mark as 0.37.1

Prevent infinite loop when reading corrupted archive

.config/dotnet-tools.json

@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "csharpier": {
-      "version": "0.26.1",
+      "version": "0.28.1",
       "commands": [
         "dotnet-csharpier"
       ]

.editorconfig

@@ -70,7 +70,7 @@ indent_style = tab
 
 [*.{cs,csx,cake,vb,vbx}]
 # Default Severity for all .NET Code Style rules below
-dotnet_analyzer_diagnostic.severity = warning
+dotnet_analyzer_diagnostic.severity = silent
 
 ##########################################
 # File Header (Uncomment to support file headers)
@@ -269,6 +269,8 @@ dotnet_diagnostic.CA1305.severity = suggestion
 dotnet_diagnostic.CA1307.severity = suggestion
 dotnet_diagnostic.CA1309.severity = suggestion
 dotnet_diagnostic.CA1310.severity = error
+dotnet_diagnostic.CA1507.severity = suggestion
+dotnet_diagnostic.CA1513.severity = suggestion
 dotnet_diagnostic.CA1707.severity = suggestion
 dotnet_diagnostic.CA1708.severity = suggestion
 dotnet_diagnostic.CA1711.severity = suggestion
@@ -286,6 +288,7 @@ dotnet_diagnostic.CA1834.severity = error
 dotnet_diagnostic.CA1845.severity = suggestion
 dotnet_diagnostic.CA1848.severity = suggestion
 dotnet_diagnostic.CA1852.severity = suggestion
+dotnet_diagnostic.CA1860.severity = silent
 dotnet_diagnostic.CA2016.severity = suggestion
 dotnet_diagnostic.CA2201.severity = error
 dotnet_diagnostic.CA2206.severity = error
@@ -303,13 +306,12 @@ dotnet_diagnostic.CS1998.severity = error
 dotnet_diagnostic.CS8602.severity = error
 dotnet_diagnostic.CS8604.severity = error
 dotnet_diagnostic.CS8618.severity = error
-dotnet_diagnostic.CS0618.severity = error
+dotnet_diagnostic.CS0618.severity = suggestion
 dotnet_diagnostic.CS1998.severity = error
 dotnet_diagnostic.CS4014.severity = error
 dotnet_diagnostic.CS8600.severity = error
 dotnet_diagnostic.CS8603.severity = error
 dotnet_diagnostic.CS8625.severity = error
-dotnet_diagnostic.CS8981.severity = suggestion
 
 dotnet_diagnostic.BL0005.severity = suggestion
 
@@ -318,7 +320,7 @@ dotnet_diagnostic.MVC1000.severity = suggestion
 dotnet_diagnostic.RZ10012.severity = error
 
 dotnet_diagnostic.IDE0004.severity = error # redundant cast
-dotnet_diagnostic.IDE0005.severity = error
+dotnet_diagnostic.IDE0005.severity = suggestion
 dotnet_diagnostic.IDE0007.severity = error # Use var
 dotnet_diagnostic.IDE0011.severity = error # Use braces on if statements
 dotnet_diagnostic.IDE0010.severity = silent # populate switch
@@ -329,7 +331,7 @@ dotnet_diagnostic.IDE0023.severity = suggestion # use expression body for operat
 dotnet_diagnostic.IDE0024.severity = silent # expression body for operators
 dotnet_diagnostic.IDE0025.severity = suggestion # use expression body for properties
 dotnet_diagnostic.IDE0027.severity = suggestion # Use expression body for accessors
-dotnet_diagnostic.IDE0028.severity = silent
+dotnet_diagnostic.IDE0028.severity = silent # expression body for accessors
 dotnet_diagnostic.IDE0032.severity = suggestion # Use auto property
 dotnet_diagnostic.IDE0033.severity = error # prefer tuple name
 dotnet_diagnostic.IDE0037.severity = suggestion # simplify anonymous type
@@ -337,7 +339,7 @@ dotnet_diagnostic.IDE0040.severity = error # modifiers required
 dotnet_diagnostic.IDE0041.severity = error # simplify null
 dotnet_diagnostic.IDE0042.severity = error # deconstruct variable
 dotnet_diagnostic.IDE0044.severity = suggestion # make field only when possible
-dotnet_diagnostic.IDE0047.severity = suggestion # paratemeter name
+dotnet_diagnostic.IDE0047.severity = suggestion # parameter name
 dotnet_diagnostic.IDE0051.severity = error # unused field
 dotnet_diagnostic.IDE0052.severity = error # unused member
 dotnet_diagnostic.IDE0053.severity = suggestion # lambda not needed
@@ -351,11 +353,20 @@ dotnet_diagnostic.IDE0066.severity = suggestion # switch expression
 dotnet_diagnostic.IDE0072.severity = suggestion # Populate switch - forces population of all cases even when default specified
 dotnet_diagnostic.IDE0078.severity = suggestion # use pattern matching
 dotnet_diagnostic.IDE0090.severity = suggestion # new can be simplified
-dotnet_diagnostic.IDE0130.severity = error # namespace folder structure
+dotnet_diagnostic.IDE0130.severity = suggestion # namespace folder structure
 dotnet_diagnostic.IDE0160.severity = silent # Use block namespaces ARE NOT required
 dotnet_diagnostic.IDE0161.severity = error # Please use file namespaces
 dotnet_diagnostic.IDE0200.severity = suggestion # lambda not needed
 dotnet_diagnostic.IDE1006.severity = suggestion # Naming rule violation: These words cannot contain lower case characters
+dotnet_diagnostic.IDE0260.severity = suggestion # Use pattern matching
+dotnet_diagnostic.IDE0270.severity = suggestion # Null check simplifcation
+dotnet_diagnostic.IDE0290.severity = error # Primary Constructor
+dotnet_diagnostic.IDE0300.severity = suggestion # Collection
+dotnet_diagnostic.IDE0305.severity = suggestion # Collection ToList
+
+dotnet_diagnostic.NX0001.severity = error
+dotnet_diagnostic.NX0002.severity = silent
+dotnet_diagnostic.NX0003.severity = silent
 
 ##########################################
 # Styles

.github/workflows/dotnetcore.yml

@@ -15,18 +15,11 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
-    - uses: actions/setup-dotnet@v3
+    - uses: actions/setup-dotnet@v4
       with:
-        dotnet-version: 7.0.x
-    - name: NuGet Caching
-      uses: actions/cache@v3
-      with:
-        path: ~/.nuget/packages
-        key: ${{ runner.os }}-nuget-${{ hashFiles('packages.lock.json', '*/packages.lock.json') }}
-        restore-keys: |
-            ${{ runner.os }}-nuget-
+        dotnet-version: 8.0.x
     - run: dotnet run --project build/build.csproj
-    - uses: actions/upload-artifact@v3
+    - uses: actions/upload-artifact@v4
       with:
         name: ${{ matrix.os }}-sharpcompress.nupkg
         path: artifacts/*

Directory.Build.props

@@ -10,5 +10,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <RunAnalyzersDuringLiveAnalysis>False</RunAnalyzersDuringLiveAnalysis>
     <RunAnalyzersDuringBuild>False</RunAnalyzersDuringBuild>
+    <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
+    <RestorePackagesWithLockFile>true</RestorePackagesWithLockFile>
   </PropertyGroup>
 </Project>

Directory.Packages.props

@@ -0,0 +1,18 @@
+<Project>
+  <ItemGroup>
+    <PackageVersion Include="Bullseye" Version="5.0.0" />
+    <PackageVersion Include="FluentAssertions" Version="6.12.0" />
+    <PackageVersion Include="Glob" Version="1.1.9" />
+    <PackageVersion Include="Microsoft.Bcl.AsyncInterfaces" Version="8.0.0" />
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
+    <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All"/>
+    <PackageVersion Include="Mono.Posix.NETStandard" Version="1.0.0" />
+    <PackageVersion Include="SimpleExec" Version="12.0.0" />
+    <PackageVersion Include="System.Memory" Version="4.5.5" />
+    <PackageVersion Include="System.Text.Encoding.CodePages" Version="8.0.0" />
+    <PackageVersion Include="xunit" Version="2.7.1" />
+    <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.8" />
+    <PackageVersion Include="xunit.SkippableFact" Version="1.4.13" />
+    <PackageVersion Include="ZstdSharp.Port" Version="0.8.0" />
+  </ItemGroup>
+</Project>

NuGet.config

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSourceMapping>
+    <!-- key value for <packageSource> should match key values from <packageSources> element -->
+    <packageSource key="nuget.org">
+      <package pattern="*" />
+    </packageSource>
+  </packageSourceMapping>
+</configuration>

README.md

@@ -1,12 +1,12 @@
 # SharpCompress
 
-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.
+SharpCompress is a compression library in pure C# for .NET Framework 4.62, .NET Standard 2.1, .NET 6.0 and NET 8.0 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).
 
