBufferSizeDefault = 16384;

src/SharpCompress/Compressors/Deflate64/FastEncoderStatus.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Diagnostics;
 
 namespace SharpCompress.Compressors.Deflate64
@@ -10,7 +11,7 @@ namespace SharpCompress.Compressors.Deflate64
     {
         // static information for encoding, DO NOT MODIFY
 
-        internal static readonly byte[] FAST_ENCODER_TREE_STRUCTURE_DATA =
+        internal static ReadOnlySpan<byte> FAST_ENCODER_TREE_STRUCTURE_DATA => new byte[]
         {
             0xec,0xbd,0x07,0x60,0x1c,0x49,0x96,0x25,0x26,0x2f,0x6d,0xca,
             0x7b,0x7f,0x4a,0xf5,0x4a,0xd7,0xe0,0x74,0xa1,0x08,0x80,0x60,
@@ -23,7 +24,7 @@ namespace SharpCompress.Compressors.Deflate64
             0x1f,0x3f
         };
 
-        internal static readonly byte[] B_FINAL_FAST_ENCODER_TREE_STRUCTURE_DATA =
+        internal static ReadOnlySpan<byte> B_FINAL_FAST_ENCODER_TREE_STRUCTURE_DATA => new byte[]
         {
             0xed,0xbd,0x07,0x60,0x1c,0x49,0x96,0x25,0x26,0x2f,0x6d,0xca,
             0x7b,0x7f,0x4a,0xf5,0x4a,0xd7,0xe0,0x74,0xa1,0x08,0x80,0x60,

src/SharpCompress/Compressors/Deflate64/HuffmanTree.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
 using System.Diagnostics;
 using System.IO;
 
@@ -118,14 +119,14 @@ namespace SharpCompress.Compressors.Deflate64
         // This algorithm is described in standard RFC 1951
         private uint[] CalculateHuffmanCode()
         {
-            uint[] bitLengthCount = new uint[17];
+            Span<uint> bitLengthCount = stackalloc uint[17];
             foreach (int codeLength in _codeLengthArray)
             {
                 bitLengthCount[codeLength]++;
             }
             bitLengthCount[0] = 0;  // clear count for length 0
 
-            uint[] nextCode = new uint[17];
+            Span<uint> nextCode = stackalloc uint[17];
             uint tempCode = 0;
             for (int bits = 1; bits <= 16; bits++)
             {

src/SharpCompress/Compressors/Deflate64/InflaterManaged.cs

@@ -114,7 +114,7 @@ namespace SharpCompress.Compressors.Deflate64
         private void Reset()
         {
             _state = //_hasFormatReader ?
-                //InflaterState.ReadingHeader :   // start by reading Header info
+                     //InflaterState.ReadingHeader :   // start by reading Header info
                 InflaterState.ReadingBFinal;    // start by reading BFinal bit
         }
 
@@ -294,7 +294,7 @@ namespace SharpCompress.Compressors.Deflate64
                 //if (_hasFormatReader)
                 //    _state = InflaterState.StartReadingFooter;
                 //else
-                    _state = InflaterState.Done;
+                _state = InflaterState.Done;
             }
             return result;
         }

src/SharpCompress/Compressors/Deflate64/OutputWindow.cs

@@ -38,14 +38,14 @@ namespace SharpCompress.Compressors.Deflate64
         public void WriteLengthDistance(int length, int distance)
         {
             Debug.Assert((_bytesUsed + length) <= WINDOW_SIZE, "No Enough space");
-            
+
             // move backwards distance bytes in the output stream,
             // and copy length bytes from this position to the output stream.
             _bytesUsed += length;
             int copyStart = (_end - distance) & WINDOW_MASK; // start position for coping.
 
             int border = WINDOW_SIZE - length;
-            if (copyStart <= border && _end < border) 
+            if (copyStart <= border && _end < border)
             {
                 if (length <= distance)
                 {

src/SharpCompress/Compressors/Filters/BCJFilter.cs

@@ -4,9 +4,9 @@ namespace SharpCompress.Compressors.Filters
 {
     internal class BCJFilter : Filter
     {
-        private static readonly bool[] MASK_TO_ALLOWED_STATUS = {true, true, true, false, true, false, false, false};
+        private static readonly bool[] MASK_TO_ALLOWED_STATUS = { true, true, true, false, true, false, false, false };
 
