Fix relavant package references

Expose Last Modified time on GZipStream.  Add CRC and Size to GZipEntries on Archive

.config/dotnet-tools.json

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

.github/workflows/dotnetcore.yml

@@ -1,5 +1,5 @@
 name: SharpCompress
-on: [push]
+on: [push, pull_request]
 
 jobs:
   build:
@@ -12,6 +12,13 @@ jobs:
     - uses: actions/checkout@v1
     - uses: actions/setup-dotnet@v1
       with:
-        dotnet-version: 3.1.100
-    - name: Run the Cake script
-      uses: ecampidoglio/cake-action@master
+        dotnet-version: 5.0.101
+    - run: dotnet run -p build/build.csproj
+    - uses: actions/upload-artifact@v2
+      with:
+        name: ${{ matrix.os }}-sharpcompress.nupkg
+        path: artifacts/*
+    - uses: actions/upload-artifact@v2
+      with:
+        name: ${{ matrix.os }}-sharpcompress.snupkg
+        path: artifacts/*

.gitignore

@@ -17,3 +17,4 @@ tools
 .idea/
 
 .DS_Store
+*.snupkg

README.md

@@ -1,12 +1,9 @@
 # SharpCompress
 
-SharpCompress is a compression library in pure C# for .NET Standard 1.3 and 2.0 that can unrar, un7zip, unzip, untar unbzip2 and ungzip with forward-only reading and file random access APIs. Write support for zip/tar/bzip2/gzip 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).
 
-AppVeyor Build -
-[![Build status](https://ci.appveyor.com/api/projects/status/voxg971oemmvxh1e/branch/master?svg=true)](https://ci.appveyor.com/project/adamhathcock/sharpcompress/branch/master)
-
 GitHub Actions Build -
 [![GitHubActions](https://github.com/adamhathcock/sharpcompress/workflows/SharpCompress/badge.svg)](https://circleci.com/gh/adamhathcock/sharpcompress)
 

SharpCompress.sln

@@ -13,6 +13,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "SharpCompress", "src\SharpC
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "SharpCompress.Test", "tests\SharpCompress.Test\SharpCompress.Test.csproj", "{F2B1A1EB-0FA6-40D0-8908-E13247C7226F}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "build", "build\build.csproj", "{D4D613CB-5E94-47FB-85BE-B8423D20C545}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -27,6 +29,10 @@ Global
 		{F2B1A1EB-0FA6-40D0-8908-E13247C7226F}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{F2B1A1EB-0FA6-40D0-8908-E13247C7226F}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{F2B1A1EB-0FA6-40D0-8908-E13247C7226F}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D4D613CB-5E94-47FB-85BE-B8423D20C545}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D4D613CB-5E94-47FB-85BE-B8423D20C545}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D4D613CB-5E94-47FB-85BE-B8423D20C545}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D4D613CB-5E94-47FB-85BE-B8423D20C545}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

SharpCompress.sln.DotSettings

@@ -126,4 +126,7 @@
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EAddAccessorOwnerDeclarationBracesMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002ECSharpPlaceAttributeOnSameLineMigration/@EntryIndexedValue">True</s:Boolean>
 	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateBlankLinesAroundFieldToBlankLinesAroundProperty/@EntryIndexedValue">True</s:Boolean>
-	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateThisQualifierSettings/@EntryIndexedValue">True</s:Boolean></wpf:ResourceDictionary>
+	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EMigrateThisQualifierSettings/@EntryIndexedValue">True</s:Boolean>
+	<s:String x:Key="/Default/Environment/UnitTesting/UnitTestSessionStore/Sessions/=6af8f80e_002D9fdd_002D4223_002D8e02_002D473db916f9b2/@EntryIndexedValue">&lt;SessionState ContinuousTestingIsOn="False" ContinuousTestingMode="0" FrameworkVersion="{x:Null}" IsLocked="False" Name="All tests from Solution" PlatformMonoPreference="{x:Null}" PlatformType="{x:Null}" xmlns="urn:schemas-jetbrains-com:jetbrains-ut-session" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
+  &lt;Solution /&gt;
+&lt;/SessionState&gt;</s:String></wpf:ResourceDictionary>

appveyor.yml

@@ -1,20 +0,0 @@
-version: '{build}'
-image: Visual Studio 2019
-
-pull_requests:
-  do_not_increment_build_number: true
-
-branches:
-  only:
-  - master
-
-nuget:
-  disable_publish_on_pr: true
-
-build_script:
-- ps: .\build.ps1
-
-test: off
-
-artifacts:
-- path: src\SharpCompress\bin\Release\*.nupkg

build.cake

@@ -1,89 +0,0 @@
-var target = Argument("target", "Default");
-var tag = Argument("tag", "cake");
-
-Task("Restore")
-  .Does(() =>
-{
-    DotNetCoreRestore(".");
-});
-
-Task("Build")
-  .IsDependentOn("Restore")
-  .Does(() =>
-{
-    if (IsRunningOnWindows())
-    {
-        MSBuild("./sharpcompress.sln", c => 
-        { 
-            c.SetConfiguration("Release")
-            .SetVerbosity(Verbosity.Minimal)
-            .UseToolVersion(MSBuildToolVersion.VS2019);
-        });
-    }
-    else 
-    {
-        var settings = new DotNetCoreBuildSettings
-        {
-            Framework = "netstandard1.3",
-            Configuration = "Release",
-            NoRestore = true
-        };
-
-        DotNetCoreBuild("./src/SharpCompress/SharpCompress.csproj", settings);
-
-        settings.Framework = "netstandard2.0";
-        DotNetCoreBuild("./src/SharpCompress/SharpCompress.csproj", settings);
-
-        settings.Framework = "netstandard2.1";
-        DotNetCoreBuild("./src/SharpCompress/SharpCompress.csproj", settings);
-    }
-});
-
-Task("Test")
-  .IsDependentOn("Build")
-  .Does(() =>
-{
-    var files = GetFiles("tests/**/*.csproj");
-    foreach(var file in files)
-    {
-        var settings = new DotNetCoreTestSettings
-        {
-            Configuration = "Release",
-            Framework = "netcoreapp3.1"
-        };
-        DotNetCoreTest(file.ToString(), settings);
-    }
-});
-
-Task("Pack")
-    .IsDependentOn("Build")
-    .Does(() => 
-{
-    if (IsRunningOnWindows())
-    {
-        MSBuild("src/SharpCompress/SharpCompress.csproj", c => c
-            .SetConfiguration("Release")
-            .SetVerbosity(Verbosity.Minimal)
-            .UseToolVersion(MSBuildToolVersion.VS2019)
-            .WithProperty("NoBuild", "true")
-            .WithTarget("Pack"));
-    } 
-    else 
-    {
-        Information("Skipping Pack as this is not Windows");
-    }
-});
-
-Task("Default")
-    .IsDependentOn("Restore")
-    .IsDependentOn("Build")
-    .IsDependentOn("Test")
-    .IsDependentOn("Pack");
-
- Task("RunTests")
-    .IsDependentOn("Restore")
-    .IsDependentOn("Build")
-    .IsDependentOn("Test");
-
-
-RunTarget(target);

build.ps1

@@ -1,228 +0,0 @@
-##########################################################################
-# This is the Cake bootstrapper script for PowerShell.
-# This file was downloaded from https://github.com/cake-build/resources
-# Feel free to change this file to fit your needs.
-##########################################################################
-
-<#
-
-.SYNOPSIS
-This is a Powershell script to bootstrap a Cake build.
-
-.DESCRIPTION
-This Powershell script will download NuGet if missing, restore NuGet tools (including Cake)
-and execute your Cake build script with the parameters you provide.
-
-.PARAMETER Script
-The build script to execute.
-.PARAMETER Target
-The build script target to run.
-.PARAMETER Configuration
-The build configuration to use.
-.PARAMETER Verbosity
-Specifies the amount of information to be displayed.
-.PARAMETER Experimental
-Tells Cake to use the latest Roslyn release.
-.PARAMETER WhatIf
-Performs a dry run of the build script.
-No tasks will be executed.
-.PARAMETER Mono
-Tells Cake to use the Mono scripting engine.
-.PARAMETER SkipToolPackageRestore
-Skips restoring of packages.
-.PARAMETER ScriptArgs
-Remaining arguments are added here.
-
-.LINK
-http://cakebuild.net
-
-#>
-
-[CmdletBinding()]
-Param(
-    [string]$Script = "build.cake",
-    [string]$Target = "Default",
-    [ValidateSet("Release", "Debug")]
-    [string]$Configuration = "Release",
-    [ValidateSet("Quiet", "Minimal", "Normal", "Verbose", "Diagnostic")]
-    [string]$Verbosity = "Verbose",
-    [switch]$Experimental,
-    [Alias("DryRun","Noop")]
-    [switch]$WhatIf,
-    [switch]$Mono,
-    [switch]$SkipToolPackageRestore,
-    [Parameter(Position=0,Mandatory=$false,ValueFromRemainingArguments=$true)]
-    [string[]]$ScriptArgs
-)
-
-[Reflection.Assembly]::LoadWithPartialName("System.Security") | Out-Null
-function MD5HashFile([string] $filePath)
-{
-    if ([string]::IsNullOrEmpty($filePath) -or !(Test-Path $filePath -PathType Leaf))
-    {
-        return $null
-    }
-
-    [System.IO.Stream] $file = $null;
-    [System.Security.Cryptography.MD5] $md5 = $null;
-    try
-    {
-        $md5 = [System.Security.Cryptography.MD5]::Create()
-        $file = [System.IO.File]::OpenRead($filePath)
-        return [System.BitConverter]::ToString($md5.ComputeHash($file))
-    }
-    finally
-    {
-        if ($file -ne $null)
-        {
-            $file.Dispose()
-        }
-    }
-}
-
-Write-Host "Preparing to run build script..."
-
-if(!$PSScriptRoot){
-    $PSScriptRoot = Split-Path $MyInvocation.MyCommand.Path -Parent
-}
-
-$TOOLS_DIR = Join-Path $PSScriptRoot "tools"
-$ADDINS_DIR = Join-Path $TOOLS_DIR "addins"
-$MODULES_DIR = Join-Path $TOOLS_DIR "modules"
-$NUGET_EXE = Join-Path $TOOLS_DIR "nuget.exe"
-$CAKE_EXE = Join-Path $TOOLS_DIR "Cake/Cake.exe"
-$NUGET_URL = "https://dist.nuget.org/win-x86-commandline/latest/nuget.exe"
-$PACKAGES_CONFIG = Join-Path $TOOLS_DIR "packages.config"
-$PACKAGES_CONFIG_MD5 = Join-Path $TOOLS_DIR "packages.config.md5sum"
-$ADDINS_PACKAGES_CONFIG = Join-Path $ADDINS_DIR "packages.config"
-$MODULES_PACKAGES_CONFIG = Join-Path $MODULES_DIR "packages.config"
-
-# Should we use mono?
-$UseMono = "";
-if($Mono.IsPresent) {
-    Write-Verbose -Message "Using the Mono based scripting engine."
-    $UseMono = "-mono"
-}
-
-# Should we use the new Roslyn?
-$UseExperimental = "";
-if($Experimental.IsPresent -and !($Mono.IsPresent)) {
-    Write-Verbose -Message "Using experimental version of Roslyn."
-    $UseExperimental = "-experimental"
-}
-
-# Is this a dry run?
-$UseDryRun = "";
-if($WhatIf.IsPresent) {
-    $UseDryRun = "-dryrun"
-}
-
-# Make sure tools folder exists
-if ((Test-Path $PSScriptRoot) -and !(Test-Path $TOOLS_DIR)) {
-    Write-Verbose -Message "Creating tools directory..."
-    New-Item -Path $TOOLS_DIR -Type directory | out-null
-}
-
-# Make sure that packages.config exist.
-if (!(Test-Path $PACKAGES_CONFIG)) {
-    Write-Verbose -Message "Downloading packages.config..."
-    try { (New-Object System.Net.WebClient).DownloadFile("http://cakebuild.net/download/bootstrapper/packages", $PACKAGES_CONFIG) } catch {
-        Throw "Could not download packages.config."
-    }
-}
-
-# Try find NuGet.exe in path if not exists
-if (!(Test-Path $NUGET_EXE)) {
-    Write-Verbose -Message "Trying to find nuget.exe in PATH..."
-    $existingPaths = $Env:Path -Split ';' | Where-Object { (![string]::IsNullOrEmpty($_)) -and (Test-Path $_ -PathType Container) }
-    $NUGET_EXE_IN_PATH = Get-ChildItem -Path $existingPaths -Filter "nuget.exe" | Select -First 1
-    if ($NUGET_EXE_IN_PATH -ne $null -and (Test-Path $NUGET_EXE_IN_PATH.FullName)) {
-        Write-Verbose -Message "Found in PATH at $($NUGET_EXE_IN_PATH.FullName)."
-        $NUGET_EXE = $NUGET_EXE_IN_PATH.FullName
-    }
-}
-
-# Try download NuGet.exe if not exists
-if (!(Test-Path $NUGET_EXE)) {
-    Write-Verbose -Message "Downloading NuGet.exe..."
-    try {
-        (New-Object System.Net.WebClient).DownloadFile($NUGET_URL, $NUGET_EXE)
-    } catch {
-        Throw "Could not download NuGet.exe."
-    }
-}
-
-# Save nuget.exe path to environment to be available to child processed
-$ENV:NUGET_EXE = $NUGET_EXE
-
-# Restore tools from NuGet?
-if(-Not $SkipToolPackageRestore.IsPresent) {
-    Push-Location
-    Set-Location $TOOLS_DIR
-
-    # Check for changes in packages.config and remove installed tools if true.
-    [string] $md5Hash = MD5HashFile($PACKAGES_CONFIG)
-    if((!(Test-Path $PACKAGES_CONFIG_MD5)) -Or
-      ($md5Hash -ne (Get-Content $PACKAGES_CONFIG_MD5 ))) {
-        Write-Verbose -Message "Missing or changed package.config hash..."
-        Remove-Item * -Recurse -Exclude packages.config,nuget.exe
-    }
-
-    Write-Verbose -Message "Restoring tools from NuGet..."
-    $NuGetOutput = Invoke-Expression "&`"$NUGET_EXE`" install -ExcludeVersion -OutputDirectory `"$TOOLS_DIR`""
-
-    if ($LASTEXITCODE -ne 0) {
-        Throw "An error occured while restoring NuGet tools."
-    }
-    else
-    {
-        $md5Hash | Out-File $PACKAGES_CONFIG_MD5 -Encoding "ASCII"
-    }
-    Write-Verbose -Message ($NuGetOutput | out-string)
-    
-    Pop-Location
-}
-
-# Restore addins from NuGet
-if (Test-Path $ADDINS_PACKAGES_CONFIG) {
-    Push-Location
-    Set-Location $ADDINS_DIR
-
-    Write-Verbose -Message "Restoring addins from NuGet..."
-    $NuGetOutput = Invoke-Expression "&`"$NUGET_EXE`" install -ExcludeVersion -OutputDirectory `"$ADDINS_DIR`""
-
-    if ($LASTEXITCODE -ne 0) {
-        Throw "An error occured while restoring NuGet addins."
-    }
-
-    Write-Verbose -Message ($NuGetOutput | out-string)
-
-    Pop-Location
-}
-
-# Restore modules from NuGet
-if (Test-Path $MODULES_PACKAGES_CONFIG) {
-    Push-Location
-    Set-Location $MODULES_DIR
-
-    Write-Verbose -Message "Restoring modules from NuGet..."
-    $NuGetOutput = Invoke-Expression "&`"$NUGET_EXE`" install -ExcludeVersion -OutputDirectory `"$MODULES_DIR`""
-
-    if ($LASTEXITCODE -ne 0) {
-        Throw "An error occured while restoring NuGet modules."
-    }
-
-    Write-Verbose -Message ($NuGetOutput | out-string)
-
-    Pop-Location
-}
-
-# Make sure that Cake has been installed.
-if (!(Test-Path $CAKE_EXE)) {
-    Throw "Could not find Cake.exe at $CAKE_EXE"
-}
-
-# Start Cake
-Write-Host "Running build script..."
-Invoke-Expression "& `"$CAKE_EXE`" `"$Script`" -target=`"$Target`" -configuration=`"$Configuration`" -verbosity=`"$Verbosity`" $UseMono $UseDryRun $UseExperimental $ScriptArgs"
-exit $LASTEXITCODE