 GitHub Actions Build -
 [![SharpCompress](https://github.com/adamhathcock/sharpcompress/actions/workflows/dotnetcore.yml/badge.svg)](https://github.com/adamhathcock/sharpcompress/actions/workflows/dotnetcore.yml)
-[![Static Badge](https://img.shields.io/badge/API%20Documentation-RobiniaDocs-43bc00?logo=readme&logoColor=white)](https://www.robiniadocs.com/d/sharpcompress/api/SharpCompress.html)
+[![Static Badge](https://img.shields.io/badge/API%20Docs-DNDocs-190088?logo=readme&logoColor=white)](https://dndocs.com/d/sharpcompress/api/index.html)
 
 ## Need Help?
 
@@ -36,7 +36,7 @@ I'm always looking for help or ideas. Please submit code or email with ideas. Un
 
 ## TODOs (always lots)
 
-* RAR 5 decryption support
+* RAR 5 decryption crc check support
 * 7Zip writing
 * Zip64 (Need writing and extend Reading)
 * Multi-volume Zip support.

SharpCompress.sln

@@ -17,6 +17,9 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Config", "Config", "{CDB425
 	ProjectSection(SolutionItems) = preProject
 		Directory.Build.props = Directory.Build.props
 		global.json = global.json
+		.editorconfig = .editorconfig
+		Directory.Packages.props = Directory.Packages.props
+		NuGet.config = NuGet.config
 	EndProjectSection
 EndProject
 Global

SharpCompress.sln.DotSettings

@@ -79,6 +79,10 @@
 	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/PredefinedNamingRules/=PrivateStaticFields/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AA_BB" /&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/PredefinedNamingRules/=PrivateStaticReadonly/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AA_BB" /&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/PredefinedNamingRules/=StaticReadonly/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AA_BB" /&gt;</s:String>
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/UserRules/=15b5b1f1_002D457c_002D4ca6_002Db278_002D5615aedc07d3/@EntryIndexedValue">&lt;Policy&gt;&lt;Descriptor Staticness="Static" AccessRightKinds="Private" Description="Static readonly fields (private)"&gt;&lt;ElementKinds&gt;&lt;Kind Name="READONLY_FIELD" /&gt;&lt;/ElementKinds&gt;&lt;/Descriptor&gt;&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AA_BB" /&gt;&lt;/Policy&gt;</s:String>
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/UserRules/=4a98fdf6_002D7d98_002D4f5a_002Dafeb_002Dea44ad98c70c/@EntryIndexedValue">&lt;Policy&gt;&lt;Descriptor Staticness="Instance" AccessRightKinds="Private" Description="Instance fields (private)"&gt;&lt;ElementKinds&gt;&lt;Kind Name="FIELD" /&gt;&lt;Kind Name="READONLY_FIELD" /&gt;&lt;/ElementKinds&gt;&lt;/Descriptor&gt;&lt;Policy Inspect="True" Prefix="_" Suffix="" Style="aaBb" /&gt;&lt;/Policy&gt;</s:String>
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/UserRules/=c873eafb_002Dd57f_002D481d_002D8c93_002D77f6863c2f88/@EntryIndexedValue">&lt;Policy&gt;&lt;Descriptor Staticness="Static" AccessRightKinds="Protected, ProtectedInternal, Internal, Public, PrivateProtected" Description="Static readonly fields (not private)"&gt;&lt;ElementKinds&gt;&lt;Kind Name="READONLY_FIELD" /&gt;&lt;/ElementKinds&gt;&lt;/Descriptor&gt;&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AA_BB" /&gt;&lt;/Policy&gt;</s:String>
+	<s:String x:Key="/Default/CodeStyle/Naming/CSharpNaming/UserRules/=f9fce829_002De6f4_002D4cb2_002D80f1_002D5497c44f51df/@EntryIndexedValue">&lt;Policy&gt;&lt;Descriptor Staticness="Static" AccessRightKinds="Private" Description="Static fields (private)"&gt;&lt;ElementKinds&gt;&lt;Kind Name="FIELD" /&gt;&lt;/ElementKinds&gt;&lt;/Descriptor&gt;&lt;Policy Inspect="True" Prefix="" Suffix="" Style="AA_BB" /&gt;&lt;/Policy&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/JavaScriptNaming/UserRules/=JS_005FBLOCK_005FSCOPE_005FCONSTANT/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="aaBb" /&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/JavaScriptNaming/UserRules/=JS_005FBLOCK_005FSCOPE_005FFUNCTION/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="aaBb" /&gt;</s:String>
 	<s:String x:Key="/Default/CodeStyle/Naming/JavaScriptNaming/UserRules/=JS_005FBLOCK_005FSCOPE_005FVARIABLE/@EntryIndexedValue">&lt;Policy Inspect="True" Prefix="" Suffix="" Style="aaBb" /&gt;</s:String>
@@ -127,6 +131,7 @@
 	<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>
+	<s:Boolean x:Key="/Default/Environment/SettingsMigration/IsMigratorApplied/=JetBrains_002EReSharper_002EPsi_002ECSharp_002ECodeStyle_002ESettingsUpgrade_002EPredefinedNamingRulesToUserRulesUpgrade/@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>

build/Program.cs

@@ -61,7 +61,7 @@ Target(
 Target(
     Test,
     DependsOn(Build),
-    ForEach("net7.0", "net462"),
+    ForEach("net8.0", "net462"),
     framework =>
     {
         IEnumerable<string> GetFiles(string d)

build/build.csproj

@@ -6,9 +6,9 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Bullseye" Version="4.2.1" />
-    <PackageReference Include="Glob" Version="1.1.9" />
-    <PackageReference Include="SimpleExec" Version="11.0.0" />
+    <PackageReference Include="Bullseye" />
+    <PackageReference Include="Glob" />
+    <PackageReference Include="SimpleExec"  />
   </ItemGroup>
 
 </Project>

build/packages.lock.json

@@ -0,0 +1,25 @@
+{
+  "version": 1,
+  "dependencies": {
+    "net7.0": {
+      "Bullseye": {
+        "type": "Direct",
+        "requested": "[5.0.0, )",
+        "resolved": "5.0.0",
+        "contentHash": "bqyt+m17ym+5aN45C5oZRAjuLDt8jKiCm/ys1XfymIXSkrTFwvI/QsbY3ucPSHDz7SF7uON7B57kXFv5H2k1ew=="
+      },
+      "Glob": {
+        "type": "Direct",
+        "requested": "[1.1.9, )",
+        "resolved": "1.1.9",
+        "contentHash": "AfK5+ECWYTP7G3AAdnU8IfVj+QpGjrh9GC2mpdcJzCvtQ4pnerAGwHsxJ9D4/RnhDUz2DSzd951O/lQjQby2Sw=="
+      },
+      "SimpleExec": {
+        "type": "Direct",
+        "requested": "[12.0.0, )",
+        "resolved": "12.0.0",
+        "contentHash": "ptxlWtxC8vM6Y6e3h9ZTxBBkOWnWrm/Sa1HT+2i1xcXY3Hx2hmKDZP5RShPf8Xr9D+ivlrXNy57ktzyH8kyt+Q=="
+      }
+    }
+  }
+}

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "7.0.101",
+    "version": "8.0.100",
     "rollForward": "latestFeature"
   }
 }

src/SharpCompress/Algorithms/Adler32.cs

@@ -62,7 +62,7 @@ internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/bl
         public static int ReduceSum(Vector256<int> accumulator)
         {
             // Add upper lane to lower lane.
-            Vector128<int> vsum = Sse2.Add(accumulator.GetLower(), accumulator.GetUpper());
+            var vsum = Sse2.Add(accumulator.GetLower(), accumulator.GetUpper());
 
             // Add odd to even.
             vsum = Sse2.Add(vsum, Sse2.Shuffle(vsum, 0b_11_11_01_01));
@@ -81,7 +81,7 @@ internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/bl
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static int EvenReduceSum(Vector256<int> accumulator)
         {
-            Vector128<int> vsum = Sse2.Add(accumulator.GetLower(), accumulator.GetUpper()); // add upper lane to lower lane
+            var vsum = Sse2.Add(accumulator.GetLower(), accumulator.GetUpper()); // add upper lane to lower lane
             vsum = Sse2.Add(vsum, Sse2.Shuffle(vsum, 0b_11_10_11_10)); // add high to low
 
             // Vector128<int>.ToScalar() isn't optimized pre-net5.0 https://github.com/dotnet/runtime/pull/37882
@@ -189,29 +189,29 @@ internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/bl
     [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
     private static unsafe uint CalculateSse(uint adler, ReadOnlySpan<byte> buffer)
     {
-        uint s1 = adler & 0xFFFF;
-        uint s2 = (adler >> 16) & 0xFFFF;
+        var s1 = adler & 0xFFFF;
+        var s2 = (adler >> 16) & 0xFFFF;
 
         // Process the data in blocks.
-        uint length = (uint)buffer.Length;
-        uint blocks = length / BlockSize;
+        var length = (uint)buffer.Length;
+        var blocks = length / BlockSize;
         length -= blocks * BlockSize;
 
         fixed (byte* bufferPtr = &MemoryMarshal.GetReference(buffer))
         {
             fixed (byte* tapPtr = &MemoryMarshal.GetReference(Tap1Tap2))
             {
-                byte* localBufferPtr = bufferPtr;
+                var localBufferPtr = bufferPtr;
 