-        private static readonly int[] MASK_TO_BIT_NUMBER = {0, 1, 2, 2, 3, 3, 3, 3};
+        private static readonly int[] MASK_TO_BIT_NUMBER = { 0, 1, 2, 2, 3, 3, 3, 3 };
 
         private int _pos;
         private int _prevMask;

src/SharpCompress/Compressors/Filters/BranchExecFilter.cs

@@ -0,0 +1,297 @@
+/*
+ * 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;
@@ -6,10 +6,8 @@ using SharpCompress.Compressors.LZMA.Utilites;
 
 namespace SharpCompress.Compressors.LZMA
 {
-    internal class AesDecoderStream : DecoderStream2
+    internal sealed class AesDecoderStream : DecoderStream2
     {
-        #region Variables
-
         private readonly Stream mStream;
         private readonly ICryptoTransform mDecoder;
         private readonly byte[] mBuffer;
@@ -20,26 +18,29 @@ namespace SharpCompress.Compressors.LZMA
         private int mUnderflow;
         private bool isDisposed;
 
-        #endregion
-
-        #region Stream Methods
-
         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;
 
-            if (((uint) input.Length & 15) != 0)
+            if (((uint)input.Length & 15) != 0)
             {
                 throw new NotSupportedException("AES decoder does not support padding.");
             }
 
-            int numCyclesPower;
-            byte[] salt, seed;
-            Init(info, out numCyclesPower, out salt, out seed);
+            Init(info, out int numCyclesPower, out byte[] salt, out byte[] seed);
 
             byte[] password = Encoding.Unicode.GetBytes(pass.CryptoGetTextPassword());
-            byte[] key = InitKey(numCyclesPower, salt, password);
+            byte[]? key = InitKey(numCyclesPower, salt, password);
+            if (key == null)
+            {
+                throw new InvalidOperationException("Initialized with null key");
+            }
 
             using (var aes = Aes.Create())
             {
@@ -72,21 +73,9 @@ namespace SharpCompress.Compressors.LZMA
             }
         }
 
-        public override long Position
-        {
-            get
-            {
-                return mWritten;
-            }
-        }
+        public override long Position => mWritten;
 
-        public override long Length
-        {
-            get
-            {
-                return mLimit;
-            }
-        }
+        public override long Length => mLimit;
 
         public override int Read(byte[] buffer, int offset, int count)
         {
@@ -127,7 +116,7 @@ namespace SharpCompress.Compressors.LZMA
             // the stream length is not a multiple of the block size.
             if (count > mLimit - mWritten)
             {
-                count = (int) (mLimit - mWritten);
+                count = (int)(mLimit - mWritten);
             }
 
             // We cannot transform less than 16 bytes into the target buffer,
@@ -150,8 +139,6 @@ namespace SharpCompress.Compressors.LZMA
             return processed;
         }
 
-        #endregion
-
         #region Private Methods
 
         private void Init(byte[] info, out int numCyclesPower, out byte[] salt, out byte[] iv)
@@ -161,8 +148,8 @@ namespace SharpCompress.Compressors.LZMA
 
             if ((bt & 0xC0) == 0)
             {
-                salt = new byte[0];
-                iv = new byte[0];
+                salt = Array.Empty<byte>();
+                iv = Array.Empty<byte>();
                 return;
             }
 
@@ -199,7 +186,7 @@ namespace SharpCompress.Compressors.LZMA
             }
         }
 
-        private byte[] InitKey(int mNumCyclesPower, byte[] salt, byte[] pass)
+        private byte[]? InitKey(int mNumCyclesPower, byte[] salt, byte[] pass)
         {
             if (mNumCyclesPower == 0x3F)
             {
@@ -220,54 +207,50 @@ namespace SharpCompress.Compressors.LZMA
             }
             else
             {
-#if NETSTANDARD1_3 || NETSTANDARD2_0
-                using (IncrementalHash sha = IncrementalHash.CreateHash(HashAlgorithmName.SHA256))
+#if NETSTANDARD2_0
+                using IncrementalHash sha = IncrementalHash.CreateHash(HashAlgorithmName.SHA256);
+                byte[] counter = new byte[8];
+                long numRounds = 1L << mNumCyclesPower;
+                for (long round = 0; round < numRounds; round++)
                 {
-                    byte[] counter = new byte[8];
-                    long numRounds = 1L << mNumCyclesPower;
-                    for (long round = 0; round < numRounds; round++)
-                    {
-                        sha.AppendData(salt, 0, salt.Length);
-                        sha.AppendData(pass, 0, pass.Length);
-                        sha.AppendData(counter, 0, 8);
+                    sha.AppendData(salt, 0, salt.Length);
+                    sha.AppendData(pass, 0, pass.Length);
+                    sha.AppendData(counter, 0, 8);
 