build.sh

@@ -1,42 +0,0 @@
-#!/usr/bin/env bash
-##########################################################################
-# This is the Cake bootstrapper script for Linux and OS X.
-# This file was downloaded from https://github.com/cake-build/resources
-# Feel free to change this file to fit your needs.
-##########################################################################
-
-# Define directories.
-SCRIPT_DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
-TOOLS_DIR=$SCRIPT_DIR/tools
-CAKE_VERSION=0.27.1
-CAKE_DLL=$TOOLS_DIR/Cake.CoreCLR.$CAKE_VERSION/Cake.dll
-
-# Make sure the tools folder exist.
-if [ ! -d "$TOOLS_DIR" ]; then
-  mkdir "$TOOLS_DIR"
-fi
-
-###########################################################################
-# INSTALL CAKE
-###########################################################################
-
-if [ ! -f "$CAKE_DLL" ]; then
-    curl -Lsfo Cake.CoreCLR.zip "https://www.nuget.org/api/v2/package/Cake.CoreCLR/$CAKE_VERSION" && unzip -q Cake.CoreCLR.zip -d "$TOOLS_DIR/Cake.CoreCLR.$CAKE_VERSION" && rm -f Cake.CoreCLR.zip
-    if [ $? -ne 0 ]; then
-        echo "An error occured while installing Cake."
-        exit 1
-    fi
-fi
-
-# Make sure that Cake has been installed.
-if [ ! -f "$CAKE_DLL" ]; then
-    echo "Could not find Cake.exe at '$CAKE_DLL'."
-    exit 1
-fi
-
-###########################################################################
-# RUN BUILD SCRIPT
-###########################################################################
-
-# Start Cake
-exec dotnet "$CAKE_DLL" "$@"

build/Program.cs

@@ -0,0 +1,83 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.InteropServices;
+using GlobExpressions;
+using static Bullseye.Targets;
+using static SimpleExec.Command;
+
+class Program
+{
+    private const string Clean = "clean";
+    private const string Format = "format";
+    private const string Build = "build";
+    private const string Test = "test";
+    private const string Publish = "publish";
+
+    static void Main(string[] args)
+    {
+        Target(Clean,
+            ForEach("**/bin", "**/obj"),
+            dir =>
+            {
+                IEnumerable<string> GetDirectories(string d)
+                {
+                    return Glob.Directories(".", d);
+                }
+
+                void RemoveDirectory(string d)
+                {
+                    if (Directory.Exists(d))
+                    {
+                        Console.WriteLine(d);
+                        Directory.Delete(d, true);
+                    }
+                }
+
+                foreach (var d in GetDirectories(dir))
+                {
+                    RemoveDirectory(d);
+                }
+            });
+
+        Target(Format, () =>
+        {
+            Run("dotnet", "tool restore");
+            Run("dotnet", "format --check");
+        });
+
+        Target(Build, DependsOn(Format),
+               framework =>
+               {
+                   if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && framework == "net46")
+                   {
+                       return;
+                   }
+                   Run("dotnet", "build src/SharpCompress/SharpCompress.csproj -c Release");
+               });
+
+        Target(Test, DependsOn(Build), ForEach("net5.0"),
+               framework =>
+               {
+                   IEnumerable<string> GetFiles(string d)
+                   {
+                       return Glob.Files(".", 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("default", DependsOn(Publish), () => Console.WriteLine("Done!"));
+
+        RunTargetsAndExit(args);
+    }
+}

build/build.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Bullseye" Version="3.6.0" />
+    <PackageReference Include="Glob" Version="1.1.8" />
+    <PackageReference Include="SimpleExec" Version="6.4.0" />
+  </ItemGroup>
+
+</Project>

global.json

@@ -0,0 +1,5 @@
+{
+  "sdk": {
+    "version": "5.0.101"
+  }
+}

src/SharpCompress/Algorithms/Alder32.cs

@@ -0,0 +1,285 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the GNU Affero General Public License, Version 3.
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+#if !NETSTANDARD2_0 && !NETSTANDARD2_1
+using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.X86;
+#endif
+
+namespace SharpCompress.Algorithms
+{
+    /// <summary>
+    /// Calculates the 32 bit Adler checksum of a given buffer according to
+    /// RFC 1950. ZLIB Compressed Data Format Specification version 3.3)
+    /// </summary>
+    internal static class Adler32
+    {
+        /// <summary>
+        /// The default initial seed value of a Adler32 checksum calculation.
+        /// </summary>
+        public const uint SeedValue = 1U;
+
+#if !NETSTANDARD2_0 && !NETSTANDARD2_1
+        private const int MinBufferSize = 64;
+#endif
+
+        // Largest prime smaller than 65536
+        private const uint BASE = 65521;
+
+        // NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
+        private const uint NMAX = 5552;
+
+        /// <summary>
+        /// Calculates the Adler32 checksum with the bytes taken from the span.
+        /// </summary>
+        /// <param name="buffer">The readonly span of bytes.</param>
+        /// <returns>The <see cref="uint"/>.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static uint Calculate(ReadOnlySpan<byte> buffer)
+        {
+            return Calculate(SeedValue, buffer);
+        }
+
+        /// <summary>
+        /// Calculates the Adler32 checksum with the bytes taken from the span and seed.
+        /// </summary>
+        /// <param name="adler">The input Adler32 value.</param>
+        /// <param name="buffer">The readonly span of bytes.</param>
+        /// <returns>The <see cref="uint"/>.</returns>
+        public static uint Calculate(uint adler, ReadOnlySpan<byte> buffer)
+        {
+            if (buffer.IsEmpty)
+            {
+                return SeedValue;
+            }
+
+#if !NETSTANDARD2_0 && !NETSTANDARD2_1
+            if (Sse3.IsSupported && buffer.Length >= MinBufferSize)
+            {
+                return CalculateSse(adler, buffer);
+            }
+
+            return CalculateScalar(adler, buffer);
+#else
+            return CalculateScalar(adler, buffer);
+#endif
+        }
+
+        // Based on https://github.com/chromium/chromium/blob/master/third_party/zlib/adler32_simd.c
+#if !NETSTANDARD2_0 && !NETSTANDARD2_1
+        private static unsafe uint CalculateSse(uint adler, ReadOnlySpan<byte> buffer)
+        {
+            uint s1 = adler & 0xFFFF;
+            uint s2 = (adler >> 16) & 0xFFFF;
+
+            // Process the data in blocks.
+            const int BLOCK_SIZE = 1 << 5;
+
+            uint length = (uint)buffer.Length;
+            uint blocks = length / BLOCK_SIZE;
+            length -= blocks * BLOCK_SIZE;
+
+            int index = 0;
+            fixed (byte* bufferPtr = &buffer[0])
+            {
+                index += (int)blocks * BLOCK_SIZE;
+                var localBufferPtr = bufferPtr;
+
+                // _mm_setr_epi8 on x86
+                var tap1 = Vector128.Create(32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17);
+                var tap2 = Vector128.Create(16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1);
+                Vector128<byte> zero = Vector128<byte>.Zero;
+                var ones = Vector128.Create((short)1);
+
+                while (blocks > 0)
+                {
+                    uint n = NMAX / BLOCK_SIZE;  /* The NMAX constraint. */
+                    if (n > blocks)
+                    {
+                        n = blocks;
+                    }
+
+                    blocks -= n;
+
+                    // Process n blocks of data. At most NMAX data bytes can be
+                    // processed before s2 must be reduced modulo BASE.
+                    Vector128<int> v_ps = Vector128.CreateScalar(s1 * n).AsInt32();
+                    Vector128<int> v_s2 = Vector128.CreateScalar(s2).AsInt32();
+                    Vector128<int> v_s1 = Vector128<int>.Zero;
+
+                    do
+                    {
+                        // Load 32 input bytes.
+                        Vector128<byte> bytes1 = Sse3.LoadDquVector128(localBufferPtr);
+                        Vector128<byte> bytes2 = Sse3.LoadDquVector128(localBufferPtr + 16);
+
+                        // Add previous block byte sum to v_ps.
+                        v_ps = Sse2.Add(v_ps, v_s1);
+
+                        // Horizontally add the bytes for s1, multiply-adds the
+                        // bytes by [ 32, 31, 30, ... ] for s2.
+                        v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes1, zero).AsInt32());
+                        Vector128<short> mad1 = Ssse3.MultiplyAddAdjacent(bytes1, tap1);
+                        v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad1, ones));
+
+                        v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes2, zero).AsInt32());
+                        Vector128<short> mad2 = Ssse3.MultiplyAddAdjacent(bytes2, tap2);
+                        v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad2, ones));
+
+                        localBufferPtr += BLOCK_SIZE;
+                    }
+                    while (--n > 0);
+
+                    v_s2 = Sse2.Add(v_s2, Sse2.ShiftLeftLogical(v_ps, 5));
+
+                    // Sum epi32 ints v_s1(s2) and accumulate in s1(s2).
+                    const byte S2301 = 0b1011_0001;  // A B C D -> B A D C
+                    const byte S1032 = 0b0100_1110;  // A B C D -> C D A B
+
+                    v_s1 = Sse2.Add(v_s1, Sse2.Shuffle(v_s1, S2301));
+                    v_s1 = Sse2.Add(v_s1, Sse2.Shuffle(v_s1, S1032));
+
+                    s1 += (uint)v_s1.ToScalar();
+
+                    v_s2 = Sse2.Add(v_s2, Sse2.Shuffle(v_s2, S2301));
+                    v_s2 = Sse2.Add(v_s2, Sse2.Shuffle(v_s2, S1032));
+
+                    s2 = (uint)v_s2.ToScalar();
+
+                    // Reduce.
+                    s1 %= BASE;
+                    s2 %= BASE;
+                }
+            }
+
+            ref byte bufferRef = ref MemoryMarshal.GetReference(buffer);
+
+            if (length > 0)
+            {
+                if (length >= 16)
+                {
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    length -= 16;
+                }
+
+                while (length-- > 0)
+                {
+                    s2 += s1 += Unsafe.Add(ref bufferRef, index++);
+                }
+
+                if (s1 >= BASE)
+                {
+                    s1 -= BASE;
+                }
+
+                s2 %= BASE;
+            }
+
+            return s1 | (s2 << 16);
+        }
+#endif
+
+        private static uint CalculateScalar(uint adler, ReadOnlySpan<byte> buffer)
+        {
+            uint s1 = adler & 0xFFFF;
+            uint s2 = (adler >> 16) & 0xFFFF;
+            uint k;
+
+            ref byte bufferRef = ref MemoryMarshal.GetReference<byte>(buffer);
+            uint length = (uint)buffer.Length;
+            int index = 0;
+
+            while (length > 0)
+            {
+                k = length < NMAX ? length : NMAX;
+                length -= k;
+
+                while (k >= 16)
+                {
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    s1 += Unsafe.Add(ref bufferRef, index++);
+                    s2 += s1;
+                    k -= 16;
+                }
+
+                if (k != 0)
+                {
+                    do
+                    {
+                        s1 += Unsafe.Add(ref bufferRef, index++);
+                        s2 += s1;
+                    }
+                    while (--k != 0);
+                }
+
+                s1 %= BASE;
+                s2 %= BASE;
+            }
+
+            return (s2 << 16) | s1;
+        }
+    }
+}

src/SharpCompress/Archives/AbstractArchive.cs

@@ -14,11 +14,11 @@ namespace SharpCompress.Archives
         private readonly LazyReadOnlyCollection<TVolume> lazyVolumes;
         private readonly LazyReadOnlyCollection<TEntry> lazyEntries;
 