                 // _mm_setr_epi8 on x86
-                Vector128<sbyte> tap1 = Sse2.LoadVector128((sbyte*)tapPtr);
-                Vector128<sbyte> tap2 = Sse2.LoadVector128((sbyte*)(tapPtr + 0x10));
-                Vector128<byte> zero = Vector128<byte>.Zero;
+                var tap1 = Sse2.LoadVector128((sbyte*)tapPtr);
+                var tap2 = Sse2.LoadVector128((sbyte*)(tapPtr + 0x10));
+                var zero = Vector128<byte>.Zero;
                 var ones = Vector128.Create((short)1);
 
                 while (blocks > 0)
                 {
-                    uint n = NMAX / BlockSize; /* The NMAX constraint. */
+                    var n = NMAX / BlockSize; /* The NMAX constraint. */
                     if (n > blocks)
                     {
                         n = blocks;
@@ -221,15 +221,15 @@ internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/bl
 
                     // Process n blocks of data. At most NMAX data bytes can be
                     // processed before s2 must be reduced modulo BASE.
-                    Vector128<uint> v_ps = Vector128.CreateScalar(s1 * n);
-                    Vector128<uint> v_s2 = Vector128.CreateScalar(s2);
-                    Vector128<uint> v_s1 = Vector128<uint>.Zero;
+                    var v_ps = Vector128.CreateScalar(s1 * n);
+                    var v_s2 = Vector128.CreateScalar(s2);
+                    var v_s1 = Vector128<uint>.Zero;
 
                     do
                     {
                         // Load 32 input bytes.
-                        Vector128<byte> bytes1 = Sse3.LoadDquVector128(localBufferPtr);
-                        Vector128<byte> bytes2 = Sse3.LoadDquVector128(localBufferPtr + 0x10);
+                        var bytes1 = Sse3.LoadDquVector128(localBufferPtr);
+                        var bytes2 = Sse3.LoadDquVector128(localBufferPtr + 0x10);
 
                         // Add previous block byte sum to v_ps.
                         v_ps = Sse2.Add(v_ps, v_s1);
@@ -237,11 +237,11 @@ internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/bl
                         // Horizontally add the bytes for s1, multiply-adds the
                         // bytes by [ 32, 31, 30, ... ] for s2.
                         v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes1, zero).AsUInt32());
-                        Vector128<short> mad1 = Ssse3.MultiplyAddAdjacent(bytes1, tap1);
+                        var mad1 = Ssse3.MultiplyAddAdjacent(bytes1, tap1);
                         v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad1, ones).AsUInt32());
 
                         v_s1 = Sse2.Add(v_s1, Sse2.SumAbsoluteDifferences(bytes2, zero).AsUInt32());
-                        Vector128<short> mad2 = Ssse3.MultiplyAddAdjacent(bytes2, tap2);
+                        var mad2 = Ssse3.MultiplyAddAdjacent(bytes2, tap2);
                         v_s2 = Sse2.Add(v_s2, Sse2.MultiplyAddAdjacent(mad2, ones).AsUInt32());
 
                         localBufferPtr += BlockSize;
@@ -281,15 +281,15 @@ internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/bl
     [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
     public static unsafe uint CalculateAvx2(uint adler, ReadOnlySpan<byte> buffer)
     {
-        uint s1 = adler & 0xFFFF;
-        uint s2 = (adler >> 16) & 0xFFFF;
-        uint length = (uint)buffer.Length;
+        var s1 = adler & 0xFFFF;
+        var s2 = (adler >> 16) & 0xFFFF;
+        var length = (uint)buffer.Length;
 
         fixed (byte* bufferPtr = &MemoryMarshal.GetReference(buffer))
         {
-            byte* localBufferPtr = bufferPtr;
+            var localBufferPtr = bufferPtr;
 
-            Vector256<byte> zero = Vector256<byte>.Zero;
+            var zero = Vector256<byte>.Zero;
             var dot3v = Vector256.Create((short)1);
             var dot2v = Vector256.Create(
                 32,
@@ -333,29 +333,29 @@ internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/bl
 
             while (length >= 32)
             {
-                int k = length < NMAX ? (int)length : (int)NMAX;
+                var k = length < NMAX ? (int)length : (int)NMAX;
                 k -= k % 32;
                 length -= (uint)k;
 
-                Vector256<uint> vs10 = vs1;
-                Vector256<uint> vs3 = Vector256<uint>.Zero;
+                var vs10 = vs1;
+                var vs3 = Vector256<uint>.Zero;
 
                 while (k >= 32)
                 {
                     // Load 32 input bytes.
-                    Vector256<byte> block = Avx.LoadVector256(localBufferPtr);
+                    var block = Avx.LoadVector256(localBufferPtr);
 
                     // Sum of abs diff, resulting in 2 x int32's
-                    Vector256<ushort> vs1sad = Avx2.SumAbsoluteDifferences(block, zero);
+                    var vs1sad = Avx2.SumAbsoluteDifferences(block, zero);
 
                     vs1 = Avx2.Add(vs1, vs1sad.AsUInt32());
                     vs3 = Avx2.Add(vs3, vs10);
 
                     // sum 32 uint8s to 16 shorts.
-                    Vector256<short> vshortsum2 = Avx2.MultiplyAddAdjacent(block, dot2v);
+                    var vshortsum2 = Avx2.MultiplyAddAdjacent(block, dot2v);
 
                     // sum 16 shorts to 8 uint32s.
-                    Vector256<int> vsum2 = Avx2.MultiplyAddAdjacent(vshortsum2, dot3v);
+                    var vsum2 = Avx2.MultiplyAddAdjacent(vshortsum2, dot3v);
 
                     vs2 = Avx2.Add(vsum2.AsUInt32(), vs2);
                     vs10 = vs1;
@@ -434,14 +434,14 @@ internal static class Adler32 // From https://github.com/SixLabors/ImageSharp/bl
     [MethodImpl(InliningOptions.HotPath | InliningOptions.ShortMethod)]
     private static unsafe uint CalculateScalar(uint adler, ReadOnlySpan<byte> buffer)
     {
-        uint s1 = adler & 0xFFFF;
-        uint s2 = (adler >> 16) & 0xFFFF;
+        var s1 = adler & 0xFFFF;
+        var s2 = (adler >> 16) & 0xFFFF;
         uint k;
 
         fixed (byte* bufferPtr = buffer)
         {
             var localBufferPtr = bufferPtr;
-            uint length = (uint)buffer.Length;
+            var length = (uint)buffer.Length;
 
             while (length > 0)
             {

src/SharpCompress/Archives/AbstractArchive.cs

@@ -12,39 +12,35 @@ public abstract class AbstractArchive<TEntry, TVolume> : IArchive, IArchiveExtra
     where TEntry : IArchiveEntry
     where TVolume : IVolume
 {
-    private readonly LazyReadOnlyCollection<TVolume> lazyVolumes;
-    private readonly LazyReadOnlyCollection<TEntry> lazyEntries;
+    private readonly LazyReadOnlyCollection<TVolume> _lazyVolumes;
+    private readonly LazyReadOnlyCollection<TEntry> _lazyEntries;
+    private bool _disposed;
+    private readonly SourceStream? _sourceStream;
 
     public event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>>? EntryExtractionBegin;
     public event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>>? EntryExtractionEnd;
 
     public event EventHandler<CompressedBytesReadEventArgs>? CompressedBytesRead;
     public event EventHandler<FilePartExtractionBeginEventArgs>? FilePartExtractionBegin;
-
     protected ReaderOptions ReaderOptions { get; }
 
-    private bool disposed;
-    protected SourceStream SrcStream;
-
-    internal AbstractArchive(ArchiveType type, SourceStream srcStream)
+    internal AbstractArchive(ArchiveType type, SourceStream sourceStream)
     {
         Type = type;
-        ReaderOptions = srcStream.ReaderOptions;
-        SrcStream = srcStream;
-        lazyVolumes = new LazyReadOnlyCollection<TVolume>(LoadVolumes(SrcStream));
-        lazyEntries = new LazyReadOnlyCollection<TEntry>(LoadEntries(Volumes));
+        ReaderOptions = sourceStream.ReaderOptions;
+        _sourceStream = sourceStream;
+        _lazyVolumes = new LazyReadOnlyCollection<TVolume>(LoadVolumes(_sourceStream));
+        _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>());
+        ReaderOptions = new();
+        _lazyVolumes = new LazyReadOnlyCollection<TVolume>(Enumerable.Empty<TVolume>());
+        _lazyEntries = new LazyReadOnlyCollection<TEntry>(Enumerable.Empty<TEntry>());
     }
 
-#nullable enable
-
     public ArchiveType Type { get; }
 
     void IArchiveExtractionListener.FireEntryExtractionBegin(IArchiveEntry entry) =>
@@ -65,12 +61,12 @@ public abstract class AbstractArchive<TEntry, TVolume> : IArchive, IArchiveExtra
     /// <summary>
     /// Returns an ReadOnlyCollection of all the RarArchiveEntries across the one or many parts of the RarArchive.
     /// </summary>
-    public virtual ICollection<TEntry> Entries => 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 => lazyVolumes;
+    public ICollection<TVolume> Volumes => _lazyVolumes;
 