-                        // This mirrors the counter so we don't have to convert long to byte[] each round.
-                        // (It also ensures the counter is little endian, which BitConverter does not.)
-                        for (int i = 0; i < 8; i++)
+                    // This mirrors the counter so we don't have to convert long to byte[] each round.
+                    // (It also ensures the counter is little endian, which BitConverter does not.)
+                    for (int i = 0; i < 8; i++)
+                    {
+                        if (++counter[i] != 0)
                         {
-                            if (++counter[i] != 0)
-                            {
-                                break;
-                            }
+                            break;
                         }
                     }
-                    return sha.GetHashAndReset();
                 }
+                return sha.GetHashAndReset();
 #else
-                using (var sha = SHA256.Create())
+                using var sha = SHA256.Create();
+                byte[] counter = new byte[8];
+                long numRounds = 1L << mNumCyclesPower;
+                for (long round = 0; round < numRounds; round++)
                 {
-                    byte[] counter = new byte[8];
-                    long numRounds = 1L << mNumCyclesPower;
-                    for (long round = 0; round < numRounds; round++)
-                    {
-                        sha.TransformBlock(salt, 0, salt.Length, null, 0);
-                        sha.TransformBlock(pass, 0, pass.Length, null, 0);
-                        sha.TransformBlock(counter, 0, 8, null, 0);
+                    sha.TransformBlock(salt, 0, salt.Length, null, 0);
+                    sha.TransformBlock(pass, 0, pass.Length, null, 0);
+                    sha.TransformBlock(counter, 0, 8, null, 0);
 
-                        // This mirrors the counter so we don't have to convert long to byte[] each round.
-                        // (It also ensures the counter is little endian, which BitConverter does not.)
-                        for (int i = 0; i < 8; i++)
+                    // This mirrors the counter so we don't have to convert long to byte[] each round.
+                    // (It also ensures the counter is little endian, which BitConverter does not.)
+                    for (int i = 0; i < 8; i++)
+                    {
+                        if (++counter[i] != 0)
                         {
-                            if (++counter[i] != 0)
-                            {
-                                break;
-                            }
+                            break;
                         }
                     }
-
-                    sha.TransformFinalBlock(counter, 0, 0);
-                    return sha.Hash;
                 }
+
+                sha.TransformFinalBlock(counter, 0, 0);
+                return sha.Hash;
 #endif
             }
         }

src/SharpCompress/Compressors/LZMA/Bcj2DecoderStream.cs

@@ -215,7 +215,7 @@ namespace SharpCompress.Compressors.LZMA
 
             byte prevByte = 0;
             uint processedBytes = 0;
-            for (;;)
+            for (; ; )
             {
                 byte b = 0;
                 uint i;

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

src/SharpCompress/Compressors/LZMA/LZipStream.cs

@@ -14,7 +14,7 @@ namespace SharpCompress.Compressors.LZMA
     /// <summary>
     /// Stream supporting the LZIP format, as documented at http://www.nongnu.org/lzip/manual/lzip_manual.html
     /// </summary>
-    public class LZipStream : Stream
+    public sealed class LZipStream : Stream
     {
         private readonly Stream _stream;
         private readonly CountingWritableSubStream? _countingWritableSubStream;
@@ -59,16 +59,16 @@ namespace SharpCompress.Compressors.LZMA
                     crc32Stream.Dispose();
                     var compressedCount = _countingWritableSubStream!.Count;
 
-                    byte[] intBuf = new byte[8];
+                    Span<byte> intBuf = stackalloc byte[8];
                     BinaryPrimitives.WriteUInt32LittleEndian(intBuf, crc32Stream.Crc);
-                    _countingWritableSubStream.Write(intBuf, 0, 4);
+                    _countingWritableSubStream.Write(intBuf.Slice(0, 4));
 