-        public event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>> EntryExtractionBegin;
-        public event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>> EntryExtractionEnd;
+        public event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>>? EntryExtractionBegin;
+        public event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>>? EntryExtractionEnd;
 
-        public event EventHandler<CompressedBytesReadEventArgs> CompressedBytesRead;
-        public event EventHandler<FilePartExtractionBeginEventArgs> FilePartExtractionBegin;
+        public event EventHandler<CompressedBytesReadEventArgs>? CompressedBytesRead;
+        public event EventHandler<FilePartExtractionBeginEventArgs>? FilePartExtractionBegin;
 
         protected ReaderOptions ReaderOptions { get; }
 
@@ -48,12 +48,14 @@ namespace SharpCompress.Archives
             lazyEntries = new LazyReadOnlyCollection<TEntry>(LoadEntries(Volumes));
         }
 
+#nullable disable
         internal AbstractArchive(ArchiveType type)
         {
             Type = type;
             lazyVolumes = new LazyReadOnlyCollection<TVolume>(Enumerable.Empty<TVolume>());
             lazyEntries = new LazyReadOnlyCollection<TEntry>(Enumerable.Empty<TEntry>());
         }
+#nullable enable
 
         public ArchiveType Type { get; }
 
@@ -79,29 +81,29 @@ 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<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()
         {
@@ -121,21 +123,19 @@ namespace SharpCompress.Archives
 
         void IExtractionListener.FireCompressedBytesRead(long currentPartCompressedBytes, long compressedReadBytes)
         {
-            CompressedBytesRead?.Invoke(this, new CompressedBytesReadEventArgs
-            {
-                CurrentFilePartCompressedBytesRead = currentPartCompressedBytes,
-                CompressedBytesRead = compressedReadBytes
-            });
+            CompressedBytesRead?.Invoke(this, new CompressedBytesReadEventArgs(
+                currentFilePartCompressedBytesRead: currentPartCompressedBytes,
+                compressedBytesRead: compressedReadBytes
+            ));
         }
 
         void IExtractionListener.FireFilePartExtractionBegin(string name, long size, long compressedSize)
         {
-            FilePartExtractionBegin?.Invoke(this, new FilePartExtractionBeginEventArgs
-            {
-                CompressedSize = compressedSize,
-                Size = size,
-                Name = name
-            });
+            FilePartExtractionBegin?.Invoke(this, new FilePartExtractionBeginEventArgs(
+                compressedSize: compressedSize,
+                size: size,
+                name: name
+            ));
         }
 
         /// <summary>
@@ -160,7 +160,7 @@ 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

@@ -12,11 +12,28 @@ 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)
@@ -45,8 +62,17 @@ 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 +109,7 @@ 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 +128,7 @@ 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

@@ -10,7 +10,7 @@ using SharpCompress.Readers;
 
 namespace SharpCompress.Archives
 {
-    public class ArchiveFactory
+    public static class ArchiveFactory
     {
         /// <summary>
         /// Opens an Archive for random access
@@ -18,14 +18,14 @@ namespace SharpCompress.Archives
         /// <param name="stream"></param>
         /// <param name="readerOptions"></param>
         /// <returns></returns>
-        public static IArchive Open(Stream stream, ReaderOptions readerOptions = null)
+        public static IArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
             if (!stream.CanRead || !stream.CanSeek)
             {
                 throw new ArgumentException("Stream should be readable and seekable");
             }
-            readerOptions = readerOptions ?? new ReaderOptions();
+            readerOptions ??= new ReaderOptions();
             if (ZipArchive.IsZipFile(stream, null))
             {
                 stream.Seek(0, SeekOrigin.Begin);
@@ -60,25 +60,13 @@ namespace SharpCompress.Archives
 
         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>
@@ -86,7 +74,7 @@ namespace SharpCompress.Archives
         /// </summary>
         /// <param name="filePath"></param>
         /// <param name="options"></param>
-        public static IArchive Open(string filePath, ReaderOptions options = null)
+        public static IArchive Open(string filePath, ReaderOptions? options = null)
         {
             filePath.CheckNotNullOrEmpty(nameof(filePath));
             return Open(new FileInfo(filePath), options);
@@ -97,52 +85,49 @@ namespace SharpCompress.Archives
         /// </summary>
         /// <param name="fileInfo"></param>
         /// <param name="options"></param>
-        public static IArchive Open(FileInfo fileInfo, ReaderOptions options = null)
+        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 };
+
+            using var stream = fileInfo.OpenRead();
+            if (ZipArchive.IsZipFile(stream, null))
             {
-                if (ZipArchive.IsZipFile(stream, null))
-                {
-                    return ZipArchive.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");
+                return ZipArchive.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");
         }
 
         /// <summary>
         /// Extract to specific directory, retaining filename
         /// </summary>
         public static void WriteToDirectory(string sourceArchive, string destinationDirectory,
-                                            ExtractionOptions options = null)
+                                            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);
             }
         }
     }

src/SharpCompress/Archives/GZip/GZipArchive.cs

@@ -18,7 +18,7 @@ namespace SharpCompress.Archives.GZip
         /// </summary>
         /// <param name="filePath"></param>
         /// <param name="readerOptions"></param>
-        public static GZipArchive Open(string filePath, ReaderOptions readerOptions = null)
+        public static GZipArchive Open(string filePath, ReaderOptions? readerOptions = null)
         {
             filePath.CheckNotNullOrEmpty(nameof(filePath));
             return Open(new FileInfo(filePath), readerOptions ?? new ReaderOptions());
@@ -29,7 +29,7 @@ namespace SharpCompress.Archives.GZip
         /// </summary>
         /// <param name="fileInfo"></param>
         /// <param name="readerOptions"></param>
-        public static GZipArchive Open(FileInfo fileInfo, ReaderOptions readerOptions = null)
+        public static GZipArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
             return new GZipArchive(fileInfo, readerOptions ?? new ReaderOptions());
@@ -40,7 +40,7 @@ namespace SharpCompress.Archives.GZip
         /// </summary>
         /// <param name="stream"></param>
         /// <param name="readerOptions"></param>
-        public static GZipArchive Open(Stream stream, ReaderOptions readerOptions = null)
+        public static GZipArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
             return new GZipArchive(stream, readerOptions ?? new ReaderOptions());
@@ -77,10 +77,9 @@ 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)

src/SharpCompress/Archives/GZip/GZipArchiveEntry.cs

@@ -15,7 +15,7 @@ namespace SharpCompress.Archives.GZip
         public virtual Stream OpenEntryStream()
         {
             //this is to reset the stream to be read multiple times
-            var part = Parts.Single() as GZipFilePart;
+            var part = (GZipFilePart)Parts.Single();
             if (part.GetRawStream().Position != part.EntryStartPosition)
             {
                 part.GetRawStream().Position = part.EntryStartPosition;

src/SharpCompress/Archives/GZip/GZipWritableArchiveEntry.cs

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 using System.Collections.Generic;
 using System.IO;
 using SharpCompress.Common;
@@ -6,7 +8,7 @@ using SharpCompress.IO;
 
 namespace SharpCompress.Archives.GZip
 {
-    internal class GZipWritableArchiveEntry : GZipArchiveEntry, IWritableArchiveEntry
+    internal sealed class GZipWritableArchiveEntry : GZipArchiveEntry, IWritableArchiveEntry
     {
         private readonly bool closeStream;
         private readonly Stream stream;

src/SharpCompress/Archives/IArchiveEntryExtensions.cs

@@ -8,22 +8,17 @@ namespace SharpCompress.Archives
     {
         public static void WriteTo(this IArchiveEntry archiveEntry, Stream streamToWriteTo)
         {
-            if (archiveEntry.Archive.Type == ArchiveType.Rar && archiveEntry.Archive.IsSolid)
-            {
-                throw new InvalidFormatException("Cannot use Archive random access on SOLID Rar files.");
-            }
-
             if (archiveEntry.IsDirectory)
             {
                 throw new ExtractionException("Entry is a file directory and cannot be extracted.");
             }
 
-            var streamListener = archiveEntry.Archive as IArchiveExtractionListener;
+            var streamListener = (IArchiveExtractionListener)archiveEntry.Archive;
             streamListener.EnsureEntriesLoaded();
             streamListener.FireEntryExtractionBegin(archiveEntry);
             streamListener.FireFilePartExtractionBegin(archiveEntry.Key, archiveEntry.Size, archiveEntry.CompressedSize);
             var entryStream = archiveEntry.OpenEntryStream();
-            if (entryStream == null)
+            if (entryStream is null)
             {
                 return;
             }
@@ -36,12 +31,12 @@ namespace SharpCompress.Archives
             }
             streamListener.FireEntryExtractionEnd(archiveEntry);
         }
-        
+
         /// <summary>
         /// Extract to specific directory, retaining filename
         /// </summary>
         public static void WriteToDirectory(this IArchiveEntry entry, string destinationDirectory,
-                                            ExtractionOptions options = null)
+                                            ExtractionOptions? options = null)
         {
             ExtractionMethods.WriteEntryToDirectory(entry, destinationDirectory, options,
                                               entry.WriteToFile);
@@ -50,10 +45,11 @@ namespace SharpCompress.Archives
         /// <summary>
         /// Extract to specific file
         /// </summary>
-        public static void WriteToFile(this IArchiveEntry entry, string destinationFileName,
-                                       ExtractionOptions options = null)
+        public static void WriteToFile(this IArchiveEntry entry,
+                                       string destinationFileName,
+                                       ExtractionOptions? options = null)
         {
-            
+
             ExtractionMethods.WriteEntryToFile(entry, destinationFileName, options,
                                                (x, fm) =>
                                                {

src/SharpCompress/Archives/IArchiveExtensions.cs

@@ -9,7 +9,7 @@ namespace SharpCompress.Archives
         /// Extract to specific directory, retaining filename
         /// </summary>
         public static void WriteToDirectory(this IArchive archive, string destinationDirectory,
-                                            ExtractionOptions options = null)
+                                            ExtractionOptions? options = null)
         {
             foreach (IArchiveEntry entry in archive.Entries.Where(x => !x.IsDirectory))
             {

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/FileInfoRarFilePart.cs

@@ -3,9 +3,9 @@ using SharpCompress.Common.Rar.Headers;
 
 namespace SharpCompress.Archives.Rar
 {
-    internal class FileInfoRarFilePart : SeekableFilePart
+    internal sealed class FileInfoRarFilePart : SeekableFilePart
     {
-        internal FileInfoRarFilePart(FileInfoRarArchiveVolume volume, string password, MarkHeader mh, FileHeader fh, FileInfo fi)
+        internal FileInfoRarFilePart(FileInfoRarArchiveVolume volume, string? password, MarkHeader mh, FileHeader fh, FileInfo fi)
             : base(mh, fh, volume.Stream, password)
         {
             FileInfo = fi;

src/SharpCompress/Archives/Rar/RarArchive.cs

@@ -65,7 +65,7 @@ namespace SharpCompress.Archives.Rar
         /// </summary>
         /// <param name="filePath"></param>
         /// <param name="options"></param>
-        public static RarArchive Open(string filePath, ReaderOptions options = null)
+        public static RarArchive Open(string filePath, ReaderOptions? options = null)
         {
             filePath.CheckNotNullOrEmpty(nameof(filePath));
             return new RarArchive(new FileInfo(filePath), options ?? new ReaderOptions());
@@ -76,7 +76,7 @@ namespace SharpCompress.Archives.Rar
         /// </summary>
         /// <param name="fileInfo"></param>
         /// <param name="options"></param>
-        public static RarArchive Open(FileInfo fileInfo, ReaderOptions options = null)
+        public static RarArchive Open(FileInfo fileInfo, ReaderOptions? options = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
             return new RarArchive(fileInfo, options ?? new ReaderOptions());
@@ -87,7 +87,7 @@ namespace SharpCompress.Archives.Rar
         /// </summary>
         /// <param name="stream"></param>
         /// <param name="options"></param>
-        public static RarArchive Open(Stream stream, ReaderOptions options = null)
+        public static RarArchive Open(Stream stream, ReaderOptions? options = null)
         {
             stream.CheckNotNull(nameof(stream));
             return Open(stream.AsEnumerable(), options ?? new ReaderOptions());
@@ -98,7 +98,7 @@ namespace SharpCompress.Archives.Rar
         /// </summary>
         /// <param name="streams"></param>
         /// <param name="options"></param>
-        public static RarArchive Open(IEnumerable<Stream> streams, ReaderOptions options = null)
+        public static RarArchive Open(IEnumerable<Stream> streams, ReaderOptions? options = null)
         {
             streams.CheckNotNull(nameof(streams));
             return new RarArchive(streams, options ?? new ReaderOptions());
@@ -120,8 +120,8 @@ namespace SharpCompress.Archives.Rar
                 return IsRarFile(stream);
             }
         }
-        
-        public static bool IsRarFile(Stream stream, ReaderOptions options = null)
+
+        public static bool IsRarFile(Stream stream, ReaderOptions? options = null)
         {
             try
             {