     /// <summary>
     /// The total size of the files compressed in the archive.
@@ -84,29 +80,29 @@ public abstract class AbstractArchive<TEntry, TVolume> : IArchive, IArchiveExtra
     public virtual long TotalUncompressSize =>
         Entries.Aggregate(0L, (total, cf) => total + cf.Size);
 
-    protected abstract IEnumerable<TVolume> LoadVolumes(SourceStream srcStream);
+    protected abstract IEnumerable<TVolume> LoadVolumes(SourceStream sourceStream);
     protected abstract IEnumerable<TEntry> LoadEntries(IEnumerable<TVolume> volumes);
 
     IEnumerable<IArchiveEntry> IArchive.Entries => Entries.Cast<IArchiveEntry>();
 
-    IEnumerable<IVolume> IArchive.Volumes => lazyVolumes.Cast<IVolume>();
+    IEnumerable<IVolume> IArchive.Volumes => _lazyVolumes.Cast<IVolume>();
 
     public virtual void Dispose()
     {
-        if (!disposed)
+        if (!_disposed)
         {
-            lazyVolumes.ForEach(v => v.Dispose());
-            lazyEntries.GetLoaded().Cast<Entry>().ForEach(x => x.Close());
-            SrcStream?.Dispose();
+            _lazyVolumes.ForEach(v => v.Dispose());
+            _lazyEntries.GetLoaded().Cast<Entry>().ForEach(x => x.Close());
+            _sourceStream?.Dispose();
 
-            disposed = true;
+            _disposed = true;
         }
     }
 
     void IArchiveExtractionListener.EnsureEntriesLoaded()
     {
-        lazyEntries.EnsureFullyLoaded();
-        lazyVolumes.EnsureFullyLoaded();
+        _lazyEntries.EnsureFullyLoaded();
+        _lazyVolumes.EnsureFullyLoaded();
     }
 
     void IExtractionListener.FireCompressedBytesRead(

src/SharpCompress/Archives/AbstractWritableArchive.cs

@@ -31,18 +31,18 @@ public abstract class AbstractWritableArchive<TEntry, TVolume>
         }
     }
 
-    private readonly List<TEntry> newEntries = new List<TEntry>();
-    private readonly List<TEntry> removedEntries = new List<TEntry>();
+    private readonly List<TEntry> newEntries = new();
+    private readonly List<TEntry> removedEntries = new();
 
-    private readonly List<TEntry> modifiedEntries = new List<TEntry>();
+    private readonly List<TEntry> modifiedEntries = new();
     private bool hasModifications;
     private bool pauseRebuilding;
 
     internal AbstractWritableArchive(ArchiveType type)
         : base(type) { }
 
-    internal AbstractWritableArchive(ArchiveType type, SourceStream srcStream)
-        : base(type, srcStream) { }
+    internal AbstractWritableArchive(ArchiveType type, SourceStream sourceStream)
+        : base(type, sourceStream) { }
 
     public override ICollection<TEntry> Entries
     {
@@ -120,6 +120,10 @@ public abstract class AbstractWritableArchive<TEntry, TVolume>
     {
         foreach (var path in Entries.Select(x => x.Key))
         {
+            if (path is null)
+            {
+                continue;
+            }
             var p = path.Replace('/', '\\');
             if (p.Length > 0 && p[0] == '\\')
             {

src/SharpCompress/Archives/ArchiveFactory.cs

@@ -26,8 +26,7 @@ public static class ArchiveFactory
     public static IWritableArchive Create(ArchiveType type)
     {
         var factory = Factory
-            .Factories
-            .OfType<IWriteableArchiveFactory>()
+            .Factories.OfType<IWriteableArchiveFactory>()
             .FirstOrDefault(item => item.KnownArchiveType == type);
 
         if (factory != null)

src/SharpCompress/Archives/ArchiveVolumeFactory.cs

@@ -11,7 +11,7 @@ internal abstract class ArchiveVolumeFactory
         FileInfo? item = null;
 
         //split 001, 002 ...
-        Match m = Regex.Match(part1.Name, @"^(.*\.)([0-9]+)$", RegexOptions.IgnoreCase);
+        var m = Regex.Match(part1.Name, @"^(.*\.)([0-9]+)$", RegexOptions.IgnoreCase);
         if (m.Success)
             item = new FileInfo(
                 Path.Combine(

src/SharpCompress/Archives/GZip/GZipArchive.cs

@@ -90,25 +90,23 @@ public class GZipArchive : AbstractWritableArchive<GZipArchiveEntry, GZipVolume>
     {
         stream.CheckNotNull(nameof(stream));
         return new GZipArchive(
-            new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions())
+            new SourceStream(stream, _ => null, readerOptions ?? new ReaderOptions())
         );
     }
 
-    public static GZipArchive Create() => new GZipArchive();
+    public static GZipArchive Create() => new();
 
     /// <summary>
     /// Constructor with a SourceStream able to handle FileInfo and Streams.
     /// </summary>
-    /// <param name="srcStream"></param>
-    /// <param name="options"></param>
-    internal GZipArchive(SourceStream srcStream)
-        : base(ArchiveType.Tar, srcStream) { }
+    /// <param name="sourceStream"></param>
+    private GZipArchive(SourceStream sourceStream)
+        : base(ArchiveType.Tar, sourceStream) { }
 
-    protected override IEnumerable<GZipVolume> LoadVolumes(SourceStream srcStream)
+    protected override IEnumerable<GZipVolume> LoadVolumes(SourceStream sourceStream)
     {
-        srcStream.LoadAllParts();
-        var idx = 0;
-        return srcStream.Streams.Select(a => new GZipVolume(a, ReaderOptions, idx++));
+        sourceStream.LoadAllParts();
+        return sourceStream.Streams.Select(a => new GZipVolume(a, ReaderOptions, 0));
     }
 
     public static bool IsGZipFile(string filePath) => IsGZipFile(new FileInfo(filePath));
@@ -184,7 +182,11 @@ public class GZipArchive : AbstractWritableArchive<GZipArchiveEntry, GZipVolume>
         foreach (var entry in oldEntries.Concat(newEntries).Where(x => !x.IsDirectory))
         {
             using var entryStream = entry.OpenEntryStream();
-            writer.Write(entry.Key, entryStream, entry.LastModifiedTime);
+            writer.Write(
+                entry.Key.NotNull("Entry Key is null"),
+                entryStream,
+                entry.LastModifiedTime
+            );
         }
     }
 

src/SharpCompress/Archives/GZip/GZipArchiveEntry.cs

@@ -6,7 +6,7 @@ namespace SharpCompress.Archives.GZip;
 
 public class GZipArchiveEntry : GZipEntry, IArchiveEntry
 {
-    internal GZipArchiveEntry(GZipArchive archive, GZipFilePart part)
+    internal GZipArchiveEntry(GZipArchive archive, GZipFilePart? part)
         : base(part) => Archive = archive;
 
     public virtual Stream OpenEntryStream()

src/SharpCompress/Archives/GZip/GZipWritableArchiveEntry.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.IO;
@@ -32,7 +30,7 @@ internal sealed class GZipWritableArchiveEntry : GZipArchiveEntry, IWritableArch
 
     public override long Crc => 0;
 
-    public override string Key { get; }
+    public override string? Key { get; }
 
     public override long CompressedSize => 0;
 

src/SharpCompress/Archives/IArchiveEntryExtensions.cs

@@ -17,15 +17,11 @@ public static class IArchiveEntryExtensions
         streamListener.EnsureEntriesLoaded();
         streamListener.FireEntryExtractionBegin(archiveEntry);
         streamListener.FireFilePartExtractionBegin(
-            archiveEntry.Key,
+            archiveEntry.Key ?? "Key",
             archiveEntry.Size,
             archiveEntry.CompressedSize
         );
         var entryStream = archiveEntry.OpenEntryStream();
-        if (entryStream is null)
-        {
-            return;
-        }
         using (entryStream)
         {
             using Stream s = new ListeningStream(streamListener, entryStream);

src/SharpCompress/Archives/IArchiveExtensions.cs

@@ -3,7 +3,6 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Threading;
-using System.Threading.Tasks;
 using SharpCompress.Common;
 
 namespace SharpCompress.Archives;
@@ -59,7 +58,7 @@ public static class IArchiveExtensions
             }
 
             // Create each directory
-            var path = Path.Combine(destination, entry.Key);
+            var path = Path.Combine(destination, entry.Key.NotNull("Entry Key is null"));
             if (Path.GetDirectoryName(path) is { } directory && seenDirectories.Add(path))
             {
                 Directory.CreateDirectory(directory);

src/SharpCompress/Archives/Rar/FileInfoRarArchiveVolume.cs

@@ -13,7 +13,7 @@ namespace SharpCompress.Archives.Rar;
 /// </summary>
 internal class FileInfoRarArchiveVolume : RarVolume
 {
-    internal FileInfoRarArchiveVolume(FileInfo fileInfo, ReaderOptions options, int index = 0)
+    internal FileInfoRarArchiveVolume(FileInfo fileInfo, ReaderOptions options, int index)
         : base(StreamingMode.Seekable, fileInfo.OpenRead(), FixOptions(options), index)
     {
         FileInfo = fileInfo;

src/SharpCompress/Archives/Rar/RarArchive.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -14,40 +15,39 @@ namespace SharpCompress.Archives.Rar;
 public class RarArchive : AbstractArchive<RarArchiveEntry, RarVolume>
 {
     internal Lazy<IRarUnpack> UnpackV2017 { get; } =
-        new Lazy<IRarUnpack>(() => new Compressors.Rar.UnpackV2017.Unpack());
-    internal Lazy<IRarUnpack> UnpackV1 { get; } =
-        new Lazy<IRarUnpack>(() => new Compressors.Rar.UnpackV1.Unpack());
+        new(() => new Compressors.Rar.UnpackV2017.Unpack());
+    internal Lazy<IRarUnpack> UnpackV1 { get; } = new(() => new Compressors.Rar.UnpackV1.Unpack());
 