                     BinaryPrimitives.WriteInt64LittleEndian(intBuf, _writeCount);
-                    _countingWritableSubStream.Write(intBuf, 0, 8);
+                    _countingWritableSubStream.Write(intBuf);
 
                     //total with headers
                     BinaryPrimitives.WriteUInt64LittleEndian(intBuf, compressedCount + 6 + 20);
-                    _countingWritableSubStream.Write(intBuf, 0, 8);
+                    _countingWritableSubStream.Write(intBuf);
                 }
                 _finished = true;
             }
@@ -117,6 +117,23 @@ namespace SharpCompress.Compressors.LZMA
 
         public override void SetLength(long value) => throw new NotImplementedException();
 
+
+#if !NETFRAMEWORK && !NETSTANDARD2_0
+
+        public override int Read(Span<byte> buffer)
+        {
+            return _stream.Read(buffer);
+        }
+
+        public override void Write(ReadOnlySpan<byte> buffer)
+        {
+            _stream.Write(buffer);
+
+            _writeCount += buffer.Length;
+        }
+
+#endif
+
         public override void Write(byte[] buffer, int offset, int count)
         {
             _stream.Write(buffer, offset, count);
@@ -151,9 +168,10 @@ namespace SharpCompress.Compressors.LZMA
             {
                 throw new ArgumentNullException(nameof(stream));
             }
+
             // Read the header
-            byte[] header = new byte[6];
-            int n = stream.Read(header, 0, header.Length);
+            Span<byte> header = stackalloc byte[6];
+            int n = stream.Read(header);
 
             // TODO: Handle reading only part of the header?
 

src/SharpCompress/Compressors/LZMA/LzmaEncoder.cs

@@ -766,7 +766,7 @@ namespace SharpCompress.Compressors.LZMA
                 {
                     offs += 2;
                 }
-                for (;; len++)
+                for (; ; len++)
                 {
                     UInt32 distance = _matchDistances[offs + 1];
                     UInt32 curAndLenPrice = normalMatchPrice + GetPosLenPrice(distance, len, posState);
@@ -1107,7 +1107,7 @@ namespace SharpCompress.Compressors.LZMA
                         offs += 2;
                     }
 