src/SharpCompress/Archives/Rar/RarArchiveEntry.cs

@@ -57,25 +57,20 @@ namespace SharpCompress.Archives.Rar
 
         public Stream OpenEntryStream()
         {
-            if (archive.IsSolid)
-            {
-                throw new InvalidOperationException("Use ExtractAllEntries to extract SOLID archives.");
-            }
-
             if (IsRarV3)
             {
                 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
+            {
+                return parts.Select(fp => fp.FileHeader).Any(fh => !fh.IsSplitAfter);
+            }
         }
 
         private void CheckIncomplete()

src/SharpCompress/Archives/Rar/RarArchiveVolumeFactory.cs

@@ -23,7 +23,7 @@ namespace SharpCompress.Archives.Rar
                 yield return part;
             }
         }
-        
+
         internal static IEnumerable<RarVolume> GetParts(FileInfo fileInfo, ReaderOptions options)
         {
             FileInfoRarArchiveVolume part = new FileInfoRarArchiveVolume(fileInfo, options);
@@ -34,20 +34,20 @@ namespace SharpCompress.Archives.Rar
             {
                 yield break; //if file isn't volume then there is no reason to look
             }
-            fileInfo = GetNextFileInfo(ah, part.FileParts.FirstOrDefault() as FileInfoRarFilePart);
+            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);
+                fileInfo = GetNextFileInfo(ah, part.FileParts.FirstOrDefault() as FileInfoRarFilePart)!;
                 yield return part;
             }
         }
 
-        private static FileInfo GetNextFileInfo(ArchiveHeader ah, FileInfoRarFilePart currentFilePart)
+        private static FileInfo? GetNextFileInfo(ArchiveHeader ah, FileInfoRarFilePart? currentFilePart)
         {
-            if (currentFilePart == null)
+            if (currentFilePart is null)
             {
                 return null;
             }
@@ -68,7 +68,7 @@ namespace SharpCompress.Archives.Rar
             // .rar, .r00, .r01, ...
             string extension = currentFileInfo.Extension;
 
-            StringBuilder buffer = new StringBuilder(currentFileInfo.FullName.Length);
+            var buffer = new StringBuilder(currentFileInfo.FullName.Length);
             buffer.Append(currentFileInfo.FullName.Substring(0,
                                                              currentFileInfo.FullName.Length - extension.Length));
             if (string.Compare(extension, ".rar", StringComparison.OrdinalIgnoreCase) == 0)
@@ -77,8 +77,7 @@ namespace SharpCompress.Archives.Rar
             }
             else
             {
-                int num = 0;
-                if (int.TryParse(extension.Substring(2, 2), out num))
+                if (int.TryParse(extension.Substring(2, 2), out int num))
                 {
                     num++;
                     buffer.Append(".r");
@@ -111,12 +110,11 @@ namespace SharpCompress.Archives.Rar
             }
             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))
+            if (int.TryParse(numString, out int num))
             {
                 num++;
                 for (int i = 0; i < numString.Length - num.ToString().Length; i++)

src/SharpCompress/Archives/Rar/SeekableFilePart.cs

@@ -7,9 +7,9 @@ namespace SharpCompress.Archives.Rar
     internal class SeekableFilePart : RarFilePart
     {
         private readonly Stream stream;
-        private readonly string password;
+        private readonly string? password;
 
-        internal SeekableFilePart(MarkHeader mh, FileHeader fh, Stream stream, string password)
+        internal SeekableFilePart(MarkHeader mh, FileHeader fh, Stream stream, string? password)
             : base(mh, fh)
         {
             this.stream = stream;
@@ -21,7 +21,7 @@ namespace SharpCompress.Archives.Rar
             stream.Position = FileHeader.DataStartPosition;
             if (FileHeader.R4Salt != null)
             {
-                return new RarCryptoWrapper(stream, password, FileHeader.R4Salt);
+                return new RarCryptoWrapper(stream, password!, FileHeader.R4Salt);
             }
             return stream;
         }

src/SharpCompress/Archives/SevenZip/SevenZipArchive.cs

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -108,7 +110,7 @@ namespace SharpCompress.Archives.SevenZip
 
         private void LoadFactory(Stream stream)
         {
-            if (database == null)
+            if (database is null)
             {
                 stream.Position = 0;
                 var reader = new ArchiveReader();
@@ -129,12 +131,12 @@ namespace SharpCompress.Archives.SevenZip
             }
         }
 
-        private static readonly byte[] SIGNATURE = {(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)
         {
             BinaryReader reader = new BinaryReader(stream);
-            byte[] signatureBytes = reader.ReadBytes(6);
+            ReadOnlySpan<byte> signatureBytes = reader.ReadBytes(6);
             return signatureBytes.SequenceEqual(SIGNATURE);
         }
 
@@ -154,7 +156,7 @@ namespace SharpCompress.Archives.SevenZip
             }
         }
 
-        private class SevenZipReader : AbstractReader<SevenZipEntry, SevenZipVolume>
+        private sealed class SevenZipReader : AbstractReader<SevenZipEntry, SevenZipVolume>
         {
             private readonly SevenZipArchive archive;
             private CFolder currentFolder;
@@ -180,7 +182,7 @@ namespace SharpCompress.Archives.SevenZip
                 foreach (var group in entries.Where(x => !x.IsDirectory).GroupBy(x => x.FilePart.Folder))
                 {
                     currentFolder = group.Key;
-                    if (group.Key == null)
+                    if (group.Key is null)
                     {
                         currentStream = Stream.Null;
                     }

src/SharpCompress/Archives/Tar/TarArchive.cs

@@ -20,7 +20,7 @@ namespace SharpCompress.Archives.Tar
         /// </summary>
         /// <param name="filePath"></param>
         /// <param name="readerOptions"></param>
-        public static TarArchive Open(string filePath, ReaderOptions readerOptions = null)
+        public static TarArchive Open(string filePath, ReaderOptions? readerOptions = null)
         {
             filePath.CheckNotNullOrEmpty(nameof(filePath));
             return Open(new FileInfo(filePath), readerOptions ?? new ReaderOptions());
@@ -31,7 +31,7 @@ namespace SharpCompress.Archives.Tar
         /// </summary>
         /// <param name="fileInfo"></param>
         /// <param name="readerOptions"></param>
-        public static TarArchive Open(FileInfo fileInfo, ReaderOptions readerOptions = null)
+        public static TarArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
             return new TarArchive(fileInfo, readerOptions ?? new ReaderOptions());
@@ -42,7 +42,7 @@ namespace SharpCompress.Archives.Tar
         /// </summary>
         /// <param name="stream"></param>
         /// <param name="readerOptions"></param>
-        public static TarArchive Open(Stream stream, ReaderOptions readerOptions = null)
+        public static TarArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
             return new TarArchive(stream, readerOptions ?? new ReaderOptions());
@@ -79,7 +79,7 @@ namespace SharpCompress.Archives.Tar
             }
             return false;
         }
-        
+
         /// <summary>
         /// Constructor with a FileInfo object to an existing file.
         /// </summary>
@@ -118,8 +118,8 @@ namespace SharpCompress.Archives.Tar
         protected override IEnumerable<TarArchiveEntry> LoadEntries(IEnumerable<TarVolume> volumes)
         {
             Stream stream = volumes.Single().Stream;
-            TarHeader previousHeader = null;
-            foreach (TarHeader header in TarHeaderFactory.ReadHeader(StreamingMode.Seekable, stream, ReaderOptions.ArchiveEncoding))
+            TarHeader? previousHeader = null;
+            foreach (TarHeader? header in TarHeaderFactory.ReadHeader(StreamingMode.Seekable, stream, ReaderOptions.ArchiveEncoding))
             {
                 if (header != null)
                 {

src/SharpCompress/Archives/Tar/TarWritableArchiveEntry.cs

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 using System.Collections.Generic;
 using System.IO;
 using SharpCompress.Common;
@@ -6,7 +8,7 @@ using SharpCompress.IO;
 
 namespace SharpCompress.Archives.Tar
 {
-    internal class TarWritableArchiveEntry : TarArchiveEntry, IWritableArchiveEntry
+    internal sealed class TarWritableArchiveEntry : TarArchiveEntry, IWritableArchiveEntry
     {
         private readonly bool closeStream;
         private readonly Stream stream;

src/SharpCompress/Archives/Zip/ZipArchive.cs

@@ -15,20 +15,22 @@ namespace SharpCompress.Archives.Zip
 {
     public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
     {
+#nullable disable
         private readonly SeekableZipHeaderFactory headerFactory;
+#nullable enable
 
         /// <summary>
         /// Gets or sets the compression level applied to files added to the archive,
         /// if the compression method is set to deflate
         /// </summary>
         public CompressionLevel DeflateCompressionLevel { get; set; }
-        
+
         /// <summary>
         /// Constructor expects a filepath to an existing file.
         /// </summary>
         /// <param name="filePath"></param>
         /// <param name="readerOptions"></param>
-        public static ZipArchive Open(string filePath, ReaderOptions readerOptions = null)
+        public static ZipArchive Open(string filePath, ReaderOptions? readerOptions = null)
         {
             filePath.CheckNotNullOrEmpty(nameof(filePath));
             return Open(new FileInfo(filePath), readerOptions ?? new ReaderOptions());
@@ -39,7 +41,7 @@ namespace SharpCompress.Archives.Zip
         /// </summary>
         /// <param name="fileInfo"></param>
         /// <param name="readerOptions"></param>
-        public static ZipArchive Open(FileInfo fileInfo, ReaderOptions readerOptions = null)
+        public static ZipArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
         {
             fileInfo.CheckNotNull(nameof(fileInfo));
             return new ZipArchive(fileInfo, readerOptions ?? new ReaderOptions());
@@ -50,18 +52,18 @@ namespace SharpCompress.Archives.Zip
         /// </summary>
         /// <param name="stream"></param>
         /// <param name="readerOptions"></param>
-        public static ZipArchive Open(Stream stream, ReaderOptions readerOptions = null)
+        public static ZipArchive Open(Stream stream, ReaderOptions? readerOptions = null)
         {
             stream.CheckNotNull(nameof(stream));
             return new ZipArchive(stream, readerOptions ?? new ReaderOptions());
         }
-        
-        public static bool IsZipFile(string filePath, string password = null)
+
+        public static bool IsZipFile(string filePath, string? password = null)
         {
             return IsZipFile(new FileInfo(filePath), password);
         }
 
-        public static bool IsZipFile(FileInfo fileInfo, string password = null)
+        public static bool IsZipFile(FileInfo fileInfo, string? password = null)
         {
             if (!fileInfo.Exists)
             {
@@ -73,14 +75,13 @@ namespace SharpCompress.Archives.Zip
             }
         }
 
-        public static bool IsZipFile(Stream stream, string password = null)
+        public static bool IsZipFile(Stream stream, string? password = null)
         {
             StreamingZipHeaderFactory headerFactory = new StreamingZipHeaderFactory(password, new ArchiveEncoding());
             try
             {
-                ZipHeader header =
-                    headerFactory.ReadStreamHeader(stream).FirstOrDefault(x => x.ZipHeaderType != ZipHeaderType.Split);
-                if (header == null)
+                ZipHeader? header = headerFactory.ReadStreamHeader(stream).FirstOrDefault(x => x.ZipHeaderType != ZipHeaderType.Split);
+                if (header is null)
                 {
                     return false;
                 }
@@ -95,7 +96,7 @@ namespace SharpCompress.Archives.Zip
                 return false;
             }
         }
-        
+
         /// <summary>
         /// Constructor with a FileInfo object to an existing file.
         /// </summary>
@@ -147,13 +148,13 @@ namespace SharpCompress.Archives.Zip
                             {
                                 yield return new ZipArchiveEntry(this,
                                                                  new SeekableZipFilePart(headerFactory,
-                                                                                         h as DirectoryEntryHeader,
+                                                                                         (DirectoryEntryHeader)h,
                                                                                          stream));
                             }
                             break;
                         case ZipHeaderType.DirectoryEnd:
                             {
-                                byte[] bytes = (h as DirectoryEndHeader).Comment;
+                                byte[] bytes = ((DirectoryEndHeader)h).Comment ?? Array.Empty<byte>();
                                 volume.Comment = ReaderOptions.ArchiveEncoding.Decode(bytes);
                                 yield break;
                             }

src/SharpCompress/Archives/Zip/ZipArchiveEntry.cs

@@ -6,7 +6,7 @@ namespace SharpCompress.Archives.Zip
 {
     public class ZipArchiveEntry : ZipEntry, IArchiveEntry
     {
-        internal ZipArchiveEntry(ZipArchive archive, SeekableZipFilePart part)
+        internal ZipArchiveEntry(ZipArchive archive, SeekableZipFilePart? part)
             : base(part)
         {
             Archive = archive;
@@ -25,6 +25,6 @@ namespace SharpCompress.Archives.Zip
 