     /// <summary>
     /// Constructor with a SourceStream able to handle FileInfo and Streams.
     /// </summary>
-    /// <param name="srcStream"></param>
-    /// <param name="options"></param>
-    internal RarArchive(SourceStream srcStream)
-        : base(ArchiveType.Rar, srcStream) { }
+    /// <param name="sourceStream"></param>
+    private RarArchive(SourceStream sourceStream)
+        : base(ArchiveType.Rar, sourceStream) { }
 
     protected override IEnumerable<RarArchiveEntry> LoadEntries(IEnumerable<RarVolume> volumes) =>
         RarArchiveEntryFactory.GetEntries(this, volumes, ReaderOptions);
 
-    protected override IEnumerable<RarVolume> LoadVolumes(SourceStream srcStream)
+    protected override IEnumerable<RarVolume> LoadVolumes(SourceStream sourceStream)
     {
-        SrcStream.LoadAllParts(); //request all streams
-        var streams = SrcStream.Streams.ToArray();
-        var idx = 0;
+        sourceStream.LoadAllParts(); //request all streams
+        var streams = sourceStream.Streams.ToArray();
+        var i = 0;
         if (streams.Length > 1 && IsRarFile(streams[1], ReaderOptions)) //test part 2 - true = multipart not split
         {
-            SrcStream.IsVolumes = true;
+            sourceStream.IsVolumes = true;
             streams[1].Position = 0;
-            SrcStream.Position = 0;
+            sourceStream.Position = 0;
 
-            return srcStream
-                .Streams
-                .Select(a => new StreamRarArchiveVolume(a, ReaderOptions, idx++));
-        }
-        else //split mode or single file
-        {
-            return new StreamRarArchiveVolume(SrcStream, ReaderOptions, idx++).AsEnumerable();
+            return sourceStream.Streams.Select(a => new StreamRarArchiveVolume(
+                a,
+                ReaderOptions,
+                i++
+            ));
         }
+
+        //split mode or single file
+        return new StreamRarArchiveVolume(sourceStream, ReaderOptions, i++).AsEnumerable();
     }
 
     protected override IReader CreateReaderForSolidExtraction()
@@ -106,7 +106,7 @@ public class RarArchive : AbstractArchive<RarArchiveEntry, RarVolume>
     public static RarArchive Open(Stream stream, ReaderOptions? options = null)
     {
         stream.CheckNotNull(nameof(stream));
-        return new RarArchive(new SourceStream(stream, i => null, options ?? new ReaderOptions()));
+        return new RarArchive(new SourceStream(stream, _ => null, options ?? new ReaderOptions()));
     }
 
     /// <summary>

src/SharpCompress/Archives/Rar/RarArchiveEntry.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -40,7 +41,10 @@ public class RarArchiveEntry : RarEntry, IArchiveEntry
         get
         {
             CheckIncomplete();
-            return parts.Select(fp => fp.FileHeader).Single(fh => !fh.IsSplitAfter).FileCrc;
+            return BitConverter.ToUInt32(
+                parts.Select(fp => fp.FileHeader).Single(fh => !fh.IsSplitAfter).FileCrc,
+                0
+            );
         }
     }
 

src/SharpCompress/Archives/Rar/RarArchiveVolumeFactory.cs

@@ -11,7 +11,7 @@ internal static class RarArchiveVolumeFactory
         FileInfo? item = null;
 
         //new style rar - ..part1 | /part01 | part001 ....
-        Match m = Regex.Match(part1.Name, @"^(.*\.part)([0-9]+)(\.rar)$", RegexOptions.IgnoreCase);
+        var m = Regex.Match(part1.Name, @"^(.*\.part)([0-9]+)(\.rar)$", RegexOptions.IgnoreCase);
         if (m.Success)
             item = new FileInfo(
                 Path.Combine(

src/SharpCompress/Archives/Rar/SeekableFilePart.cs

@@ -6,8 +6,8 @@ namespace SharpCompress.Archives.Rar;
 
 internal class SeekableFilePart : RarFilePart
 {
-    private readonly Stream stream;
-    private readonly string? password;
+    private readonly Stream _stream;
+    private readonly string? _password;
 
     internal SeekableFilePart(
         MarkHeader mh,
@@ -18,18 +18,27 @@ internal class SeekableFilePart : RarFilePart
     )
         : base(mh, fh, index)
     {
-        this.stream = stream;
-        this.password = password;
+        _stream = stream;
+        _password = password;
     }
 
     internal override Stream GetCompressedStream()
     {
-        stream.Position = FileHeader.DataStartPosition;
+        _stream.Position = FileHeader.DataStartPosition;
+
         if (FileHeader.R4Salt != null)
         {
-            return new RarCryptoWrapper(stream, password!, FileHeader.R4Salt);
+            var cryptKey = new CryptKey3(_password!);
+            return new RarCryptoWrapper(_stream, FileHeader.R4Salt, cryptKey);
         }
-        return stream;
+
+        if (FileHeader.Rar5CryptoInfo != null)
+        {
+            var cryptKey = new CryptKey5(_password!, FileHeader.Rar5CryptoInfo);
+            return new RarCryptoWrapper(_stream, FileHeader.Rar5CryptoInfo.Salt, cryptKey);
+        }
+
+        return _stream;
     }
 
     internal override string FilePartName => "Unknown Stream - File Entry: " + FileHeader.FileName;

src/SharpCompress/Archives/Rar/StreamRarArchiveVolume.cs

@@ -9,7 +9,7 @@ namespace SharpCompress.Archives.Rar;
 
 internal class StreamRarArchiveVolume : RarVolume
 {
-    internal StreamRarArchiveVolume(Stream stream, ReaderOptions options, int index = 0)
+    internal StreamRarArchiveVolume(Stream stream, ReaderOptions options, int index)
         : base(StreamingMode.Seekable, stream, options, index) { }
 
     internal override IEnumerable<RarFilePart> ReadFileParts() => GetVolumeFileParts();

src/SharpCompress/Archives/SevenZip/SevenZipArchive.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.IO;
@@ -14,14 +12,14 @@ namespace SharpCompress.Archives.SevenZip;
 
 public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVolume>
 {
-    private ArchiveDatabase database;
+    private ArchiveDatabase? _database;
 
     /// <summary>
     /// Constructor expects a filepath to an existing file.
     /// </summary>
     /// <param name="filePath"></param>
     /// <param name="readerOptions"></param>
-    public static SevenZipArchive Open(string filePath, ReaderOptions readerOptions = null)
+    public static SevenZipArchive Open(string filePath, ReaderOptions? readerOptions = null)
     {
         filePath.CheckNotNullOrEmpty("filePath");
         return Open(new FileInfo(filePath), readerOptions ?? new ReaderOptions());
@@ -32,7 +30,7 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
     /// </summary>
     /// <param name="fileInfo"></param>
     /// <param name="readerOptions"></param>
-    public static SevenZipArchive Open(FileInfo fileInfo, ReaderOptions readerOptions = null)
+    public static SevenZipArchive Open(FileInfo fileInfo, ReaderOptions? readerOptions = null)
     {
         fileInfo.CheckNotNull("fileInfo");
         return new SevenZipArchive(
@@ -51,7 +49,7 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
     /// <param name="readerOptions"></param>
     public static SevenZipArchive Open(
         IEnumerable<FileInfo> fileInfos,
-        ReaderOptions readerOptions = null
+        ReaderOptions? readerOptions = null
     )
     {
         fileInfos.CheckNotNull(nameof(fileInfos));
@@ -72,7 +70,7 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
     /// <param name="readerOptions"></param>
     public static SevenZipArchive Open(
         IEnumerable<Stream> streams,
-        ReaderOptions readerOptions = null
+        ReaderOptions? readerOptions = null
     )
     {
         streams.CheckNotNull(nameof(streams));
@@ -91,27 +89,25 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
     /// </summary>
     /// <param name="stream"></param>
     /// <param name="readerOptions"></param>
-    public static SevenZipArchive Open(Stream stream, ReaderOptions readerOptions = null)
+    public static SevenZipArchive Open(Stream stream, ReaderOptions? readerOptions = null)
     {
         stream.CheckNotNull("stream");
         return new SevenZipArchive(
-            new SourceStream(stream, i => null, readerOptions ?? new ReaderOptions())
+            new SourceStream(stream, _ => null, readerOptions ?? new ReaderOptions())
         );
     }
 