-                    for (UInt32 lenTest = startLen;; lenTest++)
+                    for (UInt32 lenTest = startLen; ; lenTest++)
                     {
                         UInt32 curBack = _matchDistances[offs + 1];
                         UInt32 curAndLenPrice = normalMatchPrice + GetPosLenPrice(curBack, lenTest, posState);
@@ -1649,7 +1649,7 @@ namespace SharpCompress.Compressors.LZMA
         {
             for (int m = 0; m < K_MATCH_FINDER_I_DS.Length; m++)
             {
-                if (s == K_MATCH_FINDER_I_DS[m])
+                if (string.Equals(s, K_MATCH_FINDER_I_DS[m], StringComparison.OrdinalIgnoreCase))
                 {
                     return m;
                 }
@@ -1665,129 +1665,129 @@ namespace SharpCompress.Compressors.LZMA
                 switch (propIDs[i])
                 {
                     case CoderPropId.NumFastBytes:
-                    {
-                        if (!(prop is Int32))
                         {
-                            throw new InvalidParamException();
-                        }
-                        Int32 numFastBytes = (Int32)prop;
-                        if (numFastBytes < 5 || numFastBytes > Base.K_MATCH_MAX_LEN)
-                        {
-                            throw new InvalidParamException();
-                        }
-                        _numFastBytes = (UInt32)numFastBytes;
-                        break;
-                    }
-                    case CoderPropId.Algorithm:
-                    {
-                        /*
-                        if (!(prop is Int32))
-                            throw new InvalidParamException();
-                        Int32 maximize = (Int32)prop;
-                        _fastMode = (maximize == 0);
-                        _maxMode = (maximize >= 2);
-                        */
-                        break;
-                    }
-                    case CoderPropId.MatchFinder:
-                    {
-                        if (!(prop is String))
-                        {
-                            throw new InvalidParamException();
-                        }
-                        EMatchFinderType matchFinderIndexPrev = _matchFinderType;
-                        int m = FindMatchFinder(((string)prop).ToUpper());
-                        if (m < 0)
-                        {
-                            throw new InvalidParamException();
-                        }
-                        _matchFinderType = (EMatchFinderType)m;
-                        if (_matchFinder != null && matchFinderIndexPrev != _matchFinderType)
-                        {
-                            _dictionarySizePrev = 0xFFFFFFFF;
-                            _matchFinder = null;
-                        }
-                        break;
-                    }
-                    case CoderPropId.DictionarySize:
-                    {
-                        const int kDicLogSizeMaxCompress = 30;
-                        if (!(prop is Int32))
-                        {
-                            throw new InvalidParamException();
-                        }
-                        ;
-                        Int32 dictionarySize = (Int32)prop;
-                        if (dictionarySize < (UInt32)(1 << Base.K_DIC_LOG_SIZE_MIN) ||
-                            dictionarySize > (UInt32)(1 << kDicLogSizeMaxCompress))
-                        {
-                            throw new InvalidParamException();
-                        }
-                        _dictionarySize = (UInt32)dictionarySize;
-                        int dicLogSize;
-                        for (dicLogSize = 0; dicLogSize < (UInt32)kDicLogSizeMaxCompress; dicLogSize++)
-                        {
-                            if (dictionarySize <= ((UInt32)(1) << dicLogSize))
+                            if (!(prop is Int32))
                             {
-                                break;
+                                throw new InvalidParamException();
                             }
+                            Int32 numFastBytes = (Int32)prop;
+                            if (numFastBytes < 5 || numFastBytes > Base.K_MATCH_MAX_LEN)
+                            {
+                                throw new InvalidParamException();
+                            }
+                            _numFastBytes = (UInt32)numFastBytes;
+                            break;
                         }
-                        _distTableSize = (UInt32)dicLogSize * 2;
-                        break;
-                    }
-                    case CoderPropId.PosStateBits:
-                    {
-                        if (!(prop is Int32))
+                    case CoderPropId.Algorithm:
                         {
-                            throw new InvalidParamException();
+                            /*
+                            if (!(prop is Int32))
+                                throw new InvalidParamException();
+                            Int32 maximize = (Int32)prop;
+                            _fastMode = (maximize == 0);
+                            _maxMode = (maximize >= 2);
+                            */
+                            break;
                         }
-                        Int32 v = (Int32)prop;
-                        if (v < 0 || v > (UInt32)Base.K_NUM_POS_STATES_BITS_ENCODING_MAX)
+                    case CoderPropId.MatchFinder:
                         {
-                            throw new InvalidParamException();
+                            if (!(prop is String))
+                            {
+                                throw new InvalidParamException();
+                            }
+                            EMatchFinderType matchFinderIndexPrev = _matchFinderType;
+                            int m = FindMatchFinder(((string)prop));
+                            if (m < 0)
+                            {
+                                throw new InvalidParamException();
+                            }
+                            _matchFinderType = (EMatchFinderType)m;
+                            if (_matchFinder != null && matchFinderIndexPrev != _matchFinderType)
+                            {
+                                _dictionarySizePrev = 0xFFFFFFFF;
+                                _matchFinder = null;
+                            }
+                            break;
                         }
-                        _posStateBits = v;
-                        _posStateMask = (((UInt32)1) << _posStateBits) - 1;
-                        break;
-                    }
-                    case CoderPropId.LitPosBits:
-                    {
-                        if (!(prop is Int32))
+                    case CoderPropId.DictionarySize:
                         {
-                            throw new InvalidParamException();
-                        }
-                        Int32 v = (Int32)prop;
-                        if (v < 0 || v > Base.K_NUM_LIT_POS_STATES_BITS_ENCODING_MAX)
-                        {
-                            throw new InvalidParamException();
-                        }
-                        _numLiteralPosStateBits = v;
-                        break;
-                    }
-                    case CoderPropId.LitContextBits:
-                    {
-                        if (!(prop is Int32))
-                        {
-                            throw new InvalidParamException();
-                        }
-                        Int32 v = (Int32)prop;
-                        if (v < 0 || v > Base.K_NUM_LIT_CONTEXT_BITS_MAX)
-                        {
-                            throw new InvalidParamException();
-                        }
+                            const int kDicLogSizeMaxCompress = 30;
+                            if (!(prop is Int32))
+                            {
+                                throw new InvalidParamException();
+                            }
                         ;
-                        _numLiteralContextBits = v;
-                        break;
-                    }
-                    case CoderPropId.EndMarker:
-                    {
-                        if (!(prop is Boolean))
-                        {
-                            throw new InvalidParamException();
+                            Int32 dictionarySize = (Int32)prop;
+                            if (dictionarySize < (UInt32)(1 << Base.K_DIC_LOG_SIZE_MIN) ||
+                                dictionarySize > (UInt32)(1 << kDicLogSizeMaxCompress))
+                            {
+                                throw new InvalidParamException();
+                            }
+                            _dictionarySize = (UInt32)dictionarySize;
+                            int dicLogSize;
+                            for (dicLogSize = 0; dicLogSize < (UInt32)kDicLogSizeMaxCompress; dicLogSize++)
+                            {
+                                if (dictionarySize <= ((UInt32)(1) << dicLogSize))
+                                {
+                                    break;
+                                }
+                            }
+                            _distTableSize = (UInt32)dicLogSize * 2;
+                            break;
+                        }
+                    case CoderPropId.PosStateBits:
+                        {
+                            if (!(prop is Int32))
+                            {
+                                throw new InvalidParamException();
+                            }
+                            Int32 v = (Int32)prop;
+                            if (v < 0 || v > (UInt32)Base.K_NUM_POS_STATES_BITS_ENCODING_MAX)
+                            {
+                                throw new InvalidParamException();
+                            }
+                            _posStateBits = v;
+                            _posStateMask = (((UInt32)1) << _posStateBits) - 1;
+                            break;
+                        }
+                    case CoderPropId.LitPosBits:
+                        {
+                            if (!(prop is Int32))
+                            {
+                                throw new InvalidParamException();
+                            }
+                            Int32 v = (Int32)prop;
+                            if (v < 0 || v > Base.K_NUM_LIT_POS_STATES_BITS_ENCODING_MAX)
+                            {
+                                throw new InvalidParamException();
+                            }
+                            _numLiteralPosStateBits = v;
+                            break;
+                        }
+                    case CoderPropId.LitContextBits:
+                        {
+                            if (!(prop is Int32))
+                            {
+                                throw new InvalidParamException();
+                            }
+                            Int32 v = (Int32)prop;
+                            if (v < 0 || v > Base.K_NUM_LIT_CONTEXT_BITS_MAX)
+                            {
+                                throw new InvalidParamException();
+                            }
+                        ;
+                            _numLiteralContextBits = v;
+                            break;
+                        }
+                    case CoderPropId.EndMarker:
+                        {
+                            if (!(prop is Boolean))
+                            {
+                                throw new InvalidParamException();
+                            }
+                            SetWriteEndMarkerMode((Boolean)prop);
+                            break;
                         }
-                        SetWriteEndMarkerMode((Boolean)prop);
-                        break;
-                    }
                     default:
                         throw new InvalidParamException();
                 }