         #endregion
 
-        public string Comment => (Parts.Single() as SeekableZipFilePart).Comment;
+        public string? Comment => ((SeekableZipFilePart)Parts.Single()).Comment;
     }
 }

src/SharpCompress/Common/ArchiveEncoding.cs

@@ -18,24 +18,30 @@ namespace SharpCompress.Common
         /// <summary>
         /// Set this encoding when you want to force it for all encoding operations.
         /// </summary>
-        public Encoding Forced { get; set; }
+        public Encoding? Forced { get; set; }
 
         /// <summary>
         /// Set this when you want to use a custom method for all decoding operations.
         /// </summary>
         /// <returns>string Func(bytes, index, length)</returns>
-        public Func<byte[], int, int, string> CustomDecoder { get; set; }
+        public Func<byte[], int, int, string>? CustomDecoder { get; set; }
 
         public ArchiveEncoding()
+        : this(Encoding.Default, Encoding.Default)
         {
-            Default = Encoding.GetEncoding(437);
-            Password = Encoding.GetEncoding(437);
+        }
+        public ArchiveEncoding(Encoding def, Encoding password)
+        {
+            Default = def;
+            Password = password;
         }
 
+#if !NET461
         static ArchiveEncoding()
         {
             Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
         }
+#endif
 
         public string Decode(byte[] bytes)
         {

src/SharpCompress/Common/CompressedBytesReadEventArgs.cs

@@ -2,16 +2,22 @@
 
 namespace SharpCompress.Common
 {
-    public class CompressedBytesReadEventArgs : EventArgs
+    public sealed class CompressedBytesReadEventArgs : EventArgs
     {
+        public CompressedBytesReadEventArgs(long compressedBytesRead, long currentFilePartCompressedBytesRead)
+        {
+            CompressedBytesRead = compressedBytesRead;
+            CurrentFilePartCompressedBytesRead = currentFilePartCompressedBytesRead;
+        }
+
         /// <summary>
         /// Compressed bytes read for the current entry
         /// </summary>
-        public long CompressedBytesRead { get; internal set; }
+        public long CompressedBytesRead { get; }
 
         /// <summary>
         /// Current file part read for Multipart files (e.g. Rar)
         /// </summary>
-        public long CurrentFilePartCompressedBytesRead { get; internal set; }
+        public long CurrentFilePartCompressedBytesRead { get; }
     }
 }

src/SharpCompress/Common/Entry.cs

@@ -18,7 +18,7 @@ namespace SharpCompress.Common
         /// <summary>
         /// The target of a symlink entry internal to the Archive. Will be null if not a symlink.
         /// </summary>
-        public abstract string LinkTarget { get; }
+        public abstract string? LinkTarget { get; }
 
         /// <summary>
         /// The compressed file size
@@ -71,12 +71,10 @@ namespace SharpCompress.Common
         public abstract bool IsSplitAfter { get; }
 
         /// <inheritdoc/>
-        public override string ToString()
-        {
-            return Key;
-        }
+        public override string ToString() => Key;
 
         internal abstract IEnumerable<FilePart> Parts { get; }
+
         internal 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

@@ -8,28 +8,28 @@ namespace SharpCompress.Common
         /// <summary>
         /// Extract to specific directory, retaining filename
         /// </summary>
-        public static void WriteEntryToDirectory(IEntry entry, string destinationDirectory,
-                                                 ExtractionOptions options, Action<string, ExtractionOptions> write)
+        public static void WriteEntryToDirectory(IEntry entry,
+                                                 string destinationDirectory,
+                                                 ExtractionOptions? options,
+                                                 Action<string, ExtractionOptions?> write)
         {
             string destinationFileName;
             string file = Path.GetFileName(entry.Key);
             string fullDestinationDirectoryPath = Path.GetFullPath(destinationDirectory);
 
-            options = options ?? new ExtractionOptions()
-                                 {
-                                     Overwrite = true
-                                 };
+            options ??= new ExtractionOptions()
+            {
+                Overwrite = true
+            };
 
             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.");
                     }
@@ -39,7 +39,7 @@ namespace SharpCompress.Common
                 destinationFileName = Path.Combine(destdir, file);
             }
             else
-            {        
+            {
                 destinationFileName = Path.Combine(fullDestinationDirectoryPath, file);
 
             }
@@ -48,7 +48,7 @@ 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.");
                 }
@@ -59,14 +59,14 @@ namespace SharpCompress.Common
                 Directory.CreateDirectory(destinationFileName);
             }
         }
-        
+
         public static void WriteEntryToFile(IEntry entry, string destinationFileName,
-                                            ExtractionOptions options,
+                                            ExtractionOptions? options,
                                             Action<string, FileMode> openAndWrite)
         {
             if (entry.LinkTarget != null)
             {
-                if (null == options.WriteSymbolicLink)
+                if (options?.WriteSymbolicLink is null)
                 {
                     throw new ExtractionException("Entry is a symbolic link but ExtractionOptions.WriteSymbolicLink delegate is null");
                 }
@@ -75,10 +75,10 @@ namespace SharpCompress.Common
             else
             {
                 FileMode fm = FileMode.Create;
-                options = options ?? new ExtractionOptions()
-                                     {
-                                         Overwrite = true
-                                     };
+                options ??= new ExtractionOptions()
+                {
+                    Overwrite = true
+                };
 
                 if (!options.Overwrite)
                 {

src/SharpCompress/Common/ExtractionOptions.cs

@@ -1,11 +1,13 @@
-namespace SharpCompress.Common
+using System;
+
+namespace SharpCompress.Common
 {
     public class ExtractionOptions
     {
         /// <summary>
         /// overwrite target if it exists
         /// </summary>
-        public bool Overwrite  {get; set; }
+        public bool Overwrite { get; set; }
 
         /// <summary>
         /// extract with internal directory structure
@@ -29,6 +31,10 @@
         /// </summary>
         public delegate void SymbolicLinkWriterDelegate(string sourcePath, string targetPath);
 
-        public SymbolicLinkWriterDelegate WriteSymbolicLink;
+        public SymbolicLinkWriterDelegate WriteSymbolicLink =
+            (sourcePath, targetPath) =>
+            {
+                Console.WriteLine($"Could not write symlink {sourcePath} -> {targetPath}, for more information please see https://github.com/dotnet/runtime/issues/24271");
+            };
     }
 }

src/SharpCompress/Common/FilePart.cs

@@ -14,7 +14,7 @@ namespace SharpCompress.Common
         internal abstract string FilePartName { get; }
 
         internal abstract Stream GetCompressedStream();
-        internal abstract Stream GetRawStream();
+        internal abstract Stream? GetRawStream();
         internal bool Skipped { get; set; }
     }
 }

src/SharpCompress/Common/FilePartExtractionBeginEventArgs.cs

@@ -2,21 +2,28 @@
 
 namespace SharpCompress.Common
 {
-    public class FilePartExtractionBeginEventArgs : EventArgs
+    public sealed class FilePartExtractionBeginEventArgs : EventArgs
     {
+        public FilePartExtractionBeginEventArgs(string name, long size, long compressedSize)
+        {
+            Name = name;
+            Size = size;
+            CompressedSize = compressedSize;
+        }
+
         /// <summary>
         /// File name for the part for the current entry
         /// </summary>
-        public string Name { get; internal set; }
+        public string Name { get; }
 
         /// <summary>
         /// Uncompressed size of the current entry in the part
         /// </summary>
-        public long Size { get; internal set; }
+        public long Size { get; }
 
         /// <summary>
         /// Compressed size of the current entry in the part
         /// </summary>
-        public long CompressedSize { get; internal set; }
+        public long CompressedSize { get; }
     }
 }

src/SharpCompress/Common/GZip/GZipEntry.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Text;
 
 namespace SharpCompress.Common.GZip
 {
@@ -16,15 +15,15 @@ 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;
 
-        public override string LinkTarget => null;
+        public override string? LinkTarget => null;
 
         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

@@ -8,24 +8,33 @@ using SharpCompress.Compressors.Deflate;
 
 namespace SharpCompress.Common.GZip
 {
-    internal class GZipFilePart : FilePart
+    internal sealed class GZipFilePart : FilePart
     {
-        private string _name;
+        private string? _name;
         private readonly Stream _stream;
 
         internal GZipFilePart(Stream stream, ArchiveEncoding archiveEncoding)
-        : base(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;
+        internal override string FilePartName => _name!;
 
         internal override Stream GetCompressedStream()
         {
@@ -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.");
                 }
@@ -77,15 +96,15 @@ 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
             }
         }
 

src/SharpCompress/Common/IEntry.Extensions.cs

@@ -1,5 +1,4 @@
 using System.IO;
-using SharpCompress.Readers;
 
 namespace SharpCompress.Common
 {

src/SharpCompress/Common/IEntry.cs

@@ -10,7 +10,7 @@ namespace SharpCompress.Common
         long Crc { get; }
         DateTime? CreatedTime { get; }
         string Key { get; }
-        string LinkTarget { get; }
+        string? LinkTarget { get; }
         bool IsDirectory { get; }
         bool IsEncrypted { get; }
         bool IsSplitAfter { get; }

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

@@ -4,11 +4,13 @@ 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) 
+            if (IsRar5)
+            {
                 throw new InvalidFormatException("unexpected rar5 record");
+            }
         }
 
         protected override void ReadFinish(MarkingBinaryReader reader)

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

@@ -1,10 +1,12 @@
-using SharpCompress.IO;
+#nullable disable
+
+using SharpCompress.IO;
 
 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;
@@ -13,14 +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)
         {
@@ -33,12 +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

@@ -2,16 +2,16 @@ using SharpCompress.IO;
 
 namespace SharpCompress.Common.Rar.Headers
 {
-    internal class ArchiveHeader : RarHeader
+    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();
@@ -35,26 +35,33 @@ 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) throw new InvalidFormatException("expected locator record");
+            if (type != 1)
+            {
+                throw new InvalidFormatException("expected locator record");
+            }
+
             var flags = reader.ReadRarVIntUInt16();
             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;
         }
@@ -74,7 +81,7 @@ namespace SharpCompress.Common.Rar.Headers
         public bool IsVolume => HasFlag(IsRar5 ? ArchiveFlagsV5.VOLUME : ArchiveFlagsV4.VOLUME);
 
         // RAR5: Volume number field is present. True for all volumes except first.
-        public bool IsFirstVolume => IsRar5 ? VolumeNumber == null : HasFlag(ArchiveFlagsV4.FIRST_VOLUME);
+        public bool IsFirstVolume => IsRar5 ? VolumeNumber is null : HasFlag(ArchiveFlagsV4.FIRST_VOLUME);
 
         public bool IsSolid => HasFlag(IsRar5 ? ArchiveFlagsV5.SOLID : ArchiveFlagsV4.SOLID);
     }

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

@@ -5,9 +5,12 @@ namespace SharpCompress.Common.Rar.Headers
     internal class CommentHeader : RarHeader
     {
         protected CommentHeader(RarHeader header, RarCrcBinaryReader reader)
-            : base(header, reader, HeaderType.Comment) 
-        { 
-            if (IsRar5) throw new InvalidFormatException("unexpected rar5 record");
+            : base(header, reader, HeaderType.Comment)
+        {
+            if (IsRar5)
+            {
+                throw new InvalidFormatException("unexpected rar5 record");
+            }
         }
 
         protected override void ReadFinish(MarkingBinaryReader reader)

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

@@ -1,3 +1,5 @@
+#nullable disable
+
 #if !Rar2017_64bit
 using nint = System.Int32;
 using nuint = System.UInt32;
@@ -19,18 +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);
             }
@@ -47,11 +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();
             }
 
@@ -63,7 +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;
@@ -72,7 +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();
 
@@ -99,18 +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
                         {
@@ -118,7 +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
                     //                        {
@@ -129,38 +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
@@ -169,25 +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());
             }
@@ -199,7 +209,7 @@ namespace SharpCompress.Common.Rar.Headers
             {
                 // replace embedded \\ with valid filename char
                 return path.Replace('\\', '-').Replace('/', '\\');
-            } 
+            }
             return path;
         }
 
@@ -374,20 +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;
         }
 
@@ -407,7 +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)
@@ -430,8 +442,8 @@ namespace SharpCompress.Common.Rar.Headers
         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

@@ -11,71 +11,98 @@ 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) continue;
-                            b = GetByte(stream); start++;
-                            if (b != 0x21) continue;
-                            b = GetByte(stream); start++;
-                            if (b != 0x1a) continue;
-                            b = GetByte(stream); start++;
-                            if (b != 0x07) continue;
+                            if (b != 0x72)
+                            {
+                                continue;
+                            }
 
                             b = GetByte(stream); start++;
-                            if (b == 1) 
+                            if (b != 0x21)
+                            {
+                                continue;
+                            }
+
+                            b = GetByte(stream); start++;
+                            if (b != 0x1a)
+                            {
+                                continue;
+                            }
+
+                            b = GetByte(stream); start++;
+                            if (b != 0x07)
+                            {
+                                continue;
+                            }
+
+                            b = GetByte(stream); start++;
+                            if (b == 1)
                             {
                                 b = GetByte(stream); start++;
-                                if (b != 0) continue;
+                                if (b != 0)
+                                {
+                                    continue;
+                                }
+
                                 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) continue;
+                            if (b != 0x7e)
+                            {
+                                continue;
+                            }
+
                             b = GetByte(stream); start++;
-                            if (b != 0x5e) continue;
+                            if (b != 0x5e)
+                            {
+                                continue;
+                            }
+
                             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