     /// <summary>
     /// Constructor with a SourceStream able to handle FileInfo and Streams.
     /// </summary>
-    /// <param name="srcStream"></param>
-    /// <param name="options"></param>
-    internal SevenZipArchive(SourceStream srcStream)
-        : base(ArchiveType.SevenZip, srcStream) { }
+    /// <param name="sourceStream"></param>
+    private SevenZipArchive(SourceStream sourceStream)
+        : base(ArchiveType.SevenZip, sourceStream) { }
 
-    protected override IEnumerable<SevenZipVolume> LoadVolumes(SourceStream srcStream)
+    protected override IEnumerable<SevenZipVolume> LoadVolumes(SourceStream sourceStream)
     {
-        SrcStream.LoadAllParts(); //request all streams
-        var idx = 0;
-        return new SevenZipVolume(srcStream, ReaderOptions, idx++).AsEnumerable(); //simple single volume or split, multivolume not supported
+        sourceStream.NotNull("SourceStream is null").LoadAllParts(); //request all streams
+        return new SevenZipVolume(sourceStream, ReaderOptions, 0).AsEnumerable(); //simple single volume or split, multivolume not supported
     }
 
     public static bool IsSevenZipFile(string filePath) => IsSevenZipFile(new FileInfo(filePath));
@@ -135,13 +131,17 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
     {
         var stream = volumes.Single().Stream;
         LoadFactory(stream);
-        var entries = new SevenZipArchiveEntry[database._files.Count];
-        for (var i = 0; i < database._files.Count; i++)
+        if (_database is null)
         {
-            var file = database._files[i];
+            return Enumerable.Empty<SevenZipArchiveEntry>();
+        }
+        var entries = new SevenZipArchiveEntry[_database._files.Count];
+        for (var i = 0; i < _database._files.Count; i++)
+        {
+            var file = _database._files[i];
             entries[i] = new SevenZipArchiveEntry(
                 this,
-                new SevenZipFilePart(stream, database, i, file, ReaderOptions.ArchiveEncoding)
+                new SevenZipFilePart(stream, _database, i, file, ReaderOptions.ArchiveEncoding)
             );
         }
         foreach (var group in entries.Where(x => !x.IsDirectory).GroupBy(x => x.FilePart.Folder))
@@ -159,12 +159,12 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
 
     private void LoadFactory(Stream stream)
     {
-        if (database is null)
+        if (_database is null)
         {
             stream.Position = 0;
             var reader = new ArchiveReader();
             reader.Open(stream);
-            database = reader.ReadDatabase(new PasswordProvider(ReaderOptions.Password));
+            _database = reader.ReadDatabase(new PasswordProvider(ReaderOptions.Password));
         }
     }
 
@@ -180,14 +180,14 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
         }
     }
 
-    private static ReadOnlySpan<byte> SIGNATURE =>
+    private static ReadOnlySpan<byte> Signature =>
         new byte[] { (byte)'7', (byte)'z', 0xBC, 0xAF, 0x27, 0x1C };
 
     private static bool SignatureMatch(Stream stream)
     {
         var reader = new BinaryReader(stream);
         ReadOnlySpan<byte> signatureBytes = reader.ReadBytes(6);
-        return signatureBytes.SequenceEqual(SIGNATURE);
+        return signatureBytes.SequenceEqual(Signature);
     }
 
     protected override IReader CreateReaderForSolidExtraction() =>
@@ -196,30 +196,24 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
     public override bool IsSolid =>
         Entries.Where(x => !x.IsDirectory).GroupBy(x => x.FilePart.Folder).Count() > 1;
 
-    public override long TotalSize
-    {
-        get
-        {
-            var i = Entries.Count;
-            return database._packSizes.Aggregate(0L, (total, packSize) => total + packSize);
-        }
-    }
+    public override long TotalSize =>
+        _database?._packSizes.Aggregate(0L, (total, packSize) => total + packSize) ?? 0;
 
     private sealed class SevenZipReader : AbstractReader<SevenZipEntry, SevenZipVolume>
     {
-        private readonly SevenZipArchive archive;
-        private CFolder currentFolder;
-        private Stream currentStream;
-        private CFileItem currentItem;
+        private readonly SevenZipArchive _archive;
+        private CFolder? _currentFolder;
+        private Stream? _currentStream;
+        private CFileItem? _currentItem;
 
         internal SevenZipReader(ReaderOptions readerOptions, SevenZipArchive archive)
-            : base(readerOptions, ArchiveType.SevenZip) => this.archive = archive;
+            : base(readerOptions, ArchiveType.SevenZip) => this._archive = archive;
 
-        public override SevenZipVolume Volume => archive.Volumes.Single();
+        public override SevenZipVolume Volume => _archive.Volumes.Single();
 
         protected override IEnumerable<SevenZipEntry> GetEntries(Stream stream)
         {
-            var entries = archive.Entries.ToList();
+            var entries = _archive.Entries.ToList();
             stream.Position = 0;
             foreach (var dir in entries.Where(x => x.IsDirectory))
             {
@@ -229,39 +223,42 @@ public class SevenZipArchive : AbstractArchive<SevenZipArchiveEntry, SevenZipVol
                 var group in entries.Where(x => !x.IsDirectory).GroupBy(x => x.FilePart.Folder)
             )
             {
-                currentFolder = group.Key;
+                _currentFolder = group.Key;
                 if (group.Key is null)
                 {
-                    currentStream = Stream.Null;
+                    _currentStream = Stream.Null;
                 }
                 else
                 {
-                    currentStream = archive
-                        .database
-                        .GetFolderStream(
-                            stream,
-                            currentFolder,
-                            new PasswordProvider(Options.Password)
-                        );
+                    _currentStream = _archive._database?.GetFolderStream(
+                        stream,
+                        _currentFolder,
+                        new PasswordProvider(Options.Password)
+                    );
                 }
                 foreach (var entry in group)
                 {
-                    currentItem = entry.FilePart.Header;
+                    _currentItem = entry.FilePart.Header;
                     yield return entry;
                 }
             }
         }
 
         protected override EntryStream GetEntryStream() =>
-            CreateEntryStream(new ReadOnlySubStream(currentStream, currentItem.Size));
+            CreateEntryStream(
+                new ReadOnlySubStream(
+                    _currentStream.NotNull("currentStream is not null"),
+                    _currentItem?.Size ?? 0
+                )
+            );
     }
 
     private class PasswordProvider : IPasswordProvider
     {
-        private readonly string _password;
+        private readonly string? _password;
 
-        public PasswordProvider(string password) => _password = password;
+        public PasswordProvider(string? password) => _password = password;
 
-        public string CryptoGetTextPassword() => _password;
+        public string? CryptoGetTextPassword() => _password;
     }
 }

src/SharpCompress/Archives/Tar/TarArchive.cs

@@ -114,7 +114,7 @@ public class TarArchive : AbstractWritableArchive<TarArchiveEntry, TarVolume>
             var tarHeader = new TarHeader(new ArchiveEncoding());
             var readSucceeded = tarHeader.Read(new BinaryReader(stream));
             var isEmptyArchive =
-                tarHeader.Name.Length == 0
+                tarHeader.Name?.Length == 0
                 && tarHeader.Size == 0
                 && Enum.IsDefined(typeof(EntryType), tarHeader.EntryType);
             return readSucceeded || isEmptyArchive;
@@ -123,22 +123,20 @@ public class TarArchive : AbstractWritableArchive<TarArchiveEntry, TarVolume>
         return false;
     }
 
-    protected override IEnumerable<TarVolume> LoadVolumes(SourceStream srcStream)
+    protected override IEnumerable<TarVolume> LoadVolumes(SourceStream sourceStream)
     {
-        SrcStream.LoadAllParts(); //request all streams
-        var idx = 0;
-        return new TarVolume(srcStream, ReaderOptions, idx++).AsEnumerable(); //simple single volume or split, multivolume not supported
+        sourceStream.NotNull("SourceStream is null").LoadAllParts(); //request all streams
+        return new TarVolume(sourceStream, ReaderOptions, 1).AsEnumerable(); //simple single volume or split, multivolume not supported
     }
 
     /// <summary>
     /// Constructor with a SourceStream able to handle FileInfo and Streams.
     /// </summary>
-    /// <param name="srcStream"></param>
-    /// <param name="options"></param>
-    internal TarArchive(SourceStream srcStream)
-        : base(ArchiveType.Tar, srcStream) { }
+    /// <param name="sourceStream"></param>
+    private TarArchive(SourceStream sourceStream)
+        : base(ArchiveType.Tar, sourceStream) { }
 
-    internal TarArchive()
+    private TarArchive()
         : base(ArchiveType.Tar) { }
 
     protected override IEnumerable<TarArchiveEntry> LoadEntries(IEnumerable<TarVolume> volumes)
@@ -192,10 +190,14 @@ public class TarArchive : AbstractWritableArchive<TarArchiveEntry, TarVolume>
                     );
                 }
             }
+            else
+            {
+                throw new IncompleteArchiveException("Failed to read TAR header");
+            }
         }
     }
 