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

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Diagnostics;
 using System.IO;
 
@@ -21,16 +21,17 @@ namespace SharpCompress.Compressors.LZMA.Utilites
 
         protected override void Dispose(bool disposing)
         {
-            if (_mCurrentCrc != _mExpectedCrc)
-            {
-                throw new InvalidOperationException();
-            }
+            //Nanook - is not equal here - _mCurrentCrc is yet to be negated
+            //if (_mCurrentCrc != _mExpectedCrc)
+            //{
+            //    throw new InvalidOperationException();
+            //}
             try
             {
                 if (disposing && !_mClosed)
                 {
                     _mClosed = true;
-                    _mCurrentCrc = Crc.Finish(_mCurrentCrc);
+                    _mCurrentCrc = Crc.Finish(_mCurrentCrc); //now becomes equal
 #if DEBUG
                     if (_mCurrentCrc == _mExpectedCrc)
                     {
@@ -54,6 +55,10 @@ namespace SharpCompress.Compressors.LZMA.Utilites
                     }
                     Debug.WriteLine("entropy: " + (int)(entropy * 100) + "%");
 #endif
+                    if (_mCurrentCrc != _mExpectedCrc) //moved test to here
+                    {
+                        throw new InvalidOperationException();
+                    }
                 }
             }
             finally
@@ -102,4 +107,4 @@ 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 Exception("Assertion failed.");
+                throw new InvalidOperationException("Assertion failed.");
             }
         }
 
@@ -89,4 +89,4 @@ namespace SharpCompress.Compressors.LZMA.Utilites
             }
         }
     }
-}
+}