@@ -3,12 +3,15 @@
 namespace SharpCompress.Common.Rar.Headers
 {
     // ProtectHeader is part of the Recovery Record feature
-    internal class ProtectHeader : RarHeader
+    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) throw new InvalidFormatException("unexpected rar5 record");
+            if (IsRar5)
+            {
+                throw new InvalidFormatException("unexpected rar5 record");
+            }
         }
 
         protected override void ReadFinish(MarkingBinaryReader reader)
@@ -23,6 +26,6 @@ namespace SharpCompress.Common.Rar.Headers
         internal byte Version { get; private set; }
         internal ushort RecSectors { get; private set; }
         internal uint TotalBlocks { get; private set; }
-        internal byte[] Mark { get; private set; }
+        internal byte[]? Mark { get; private set; }
     }
 }

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

@@ -11,7 +11,7 @@ namespace SharpCompress.Common.Rar.Headers
         private readonly HeaderType _headerType;
         private readonly bool _isRar5;
 
-        internal static RarHeader TryReadBase(RarCrcBinaryReader reader, bool isRar5, ArchiveEncoding archiveEncoding)
+        internal static RarHeader? TryReadBase(RarCrcBinaryReader reader, bool isRar5, ArchiveEncoding archiveEncoding)
         {
             try
             {
@@ -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

@@ -1,4 +1,3 @@
-using System;
 using System.Collections.Generic;
 using System.IO;
 using SharpCompress.IO;
@@ -26,7 +25,7 @@ namespace SharpCompress.Common.Rar.Headers
             _isRar5 = markHeader.IsRar5;
             yield return markHeader;
 
-            RarHeader header;
+            RarHeader? header;
             while ((header = TryReadNextHeader(stream)) != null)
             {
                 yield return header;
@@ -39,16 +38,16 @@ namespace SharpCompress.Common.Rar.Headers
             }
         }
 
-        private RarHeader TryReadNextHeader(Stream stream)
+        private RarHeader? TryReadNextHeader(Stream stream)
         {
             RarCrcBinaryReader reader;
-            if (!IsEncrypted) 
+            if (!IsEncrypted)
             {
                 reader = new RarCrcBinaryReader(stream);
-            } 
-            else 
+            }
+            else
             {
-                if (Options.Password == null)
+                if (Options.Password is null)
                 {
                     throw new CryptographicException("Encrypted Rar archive has no password specified.");
                 }
@@ -56,7 +55,7 @@ namespace SharpCompress.Common.Rar.Headers
             }
 
             var header = RarHeader.TryReadBase(reader, _isRar5, Options.ArchiveEncoding);
-            if (header == null)
+            if (header is null)
             {
                 return null;
             }
@@ -66,7 +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;
@@ -128,13 +127,13 @@ namespace SharpCompress.Common.Rar.Headers
                             case StreamingMode.Streaming:
                                 {
                                     var ms = new ReadOnlySubStream(reader.BaseStream, fh.CompressedSize);
-                                    if (fh.R4Salt == null)
+                                    if (fh.R4Salt is null)
                                     {
                                         fh.PackedStream = ms;
                                     }
                                     else
                                     {
-                                        fh.PackedStream = new RarCryptoWrapper(ms, Options.Password, fh.R4Salt);
+                                        fh.PackedStream = new RarCryptoWrapper(ms, Options.Password!, fh.R4Salt);
                                     }
                                 }
                                 break;
@@ -151,11 +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);
@@ -163,21 +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

@@ -5,9 +5,12 @@ namespace SharpCompress.Common.Rar.Headers
     internal class SignHeader : RarHeader
     {
         protected SignHeader(RarHeader header, RarCrcBinaryReader reader)
-            : base(header, reader, HeaderType.Sign) 
-        { 
-            if (IsRar5) throw new InvalidFormatException("unexpected rar5 record");
+            : base(header, reader, HeaderType.Sign)
+        {
+            if (IsRar5)
+            {
+                throw new InvalidFormatException("unexpected rar5 record");
+            }
         }
 
         protected override void ReadFinish(MarkingBinaryReader reader)

src/SharpCompress/Common/Rar/RarCryptoBinaryReader.cs

@@ -3,7 +3,7 @@ using System.IO;
 
 namespace SharpCompress.Common.Rar
 {
-    internal class RarCryptoBinaryReader : RarCrcBinaryReader
+    internal sealed class RarCryptoBinaryReader : RarCrcBinaryReader
     {
         private RarRijndael _rijndael;
         private byte[] _salt;
@@ -19,7 +19,9 @@ namespace SharpCompress.Common.Rar
             // coderb: not sure why this was being done at this logical point
             //SkipQueue();
             byte[] salt = ReadBytes(8);
-            InitializeAes(salt);
+
+            _salt = salt;
+            _rijndael = RarRijndael.InitializeFrom(_password, salt);
         }
 
         // track read count ourselves rather than using the underlying stream since we buffer
@@ -39,12 +41,6 @@ namespace SharpCompress.Common.Rar
 
         private bool UseEncryption => _salt != null;
 
-        internal void InitializeAes(byte[] salt)
-        {
-            _salt = salt;
-            _rijndael = RarRijndael.InitializeFrom(_password, salt);
-        }
-
         public override byte ReadByte()
         {
             if (UseEncryption)
@@ -81,7 +77,9 @@ namespace SharpCompress.Common.Rar
                     byte[] cipherText = ReadBytesNoCrc(16);
                     var readBytes = _rijndael.ProcessBlock(cipherText);
                     foreach (var readByte in readBytes)
+                    {
                         _data.Enqueue(readByte);
+                    }
                 }
             }
 

src/SharpCompress/Common/Rar/RarCryptoWrapper.cs

@@ -4,7 +4,7 @@ using System.IO;
 
 namespace SharpCompress.Common.Rar
 {
-    internal class RarCryptoWrapper : Stream
+    internal sealed class RarCryptoWrapper : Stream
     {
         private readonly Stream _actualStream;
         private readonly byte[] _salt;
@@ -35,7 +35,7 @@ namespace SharpCompress.Common.Rar
 
         public override int Read(byte[] buffer, int offset, int count)
         {
-            if (_salt == null)
+            if (_salt is null)
             {
                 return _actualStream.Read(buffer, offset, count);
             }
@@ -58,12 +58,15 @@ namespace SharpCompress.Common.Rar
 
                     var readBytes = _rijndael.ProcessBlock(cipherText);
                     foreach (var readByte in readBytes)
+                    {
                         _data.Enqueue(readByte);
-
+                    }
                 }
 
                 for (int i = 0; i < count; i++)
+                {
                     buffer[offset + i] = _data.Dequeue();
+                }
             }
             return count;
         }
@@ -88,7 +91,7 @@ namespace SharpCompress.Common.Rar
             if (_rijndael != null)
             {
                 _rijndael.Dispose();
-                _rijndael = null;
+                _rijndael = null!;
             }
             base.Dispose(disposing);
         }

src/SharpCompress/Common/Rar/RarEntry.cs

@@ -11,7 +11,7 @@ namespace SharpCompress.Common.Rar
         /// 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;
-        
+
         /// <summary>
         /// The File's 32 bit CRC Hash
         /// </summary>
@@ -22,7 +22,7 @@ namespace SharpCompress.Common.Rar
         /// </summary>
         public override string Key => FileHeader.FileName;
 
-        public override string LinkTarget => null;
+        public override string? LinkTarget => null;
 
         /// <summary>
         /// The entry last modified time in the archive, if recorded

src/SharpCompress/Common/Rar/RarFilePart.cs

@@ -19,7 +19,7 @@ namespace SharpCompress.Common.Rar
 
         internal FileHeader FileHeader { get; }
 
-        internal override Stream GetRawStream()
+        internal override Stream? GetRawStream()
         {
             return null;
         }

src/SharpCompress/Common/Rar/RarRijndael.cs

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 using System.Security.Cryptography;
 using System.Text;
 using SharpCompress.Crypto;
@@ -25,13 +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++)
             {
@@ -66,11 +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));
                 }
             }
 
@@ -85,11 +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

@@ -21,7 +21,9 @@ namespace SharpCompress.Common.Rar
             _headerFactory = new RarHeaderFactory(mode, options);
         }
 
+#nullable disable
         internal ArchiveHeader ArchiveHeader { get; private set; }
+#nullable enable
 
         internal StreamingMode Mode => _headerFactory.StreamingMode;
 
@@ -31,26 +33,26 @@ namespace SharpCompress.Common.Rar
 
         internal IEnumerable<RarFilePart> GetVolumeFileParts()
         {
-            MarkHeader lastMarkHeader = null;
+            MarkHeader? lastMarkHeader = null;
             foreach (var header in _headerFactory.ReadHeaders(Stream))
             {
                 switch (header.HeaderType)
                 {
                     case HeaderType.Mark:
-                    {
-                        lastMarkHeader = header as MarkHeader;
-                    }
+                        {
+                            lastMarkHeader = (MarkHeader)header;
+                        }
                         break;
                     case HeaderType.Archive:
-                    {
-                        ArchiveHeader = header as ArchiveHeader;
-                    }
+                        {
+                            ArchiveHeader = (ArchiveHeader)header;
+                        }
                         break;
                     case HeaderType.File:
-                    {
-                        var fh = header as FileHeader;
-                        yield return CreateFilePart(lastMarkHeader, fh);
-                    }
+                        {
+                            var fh = (FileHeader)header;
+                            yield return CreateFilePart(lastMarkHeader!, fh);
+                        }
                         break;
                 }
             }
@@ -58,7 +60,7 @@ namespace SharpCompress.Common.Rar
 
         private void EnsureArchiveHeaderLoaded()
         {
-            if (ArchiveHeader == null)
+            if (ArchiveHeader is null)
             {
                 if (Mode == StreamingMode.Streaming)
                 {

src/SharpCompress/Common/ReaderExtractionEventArgs.cs

@@ -3,15 +3,16 @@ using SharpCompress.Readers;
 
 namespace SharpCompress.Common
 {
-    public class ReaderExtractionEventArgs<T> : EventArgs
+    public sealed class ReaderExtractionEventArgs<T> : EventArgs
     {
-        internal ReaderExtractionEventArgs(T entry, ReaderProgress readerProgress = null)
+        internal ReaderExtractionEventArgs(T entry, ReaderProgress? readerProgress = null)
         {
             Item = entry;
             ReaderProgress = readerProgress;
         }
 
         public T Item { get; }
-        public ReaderProgress ReaderProgress { get; }
+
+        public ReaderProgress? ReaderProgress { get; }
     }
 }

src/SharpCompress/Common/SevenZip/ArchiveDatabase.cs

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 using System.Collections.Generic;
 using System.IO;
 using SharpCompress.Compressors.LZMA;
@@ -35,7 +37,7 @@ namespace SharpCompress.Common.SevenZip
             _packSizes.Clear();
             _packCrCs.Clear();
             _folders.Clear();
-            _numUnpackStreamsVector = null;
+            _numUnpackStreamsVector = null!;
             _files.Clear();
 
             _packStreamStartPositions.Clear();
@@ -87,7 +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)
                         {
@@ -96,7 +98,7 @@ namespace SharpCompress.Common.SevenZip
 
                         _folderStartFileIndex.Add(i); // check it
 
-                        if (_numUnpackStreamsVector[folderIndex] != 0)
+                        if (_numUnpackStreamsVector![folderIndex] != 0)
                         {
                             break;
                         }
@@ -114,7 +116,7 @@ namespace SharpCompress.Common.SevenZip
 
                 indexInFolder++;
 
-                if (indexInFolder >= _numUnpackStreamsVector[folderIndex])
+                if (indexInFolder >= _numUnpackStreamsVector![folderIndex])
                 {
                     folderIndex++;
                     indexInFolder = 0;

src/SharpCompress/Common/SevenZip/ArchiveReader.cs

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
@@ -88,7 +90,7 @@ namespace SharpCompress.Common.SevenZip
 
         private void WaitAttribute(BlockType attribute)
         {
-            for (;;)
+            for (; ; )
             {
                 BlockType? type = ReadId();
                 if (type == attribute)
@@ -450,7 +452,7 @@ namespace SharpCompress.Common.SevenZip
 #endif
 
                 BlockType? type;
-                for (;;)
+                for (; ; )
                 {
                     type = ReadId();
                     if (type == BlockType.End)
@@ -465,7 +467,7 @@ namespace SharpCompress.Common.SevenZip
                     SkipData();
                 }
 
-                if (packCrCs == null)
+                if (packCrCs is null)
                 {
                     packCrCs = new List<uint?>(numPackStreams);
                     for (int i = 0; i < numPackStreams; i++)
@@ -506,7 +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;
@@ -537,7 +539,7 @@ namespace SharpCompress.Common.SevenZip
 #endif
                 }
 
-                for (;;)
+                for (; ; )
                 {
                     BlockType? type = ReadId();
                     if (type == BlockType.End)
@@ -578,7 +580,7 @@ namespace SharpCompress.Common.SevenZip
                 numUnpackStreamsInFolders = null;
 
                 BlockType? type;
-                for (;;)
+                for (; ; )
                 {
                     type = ReadId();
                     if (type == BlockType.NumUnpackStream)
@@ -600,7 +602,7 @@ namespace SharpCompress.Common.SevenZip
 #endif
                         continue;
                     }
-                    if (type == BlockType.Crc || type == BlockType.Size)
+                    if (type is BlockType.Crc or BlockType.Size)
                     {
                         break;
                     }
@@ -611,7 +613,7 @@ namespace SharpCompress.Common.SevenZip
                     SkipData();
                 }
 