-    public static TarArchive Create() => new TarArchive();
+    public static TarArchive Create() => new();
 
     protected override TarArchiveEntry CreateEntryInternal(
         string filePath,
@@ -225,7 +227,12 @@ public class TarArchive : AbstractWritableArchive<TarArchiveEntry, TarVolume>
         foreach (var entry in oldEntries.Concat(newEntries).Where(x => !x.IsDirectory))
         {
             using var entryStream = entry.OpenEntryStream();
-            writer.Write(entry.Key, entryStream, entry.LastModifiedTime, entry.Size);
+            writer.Write(
+                entry.Key.NotNull("Entry Key is null"),
+                entryStream,
+                entry.LastModifiedTime,
+                entry.Size
+            );
         }
     }
 

src/SharpCompress/Archives/Tar/TarArchiveEntry.cs

@@ -7,7 +7,7 @@ namespace SharpCompress.Archives.Tar;
 
 public class TarArchiveEntry : TarEntry, IArchiveEntry
 {
-    internal TarArchiveEntry(TarArchive archive, TarFilePart part, CompressionType compressionType)
+    internal TarArchiveEntry(TarArchive archive, TarFilePart? part, CompressionType compressionType)
         : base(part, compressionType) => Archive = archive;
 
     public virtual Stream OpenEntryStream() => Parts.Single().GetCompressedStream();

src/SharpCompress/Archives/Tar/TarWritableArchiveEntry.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.IO;

src/SharpCompress/Archives/Zip/ZipArchive.cs

@@ -16,10 +16,7 @@ namespace SharpCompress.Archives.Zip;
 
 public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
 {
-#nullable disable
-    private readonly SeekableZipHeaderFactory headerFactory;
-
-#nullable enable
+    private readonly SeekableZipHeaderFactory? headerFactory;
 
     /// <summary>
     /// Gets or sets the compression level applied to files added to the archive,
@@ -30,13 +27,13 @@ public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
     /// <summary>
     /// Constructor with a SourceStream able to handle FileInfo and Streams.
     /// </summary>
-    /// <param name="srcStream"></param>
+    /// <param name="sourceStream"></param>
     /// <param name="options"></param>
-    internal ZipArchive(SourceStream srcStream)
-        : base(ArchiveType.Zip, srcStream) =>
+    internal ZipArchive(SourceStream sourceStream)
+        : base(ArchiveType.Zip, sourceStream) =>
         headerFactory = new SeekableZipHeaderFactory(
-            srcStream.ReaderOptions.Password,
-            srcStream.ReaderOptions.ArchiveEncoding
+            sourceStream.ReaderOptions.Password,
+            sourceStream.ReaderOptions.ArchiveEncoding
         );
 
     /// <summary>
@@ -189,21 +186,21 @@ public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
         }
     }
 
-    protected override IEnumerable<ZipVolume> LoadVolumes(SourceStream srcStream)
+    protected override IEnumerable<ZipVolume> LoadVolumes(SourceStream stream)
     {
-        SrcStream.LoadAllParts(); //request all streams
-        SrcStream.Position = 0;
+        stream.LoadAllParts(); //request all streams
+        stream.Position = 0;
 
-        var streams = SrcStream.Streams.ToList();
+        var streams = stream.Streams.ToList();
         var idx = 0;
-        if (streams.Count > 1) //test part 2 - true = multipart not split
+        if (streams.Count() > 1) //test part 2 - true = multipart not split
         {
             streams[1].Position += 4; //skip the POST_DATA_DESCRIPTOR to prevent an exception
             var isZip = IsZipFile(streams[1], ReaderOptions.Password);
             streams[1].Position -= 4;
             if (isZip)
             {
-                SrcStream.IsVolumes = true;
+                stream.IsVolumes = true;
 
                 var tmp = streams[0]; //arcs as zip, z01 ... swap the zip the end
                 streams.RemoveAt(0);
@@ -215,7 +212,7 @@ public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
         }
 
         //split mode or single file
-        return new ZipVolume(SrcStream, ReaderOptions, idx++).AsEnumerable();
+        return new ZipVolume(stream, ReaderOptions, idx++).AsEnumerable();
     }
 
     internal ZipArchive()
@@ -224,14 +221,13 @@ public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
     protected override IEnumerable<ZipArchiveEntry> LoadEntries(IEnumerable<ZipVolume> volumes)
     {
         var vols = volumes.ToArray();
-        foreach (var h in headerFactory.ReadSeekableHeader(vols.Last().Stream))
+        foreach (var h in headerFactory.NotNull().ReadSeekableHeader(vols.Last().Stream))
         {
             if (h != null)
             {
                 switch (h.ZipHeaderType)
                 {
                     case ZipHeaderType.DirectoryEntry:
-
                         {
                             var deh = (DirectoryEntryHeader)h;
                             Stream s;
@@ -254,14 +250,14 @@ public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
 
                             yield return new ZipArchiveEntry(
                                 this,
-                                new SeekableZipFilePart(headerFactory, deh, s)
+                                new SeekableZipFilePart(headerFactory.NotNull(), deh, s)
                             );
                         }
                         break;
                     case ZipHeaderType.DirectoryEnd:
                     {
                         var bytes = ((DirectoryEndHeader)h).Comment ?? Array.Empty<byte>();
-                        volumes.Last().Comment = ReaderOptions.ArchiveEncoding.Decode(bytes);
+                        vols.Last().Comment = ReaderOptions.ArchiveEncoding.Decode(bytes);
                         yield break;
                     }
                 }
@@ -282,7 +278,11 @@ public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
         foreach (var entry in oldEntries.Concat(newEntries).Where(x => !x.IsDirectory))
         {
             using var entryStream = entry.OpenEntryStream();
-            writer.Write(entry.Key, entryStream, entry.LastModifiedTime);
+            writer.Write(
+                entry.Key.NotNull("Entry Key is null"),
+                entryStream,
+                entry.LastModifiedTime
+            );
         }
     }
 
@@ -294,7 +294,7 @@ public class ZipArchive : AbstractWritableArchive<ZipArchiveEntry, ZipVolume>
         bool closeStream
     ) => new ZipWritableArchiveEntry(this, source, filePath, size, modified, closeStream);
 
-    public static ZipArchive Create() => new ZipArchive();
+    public static ZipArchive Create() => new();
 
     protected override IReader CreateReaderForSolidExtraction()
     {

src/SharpCompress/Archives/Zip/ZipArchiveVolumeFactory.cs

@@ -12,7 +12,7 @@ internal static class ZipArchiveVolumeFactory
 
         //load files with zip/zipx first. Swapped to end once loaded in ZipArchive
         //new style .zip, z01.. | .zipx, zx01 - if the numbers go beyond 99 then they use 100 ...1000 etc
-        Match m = Regex.Match(part1.Name, @"^(.*\.)(zipx?|zx?[0-9]+)$", RegexOptions.IgnoreCase);
+        var m = Regex.Match(part1.Name, @"^(.*\.)(zipx?|zx?[0-9]+)$", RegexOptions.IgnoreCase);
         if (m.Success)
             item = new FileInfo(
                 Path.Combine(

src/SharpCompress/BufferPool.cs

@@ -0,0 +1,33 @@
+using System.Buffers;
+
+namespace SharpCompress;
+
+internal static class BufferPool
+{
+    /// <summary>
+    ///     gets a buffer from the pool
+    /// </summary>
+    /// <param name="bufferSize">size of the buffer</param>
+    /// <returns>the buffer</returns>
+    public static byte[] Rent(int bufferSize)
+    {
+#if NETCOREAPP || NETSTANDARD2_1_OR_GREATER
+        return ArrayPool<byte>.Shared.Rent(bufferSize);
+#else
+        return new byte[bufferSize];
+#endif
+    }
+
+    /// <summary>
+    ///     returns a buffer to the pool
+    /// </summary>
+    /// <param name="buffer">the buffer to return</param>
+    public static void Return(byte[] buffer)
+    {
+#if NETCOREAPP || NETSTANDARD2_1_OR_GREATER
+        ArrayPool<byte>.Shared.Return(buffer);
+#else
+        // no-op
+#endif
+    }
+}

src/SharpCompress/Common/ArchiveEncoding.cs

@@ -8,12 +8,12 @@ public class ArchiveEncoding
     /// <summary>
     /// Default encoding to use when archive format doesn't specify one.
     /// </summary>
-    public Encoding Default { get; set; }
+    public Encoding? Default { get; set; }
 
     /// <summary>
     /// ArchiveEncoding used by encryption schemes which don't comply with RFC 2898.
     /// </summary>
-    public Encoding Password { get; set; }
+    public Encoding? Password { get; set; }
 
     /// <summary>
     /// Set this encoding when you want to force it for all encoding operations.
@@ -50,6 +50,8 @@ public class ArchiveEncoding
 
     public Encoding GetEncoding() => Forced ?? Default ?? Encoding.UTF8;
 
+    public Encoding GetPasswordEncoding() => Password ?? Encoding.UTF8;
+
     public Func<byte[], int, int, string> GetDecoder() =>
         CustomDecoder ?? ((bytes, index, count) => GetEncoding().GetString(bytes, index, count));
 }

src/SharpCompress/Common/CompressionType.cs

@@ -14,5 +14,7 @@ public enum CompressionType
     LZip,
     Xz,
     Unknown,
-    Deflate64
+    Deflate64,
+    Shrink,
+    Lzw
 }

src/SharpCompress/Common/Entry.cs

@@ -14,7 +14,7 @@ public abstract class Entry : IEntry
     /// <summary>
     /// The string key of the file internal to the Archive.
     /// </summary>
-    public abstract string Key { get; }
+    public abstract string? Key { get; }
 