-                if (numUnpackStreamsInFolders == null)
+                if (numUnpackStreamsInFolders is null)
                 {
                     numUnpackStreamsInFolders = new List<int>(folders.Count);
                     for (int i = 0; i < folders.Count; i++)
@@ -670,7 +672,7 @@ namespace SharpCompress.Common.SevenZip
 
                 digests = null;
 
-                for (;;)
+                for (; ; )
                 {
                     if (type == BlockType.Crc)
                     {
@@ -703,7 +705,7 @@ namespace SharpCompress.Common.SevenZip
                     }
                     else if (type == BlockType.End)
                     {
-                        if (digests == null)
+                        if (digests is null)
                         {
                             digests = new List<uint?>(numDigestsTotal);
                             for (int i = 0; i < numDigestsTotal; i++)
@@ -753,7 +755,7 @@ namespace SharpCompress.Common.SevenZip
                 unpackSizes = null;
                 digests = null;
 
-                for (;;)
+                for (; ; )
                 {
                     switch (ReadId())
                     {
@@ -789,22 +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;
 
@@ -932,7 +926,7 @@ namespace SharpCompress.Common.SevenZip
                 BitVector antiFileVector = null;
                 int numEmptyStreams = 0;
 
-                for (;;)
+                for (; ; )
                 {
                     type = ReadId();
                     if (type == BlockType.End)
@@ -967,7 +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
@@ -1055,7 +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
@@ -1070,7 +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
@@ -1085,7 +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
@@ -1100,7 +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
@@ -1443,8 +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;
@@ -1487,16 +1480,11 @@ namespace SharpCompress.Common.SevenZip
 
         public void Extract(ArchiveDatabase db, int[] indices)
         {
-            int numItems;
-            bool allFilesMode = (indices == null);
-            if (allFilesMode)
-            {
-                numItems = db._files.Count;
-            }
-            else
-            {
-                numItems = indices.Length;
-            }
+            bool allFilesMode = (indices is null);
+
+            int numItems = allFilesMode
+                ? db._files.Count
+                : indices.Length;
 
             if (numItems == 0)
             {
@@ -1566,7 +1554,7 @@ namespace SharpCompress.Common.SevenZip
                 Stream s = DecoderStreamHelper.CreateDecoderStream(_stream, folderStartPackPos, packSizes,
                                                                    folderInfo, db.PasswordProvider);
                 byte[] buffer = new byte[4 << 10];
-                for (;;)
+                for (; ; )
                 {
                     int processed = s.Read(buffer, 0, buffer.Length);
                     if (processed == 0)

src/SharpCompress/Common/SevenZip/CCoderInfo.cs

@@ -1,4 +1,6 @@
-namespace SharpCompress.Common.SevenZip
+#nullable disable
+
+namespace SharpCompress.Common.SevenZip
 {
     internal class CCoderInfo
     {

src/SharpCompress/Common/SevenZip/CFileItem.cs

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 
 namespace SharpCompress.Common.SevenZip
 {

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

@@ -18,7 +18,7 @@ namespace SharpCompress.Common.SevenZip
 
         public override string Key => FilePart.Header.Name;
 
-        public override string LinkTarget => null;
+        public override string? LinkTarget => null;
 
         public override long CompressedSize => 0;
 
@@ -38,7 +38,7 @@ namespace SharpCompress.Common.SevenZip
 
         public override bool IsSplitAfter => false;
 
-        public override int? Attrib => (int)FilePart.Header.Attrib;
+        public override int? Attrib => FilePart.Header.Attrib.HasValue ? (int?)FilePart.Header.Attrib.Value : null;
 
         internal override IEnumerable<FilePart> Parts => FilePart.AsEnumerable<FilePart>();
     }

src/SharpCompress/Common/SevenZip/SevenZipFilePart.cs

@@ -25,12 +25,12 @@ namespace SharpCompress.Common.SevenZip
         }
 
         internal CFileItem Header { get; }
-        internal CFolder Folder { get; }
+        internal CFolder? Folder { get; }
         internal int Index { get; }
 
         internal override string FilePartName => Header.Name;
 
-        internal override Stream GetRawStream()
+        internal override Stream? GetRawStream()
         {
             return null;
         }
@@ -39,11 +39,11 @@ namespace SharpCompress.Common.SevenZip
         {
             if (!Header.HasStream)
             {
-                return null;
+                return null!;
             }
-            var folderStream = _database.GetFolderStream(_stream, Folder, _database.PasswordProvider);
+            var folderStream = _database.GetFolderStream(_stream, Folder!, _database.PasswordProvider);
 
-            int firstFileIndex = _database._folderStartFileIndex[_database._folders.IndexOf(Folder)];
+            int firstFileIndex = _database._folderStartFileIndex[_database._folders.IndexOf(Folder!)];
             int skipCount = Index - firstFileIndex;
             long skipSize = 0;
             for (int i = 0; i < skipCount; i++)
@@ -61,7 +61,7 @@ namespace SharpCompress.Common.SevenZip
         {
             get
             {
-                if (_type == null)
+                if (_type is null)
                 {
                     _type = GetCompression();
                 }
@@ -82,22 +82,22 @@ namespace SharpCompress.Common.SevenZip
 
         internal CompressionType GetCompression()
         {
-            var coder = Folder._coders.First();
+            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();
             }

src/SharpCompress/Common/SevenZip/SevenZipVolume.cs

@@ -1,5 +1,4 @@
 using System.IO;
-using SharpCompress.Archives;
 using SharpCompress.Readers;
 
 namespace SharpCompress.Common.SevenZip

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

@@ -1,11 +1,13 @@
-using System;
+#nullable disable
+
+using System;
 using System.Buffers.Binary;
 using System.IO;
 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);
 
@@ -196,7 +198,7 @@ namespace SharpCompress.Common.Tar.Headers
         {
             name.CopyTo(buffer);
             int i = Math.Min(length, name.Length);
-            buffer.Slice(i, length - i).Fill(0);
+            buffer.Slice(i, length - i).Clear();
         }
 
         private static void WriteStringBytes(string name, byte[] buffer, int offset, int length)
@@ -258,10 +260,16 @@ 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;
@@ -274,7 +282,7 @@ 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

@@ -1,9 +1,10 @@
-using System;
+#nullable disable
+
+using System;
 using System.Collections.Generic;
 using System.IO;
 using SharpCompress.Common.Tar.Headers;
 using SharpCompress.IO;
-using System.Text;
 
 namespace SharpCompress.Common.Tar
 {

src/SharpCompress/Common/Tar/TarFilePart.cs

@@ -4,7 +4,7 @@ using SharpCompress.IO;
 
 namespace SharpCompress.Common.Tar
 {
-    internal class TarFilePart : FilePart
+    internal sealed class TarFilePart : FilePart
     {
         private readonly Stream _seekableStream;
 
@@ -23,13 +23,13 @@ namespace SharpCompress.Common.Tar
         {
             if (_seekableStream != null)
             {
-                _seekableStream.Position = Header.DataStartPosition.Value;
-                return new ReadOnlySubStream(_seekableStream, Header.Size);
+                _seekableStream.Position = Header.DataStartPosition!.Value;
+                return new TarReadOnlySubStream(_seekableStream, Header.Size);
             }
             return Header.PackedStream;
         }
 
-        internal override Stream GetRawStream()
+        internal override Stream? GetRawStream()
         {
             return null;
         }

src/SharpCompress/Common/Tar/TarHeaderFactory.cs

@@ -2,17 +2,16 @@
 using System.IO;
 using SharpCompress.Common.Tar.Headers;
 using SharpCompress.IO;
-using System.Text;
 
 namespace SharpCompress.Common.Tar
 {
     internal static class TarHeaderFactory
     {
-        internal static IEnumerable<TarHeader> ReadHeader(StreamingMode mode, Stream stream, ArchiveEncoding archiveEncoding)
+        internal static IEnumerable<TarHeader?> ReadHeader(StreamingMode mode, Stream stream, ArchiveEncoding archiveEncoding)
         {
             while (true)
             {
-                TarHeader header = null;
+                TarHeader? header = null;
                 try
                 {
                     BinaryReader reader = new BinaryReader(stream);

src/SharpCompress/Common/Tar/TarReadOnlySubStream.cs

@@ -20,22 +20,24 @@ namespace SharpCompress.Common.Tar
             {
                 return;
             }
+
             _isDisposed = true;
+
             if (disposing)
             {
-                long skipBytes = _amountRead % 512;
-                if (skipBytes == 0)
+                // Ensure we read all remaining blocks for this entry.
+                Stream.Skip(BytesLeftToRead);
+                _amountRead += BytesLeftToRead;
+
+                // If the last block wasn't a full 512 bytes, skip the remaining padding bytes.
+                var bytesInLastBlock = _amountRead % 512;
+
+                if (bytesInLastBlock != 0)
                 {
-                    return;
+                    Stream.Skip(512 - bytesInLastBlock);
                 }
-                skipBytes = 512 - skipBytes;
-                if (skipBytes == 0)
-                {
-                    return;
-                }
-                var buffer = new byte[skipBytes];
-                Stream.ReadFully(buffer);
             }
+
             base.Dispose(disposing);
         }
 

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

@@ -33,7 +33,7 @@ namespace SharpCompress.Common.Zip.Headers
 
         public ushort CommentLength { get; private set; }
 
-        public byte[] Comment { get; private set; }
+        public byte[]? Comment { get; private set; }
 
         public ushort TotalNumberOfEntries { get; private set; }
 

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

@@ -1,6 +1,5 @@
 using System.IO;
 using System.Linq;
-using System.Text;
 
 namespace SharpCompress.Common.Zip.Headers
 {
@@ -33,7 +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
@@ -41,7 +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);
@@ -93,6 +92,6 @@ namespace SharpCompress.Common.Zip.Headers
 
         public ushort DiskNumberStart { get; set; }
 
-        public string Comment { get; private set; }
+        public string? Comment { get; private set; }
     }
 }

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

@@ -1,5 +1,4 @@
-using System;
-using System.IO;
+using System.IO;
 
 namespace SharpCompress.Common.Zip.Headers
 {

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

@@ -1,6 +1,5 @@
 using System.IO;
 using System.Linq;
-using System.Text;
 
 namespace SharpCompress.Common.Zip.Headers
 {
@@ -25,7 +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
@@ -33,7 +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);
@@ -42,7 +41,7 @@ namespace SharpCompress.Common.Zip.Headers
             {
                 Name = ArchiveEncoding.Decode(name);
             }
-            
+
             LoadExtra(extra);
 
             var unicodePathExtra = Extra.FirstOrDefault(u => u.Type == ExtraDataType.UnicodePathExtraField);

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

@@ -18,13 +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
@@ -49,14 +61,11 @@ 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();
         }
 
@@ -106,7 +115,7 @@ namespace SharpCompress.Common.Zip.Headers
                     VolumeNumber = BinaryPrimitives.ReadUInt32LittleEndian(DataBytes.AsSpan(24));
                     return;
                 default:
-                throw new ArchiveException("Unexpected size of of Zip64 extended information extra field");
+                    throw new ArchiveException("Unexpected size of of Zip64 extended information extra field");
             }
         }
 
@@ -120,30 +129,12 @@ 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/Zip64DirectoryEndHeader.cs

@@ -1,5 +1,4 @@
-using System;
-using System.IO;
+using System.IO;
 
 namespace SharpCompress.Common.Zip.Headers
 {
@@ -44,6 +43,6 @@ namespace SharpCompress.Common.Zip.Headers
 
         public long DirectoryStartOffsetRelativeToDisk { get; private set; }
 
-        public byte[] DataSector { get; private set; }
+        public byte[]? DataSector { get; private set; }
     }
 }

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

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 using System.Buffers.Binary;
 using System.Collections.Generic;
 using System.IO;
@@ -18,7 +20,7 @@ namespace SharpCompress.Common.Zip.Headers
         {
             get
             {
-                if (Name.EndsWith("/"))
+                if (Name.EndsWith('/'))
                 {
                     return true;
                 }
@@ -26,7 +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('\\');
             }
         }
 
@@ -52,7 +54,7 @@ namespace SharpCompress.Common.Zip.Headers
 
         internal PkwareTraditionalEncryptionData ComposeEncryptionData(Stream archiveStream)
         {
-            if (archiveStream == null)
+            if (archiveStream is null)
             {
                 throw new ArgumentNullException(nameof(archiveStream));
             }
@@ -60,7 +62,7 @@ namespace SharpCompress.Common.Zip.Headers
             var buffer = new byte[12];
             archiveStream.ReadFully(buffer);
 
-            PkwareTraditionalEncryptionData encryptionData = PkwareTraditionalEncryptionData.ForRead(Password, this, buffer);
+            PkwareTraditionalEncryptionData encryptionData = PkwareTraditionalEncryptionData.ForRead(Password!, this, buffer);
 
             return encryptionData;
         }

src/SharpCompress/Common/Zip/PkwareTraditionalCryptoStream.cs

@@ -40,7 +40,7 @@ namespace SharpCompress.Common.Zip
                 throw new NotSupportedException("This stream does not encrypt via Read()");
             }
 
-            if (buffer == null)
+            if (buffer is null)
             {
                 throw new ArgumentNullException(nameof(buffer));
             }
@@ -64,7 +64,7 @@ namespace SharpCompress.Common.Zip
                 return;
             }
 
-            byte[] plaintext = null;
+            byte[] plaintext;
             if (offset != 0)
             {
                 plaintext = new byte[count];

src/SharpCompress/Common/Zip/PkwareTraditionalEncryptionData.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Text;
 using SharpCompress.Common.Zip.Headers;
 using SharpCompress.Compressors.Deflate;
 
@@ -8,7 +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)
@@ -65,9 +64,9 @@ namespace SharpCompress.Common.Zip
 
         public byte[] Encrypt(byte[] plainText, int length)
         {
-            if (plainText == null)
+            if (plainText is null)
             {
-                throw new ArgumentNullException("plaintext");
+                throw new ArgumentNullException(nameof(plainText));
             }
 
             if (length > plainText.Length)

src/SharpCompress/Common/Zip/SeekableZipFilePart.cs

@@ -27,25 +27,25 @@ namespace SharpCompress.Common.Zip
             return base.GetCompressedStream();
         }
 
-        internal string Comment => (Header as DirectoryEntryHeader).Comment;
+        internal string? Comment => ((DirectoryEntryHeader)Header).Comment;
 
         private void LoadLocalHeader()
         {
             bool hasData = Header.HasData;
-            Header = _headerFactory.GetLocalHeader(BaseStream, Header as DirectoryEntryHeader);
+            Header = _headerFactory.GetLocalHeader(BaseStream, ((DirectoryEntryHeader)Header));
             Header.HasData = hasData;
         }
 
         protected override Stream CreateBaseStream()
         {
-            BaseStream.Position = Header.DataStartPosition.Value;
+            BaseStream.Position = Header.DataStartPosition!.Value;
 
             if ((Header.CompressedSize == 0)
                 && FlagUtility.HasFlag(Header.Flags, HeaderFlags.UsePostDataDescriptor)
                 && (_directoryEntryHeader?.HasData == true)
                 && (_directoryEntryHeader?.CompressedSize != 0))
             {
-                return new ReadOnlySubStream(BaseStream, _directoryEntryHeader.CompressedSize);
+                return new ReadOnlySubStream(BaseStream, _directoryEntryHeader!.CompressedSize);
             }
 
             return BaseStream;

src/SharpCompress/Common/Zip/SeekableZipHeaderFactory.cs

@@ -3,16 +3,15 @@ using System.Collections.Generic;
 using System.IO;
 using SharpCompress.Common.Zip.Headers;
 using SharpCompress.IO;
-using System.Text;
 
 namespace SharpCompress.Common.Zip
 {
-    internal class SeekableZipHeaderFactory : ZipHeaderFactory
+    internal sealed class SeekableZipHeaderFactory : ZipHeaderFactory
     {
         private const int MAX_ITERATIONS_FOR_DIRECTORY_HEADER = 4096;
         private bool _zip64;
 
-        internal SeekableZipHeaderFactory(string password, ArchiveEncoding archiveEncoding)
+        internal SeekableZipHeaderFactory(string? password, ArchiveEncoding archiveEncoding)
             : base(StreamingMode.Seekable, password, archiveEncoding)
         {
         }
@@ -35,7 +34,9 @@ namespace SharpCompress.Common.Zip
                 stream.Seek(zip64Locator.RelativeOffsetOfTheEndOfDirectoryRecord, SeekOrigin.Begin);
                 uint zip64Signature = reader.ReadUInt32();
                 if (zip64Signature != ZIP64_END_OF_CENTRAL_DIRECTORY)
+                {
                     throw new ArchiveException("Failed to locate the Zip64 Header");
+                }
 
                 var zip64Entry = new Zip64DirectoryEndHeader();
                 zip64Entry.Read(reader);
@@ -54,8 +55,10 @@ namespace SharpCompress.Common.Zip
                 var nextHeader = ReadHeader(signature, reader, _zip64);
                 position = stream.Position;
 
-                if (nextHeader == null)
+                if (nextHeader is null)
+                {
                     yield break;
+                }
 
                 if (nextHeader is DirectoryEntryHeader entryHeader)
                 {
@@ -99,7 +102,7 @@ namespace SharpCompress.Common.Zip
             BinaryReader reader = new BinaryReader(stream);
             uint signature = reader.ReadUInt32();
             var localEntryHeader = ReadHeader(signature, reader, _zip64) as LocalEntryHeader;
-            if (localEntryHeader == null)
+            if (localEntryHeader is null)
             {
                 throw new InvalidOperationException();
             }

src/SharpCompress/Common/Zip/StreamingZipFilePart.cs

@@ -5,9 +5,9 @@ using SharpCompress.IO;
 
 namespace SharpCompress.Common.Zip
 {
-    internal class StreamingZipFilePart : ZipFilePart
+    internal sealed class StreamingZipFilePart : ZipFilePart
     {
-        private Stream _decompressionStream;
+        private Stream? _decompressionStream;
 
         internal StreamingZipFilePart(ZipFileEntry header, Stream stream)
             : base(header, stream)
@@ -41,14 +41,11 @@ namespace SharpCompress.Common.Zip
             }
             if (Header.HasData && !Skipped)
             {
-                if (_decompressionStream == null)
-                {
-                    _decompressionStream = GetCompressedStream();
-                }
+                _decompressionStream ??= GetCompressedStream();
+
                 _decompressionStream.Skip();
 
-                DeflateStream deflateStream = _decompressionStream as DeflateStream;
-                if (deflateStream != null)
+                if (_decompressionStream is DeflateStream deflateStream)
                 {
                     rewindableStream.Rewind(deflateStream.InputBuffer);
                 }

src/SharpCompress/Common/Zip/StreamingZipHeaderFactory.cs

@@ -2,13 +2,12 @@
 using System.IO;
 using SharpCompress.Common.Zip.Headers;
 using SharpCompress.IO;
-using System.Text;
 
 namespace SharpCompress.Common.Zip
 {
     internal class StreamingZipHeaderFactory : ZipHeaderFactory
     {
-        internal StreamingZipHeaderFactory(string password, ArchiveEncoding archiveEncoding)
+        internal StreamingZipHeaderFactory(string? password, ArchiveEncoding archiveEncoding)
             : base(StreamingMode.Streaming, password, archiveEncoding)
         {
         }
@@ -16,9 +15,10 @@ namespace SharpCompress.Common.Zip
         internal IEnumerable<ZipHeader> ReadStreamHeader(Stream stream)
         {
             RewindableStream rewindableStream;
-            if (stream is RewindableStream)
+
+            if (stream is RewindableStream rs)
             {
-                rewindableStream = stream as RewindableStream;
+                rewindableStream = rs;
             }
             else
             {
@@ -26,12 +26,12 @@ namespace SharpCompress.Common.Zip
             }
             while (true)
             {
-                ZipHeader header = null;
+                ZipHeader? header;
                 BinaryReader reader = new BinaryReader(rewindableStream);
                 if (_lastEntryHeader != null &&
                     (FlagUtility.HasFlag(_lastEntryHeader.Flags, HeaderFlags.UsePostDataDescriptor) || _lastEntryHeader.IsZip64))
                 {
-                    reader = (_lastEntryHeader.Part as StreamingZipFilePart).FixStreamedFileLocation(ref rewindableStream);
+                    reader = ((StreamingZipFilePart)_lastEntryHeader.Part).FixStreamedFileLocation(ref rewindableStream);
                     long? pos = rewindableStream.CanSeek ? (long?)rewindableStream.Position : null;
                     uint crc = reader.ReadUInt32();
                     if (crc == POST_DATA_DESCRIPTOR)
@@ -49,7 +49,10 @@ namespace SharpCompress.Common.Zip
                 _lastEntryHeader = null;
                 uint headerBytes = reader.ReadUInt32();
                 header = ReadHeader(headerBytes, reader);
-                if (header == 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/WinzipAesEncryptionData.cs

@@ -1,3 +1,5 @@
+#nullable disable
+
 using System;
 using System.Buffers.Binary;
 using System.Security.Cryptography;
@@ -25,33 +27,27 @@ namespace SharpCompress.Common.Zip
             Initialize();
         }
 
-        internal byte[] IvBytes
-{
-    get; set;
-}
-        internal byte[] KeyBytes
-{
-    get; set;
-}
+        internal byte[] IvBytes { get; set; }
+
+        internal byte[] KeyBytes { get; set; }
 
         private int KeySizeInBytes
         {
-            get { return KeyLengthInBytes(_keySize);
-}
+            get
+            {
+                return KeyLengthInBytes(_keySize);
+            }
         }
 
         internal static int KeyLengthInBytes(WinzipAesKeySize keySize)
         {
-            switch (keySize)
+            return keySize switch
             {
-                case WinzipAesKeySize.KeySize128:
-                    return 16;
-                case WinzipAesKeySize.KeySize192:
-                    return 24;
-                case WinzipAesKeySize.KeySize256:
-                    return 32;
-            }
-            throw new InvalidOperationException();
+                WinzipAesKeySize.KeySize128 => 16,
+                WinzipAesKeySize.KeySize192 => 24,
+                WinzipAesKeySize.KeySize256 => 32,
+                _ => throw new InvalidOperationException(),
+            };
         }
 
         private void Initialize()

src/SharpCompress/Common/Zip/ZipEntry.cs

@@ -1,4 +1,6 @@
-using System;
+#nullable disable
+
+using System;
 using System.Collections.Generic;
 using SharpCompress.Common.Zip.Headers;
 
@@ -25,33 +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);
-                }
+                    {
+                        var props = new 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 == 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 ArgumentOutOfRangeException();
+                        }
 
                 }
             }

src/SharpCompress/Common/Zip/ZipHeaderFactory.cs

@@ -3,7 +3,6 @@ using System.IO;
 using System.Linq;
 using SharpCompress.Common.Zip.Headers;
 using SharpCompress.IO;
-using System.Text;
 
 namespace SharpCompress.Common.Zip
 {
@@ -19,40 +18,40 @@ namespace SharpCompress.Common.Zip
         internal const uint ZIP64_END_OF_CENTRAL_DIRECTORY = 0x06064b50;
         internal const uint ZIP64_END_OF_CENTRAL_DIRECTORY_LOCATOR = 0x07064b50;
 
-        protected LocalEntryHeader _lastEntryHeader;
-        private readonly string _password;
+        protected LocalEntryHeader? _lastEntryHeader;
+        private readonly string? _password;
         private readonly StreamingMode _mode;
         private readonly ArchiveEncoding _archiveEncoding;
 
-        protected ZipHeaderFactory(StreamingMode mode, string password, ArchiveEncoding archiveEncoding)
+        protected ZipHeaderFactory(StreamingMode mode, string? password, ArchiveEncoding archiveEncoding)
         {
             this._mode = mode;
             this._password = password;
             this._archiveEncoding = archiveEncoding;
         }
 
-        protected ZipHeader ReadHeader(uint headerBytes, BinaryReader reader, bool zip64 = false)
+        protected ZipHeader? ReadHeader(uint headerBytes, BinaryReader reader, bool zip64 = false)
         {
             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))
+                        if (FlagUtility.HasFlag(_lastEntryHeader!.Flags, HeaderFlags.UsePostDataDescriptor))
                         {
                             _lastEntryHeader.Crc = reader.ReadUInt32();
                             _lastEntryHeader.CompressedSize = zip64 ? (long)reader.ReadUInt64() : reader.ReadUInt32();
@@ -121,7 +120,7 @@ namespace SharpCompress.Common.Zip
                     throw new NotSupportedException("SharpCompress cannot currently read non-seekable Zip Streams with encrypted data that has been written in a non-seekable manner.");
                 }
 
-                if (_password == null)
+                if (_password is null)
                 {
                     throw new CryptographicException("No password supplied for encrypted zip.");
                 }
@@ -130,7 +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/Common/Zip/ZipVolume.cs

@@ -10,6 +10,6 @@ namespace SharpCompress.Common.Zip
         {
         }
 
-        public string Comment { get; internal set; }
+        public string? Comment { get; internal set; }
     }
 }

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>
@@ -87,7 +79,7 @@ namespace SharpCompress.Compressors.ADC
         /// <param name="output">Buffer to hold decompressed data</param>
         /// <param name="bufferSize">Max size for decompressed data</param>
         /// <returns>How many bytes are stored on <paramref name="output"/></returns>
-        public static int Decompress(byte[] input, out byte[] output, int bufferSize = 262144)
+        public static int Decompress(byte[] input, out byte[]? output, int bufferSize = 262144)
         {
             return Decompress(new MemoryStream(input), out output, bufferSize);
         }
@@ -99,11 +91,11 @@ namespace SharpCompress.Compressors.ADC
         /// <param name="output">Buffer to hold decompressed data</param>
         /// <param name="bufferSize">Max size for decompressed data</param>
         /// <returns>How many bytes are stored on <paramref name="output"/></returns>
-        public static int Decompress(Stream input, out byte[] output, int bufferSize = 262144)
+        public static int Decompress(Stream input, out byte[]? output, int bufferSize = 262144)
         {
             output = null;
 
-            if (input == null || input.Length == 0)
+            if (input is null || input.Length == 0)
             {
                 return 0;
             }
@@ -211,7 +203,7 @@ namespace SharpCompress.Compressors.ADC
             }
 
             output = new byte[outPosition];
-            Array.Copy(buffer, 0, output, 0, outPosition);
+            Array.Copy(buffer, output, outPosition);
             return position - start;
         }
     }