     /// <summary>
     /// The target of a symlink entry internal to the Archive. Will be null if not a symlink.
@@ -71,11 +71,11 @@ public abstract class Entry : IEntry
     /// </summary>
     public abstract bool IsSplitAfter { get; }
 
-    public int VolumeIndexFirst => Parts?.FirstOrDefault()?.Index ?? 0;
-    public int VolumeIndexLast => Parts?.LastOrDefault()?.Index ?? 0;
+    public int VolumeIndexFirst => Parts.FirstOrDefault()?.Index ?? 0;
+    public int VolumeIndexLast => Parts.LastOrDefault()?.Index ?? 0;
 
     /// <inheritdoc/>
-    public override string ToString() => Key;
+    public override string ToString() => Key ?? "Entry";
 
     internal abstract IEnumerable<FilePart> Parts { get; }
 

src/SharpCompress/Common/ExtractionMethods.cs

@@ -16,7 +16,7 @@ internal static class ExtractionMethods
     )
     {
         string destinationFileName;
-        string fullDestinationDirectoryPath = Path.GetFullPath(destinationDirectory);
+        var fullDestinationDirectoryPath = Path.GetFullPath(destinationDirectory);
 
         //check for trailing slash.
         if (
@@ -36,11 +36,12 @@ internal static class ExtractionMethods
 
         options ??= new ExtractionOptions() { Overwrite = true };
 
-        string file = Path.GetFileName(entry.Key);
+        var file = Path.GetFileName(entry.Key.NotNull("Entry Key is null")).NotNull("File is null");
         if (options.ExtractFullPath)
         {
-            string folder = Path.GetDirectoryName(entry.Key)!;
-            string destdir = Path.GetFullPath(Path.Combine(fullDestinationDirectoryPath, folder));
+            var folder = Path.GetDirectoryName(entry.Key.NotNull("Entry Key is null"))
+                .NotNull("Directory is null");
+            var destdir = Path.GetFullPath(Path.Combine(fullDestinationDirectoryPath, folder));
 
             if (!Directory.Exists(destdir))
             {
@@ -102,7 +103,7 @@ internal static class ExtractionMethods
         }
         else
         {
-            FileMode fm = FileMode.Create;
+            var fm = FileMode.Create;
             options ??= new ExtractionOptions() { Overwrite = true };
 
             if (!options.Overwrite)

src/SharpCompress/Common/FilePart.cs

@@ -8,7 +8,7 @@ public abstract class FilePart
 
     internal ArchiveEncoding ArchiveEncoding { get; }
 
-    internal abstract string FilePartName { get; }
+    internal abstract string? FilePartName { get; }
     public int Index { get; set; }
 
     internal abstract Stream GetCompressedStream();

src/SharpCompress/Common/GZip/GZipEntry.cs

@@ -6,23 +6,23 @@ namespace SharpCompress.Common.GZip;
 
 public class GZipEntry : Entry
 {
-    private readonly GZipFilePart _filePart;
+    private readonly GZipFilePart? _filePart;
 
-    internal GZipEntry(GZipFilePart filePart) => _filePart = filePart;
+    internal GZipEntry(GZipFilePart? filePart) => _filePart = filePart;
 
     public override CompressionType CompressionType => CompressionType.GZip;
 
-    public override long Crc => _filePart.Crc ?? 0;
+    public override long Crc => _filePart?.Crc ?? 0;
 
-    public override string Key => _filePart.FilePartName;
+    public override string? Key => _filePart?.FilePartName;
 
     public override string? LinkTarget => null;
 
     public override long CompressedSize => 0;
 
-    public override long Size => _filePart.UncompressedSize ?? 0;
+    public override long Size => _filePart?.UncompressedSize ?? 0;
 
-    public override DateTime? LastModifiedTime => _filePart.DateModified;
+    public override DateTime? LastModifiedTime => _filePart?.DateModified;
 
     public override DateTime? CreatedTime => null;
 
@@ -36,7 +36,7 @@ public class GZipEntry : Entry
 
     public override bool IsSplitAfter => false;
 
-    internal override IEnumerable<FilePart> Parts => _filePart.AsEnumerable<FilePart>();
+    internal override IEnumerable<FilePart> Parts => _filePart.Empty();
 
     internal static IEnumerable<GZipEntry> GetEntries(Stream stream, OptionsBase options)
     {

src/SharpCompress/Common/GZip/GZipFilePart.cs

@@ -34,7 +34,7 @@ internal sealed class GZipFilePart : FilePart
     internal uint? Crc { get; private set; }
     internal uint? UncompressedSize { get; private set; }
 
-    internal override string FilePartName => _name!;
+    internal override string? FilePartName => _name;
 
     internal override Stream GetCompressedStream() =>
         new DeflateStream(_stream, CompressionMode.Decompress, CompressionLevel.Default);

src/SharpCompress/Common/GZip/GZipVolume.cs

@@ -5,7 +5,7 @@ namespace SharpCompress.Common.GZip;
 
 public class GZipVolume : Volume
 {
-    public GZipVolume(Stream stream, ReaderOptions options, int index = 0)
+    public GZipVolume(Stream stream, ReaderOptions? options, int index)
         : base(stream, options, index) { }
 
     public GZipVolume(FileInfo fileInfo, ReaderOptions options)

src/SharpCompress/Common/IEntry.cs

@@ -9,7 +9,7 @@ public interface IEntry
     long CompressedSize { get; }
     long Crc { get; }
     DateTime? CreatedTime { get; }
-    string Key { get; }
+    string? Key { get; }
     string? LinkTarget { get; }
     bool IsDirectory { get; }
     bool IsEncrypted { get; }

src/SharpCompress/Common/IVolume.cs

@@ -6,5 +6,5 @@ public interface IVolume : IDisposable
 {
     int Index { get; }
 
-    string FileName { get; }
+    string? FileName { get; }
 }

src/SharpCompress/Common/OptionsBase.cs

@@ -7,5 +7,5 @@ public class OptionsBase
     /// </summary>
     public bool LeaveStreamOpen { get; set; } = true;
 
-    public ArchiveEncoding ArchiveEncoding { get; set; } = new ArchiveEncoding();
+    public ArchiveEncoding ArchiveEncoding { get; set; } = new();
 }

src/SharpCompress/Common/PasswordProtectedException.cs

@@ -1,12 +0,0 @@
-using System;
-
-namespace SharpCompress.Common;
-
-public class PasswordProtectedException : ExtractionException
-{
-    public PasswordProtectedException(string message)
-        : base(message) { }
-
-    public PasswordProtectedException(string message, Exception inner)
-        : base(message, inner) { }
-}

src/SharpCompress/Common/Rar/CryptKey3.cs

@@ -0,0 +1,84 @@
+#nullable disable
+
+using System.Security.Cryptography;
+using System.Text;
+using SharpCompress.Common.Rar.Headers;
+
+namespace SharpCompress.Common.Rar;
+
+internal class CryptKey3 : ICryptKey
+{
+    const int AES_128 = 128;
+
+    private string _password;
+
+    public CryptKey3(string password) => _password = password ?? "";
+
+    public ICryptoTransform Transformer(byte[] salt)
+    {
+        var aesIV = new byte[EncryptionConstV5.SIZE_INITV];
+
+        var rawLength = 2 * _password.Length;
+        var rawPassword = new byte[rawLength + EncryptionConstV5.SIZE_SALT30];
+        var passwordBytes = Encoding.UTF8.GetBytes(_password);
+        for (var i = 0; i < _password.Length; i++)
+        {
+            rawPassword[i * 2] = passwordBytes[i];
+            rawPassword[(i * 2) + 1] = 0;
+        }
+
+        for (var i = 0; i < salt.Length; i++)
+        {
+            rawPassword[i + rawLength] = salt[i];
+        }
+
+        var msgDigest = SHA1.Create();
+        const int noOfRounds = (1 << 18);
+        const int iblock = 3;
+
+        byte[] digest;
+        var data = new byte[(rawPassword.Length + iblock) * noOfRounds];
+
+        //TODO slow code below, find ways to optimize
+        for (var i = 0; i < noOfRounds; i++)
+        {
+            rawPassword.CopyTo(data, i * (rawPassword.Length + iblock));
+
+            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 0] = (byte)i;
+            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 1] = (byte)(i >> 8);
+            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 2] = (byte)(i >> 16);
+
+            if (i % (noOfRounds / EncryptionConstV5.SIZE_INITV) == 0)
+            {
+                digest = msgDigest.ComputeHash(data, 0, (i + 1) * (rawPassword.Length + iblock));
+                aesIV[i / (noOfRounds / EncryptionConstV5.SIZE_INITV)] = digest[19];
+            }
+        }
+        digest = msgDigest.ComputeHash(data);
+        //slow code ends
+
+        var aesKey = new byte[EncryptionConstV5.SIZE_INITV];
+        for (var i = 0; i < 4; i++)
+        {
+            for (var 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)
+                );
+            }
+        }
+
+        var aes = Aes.Create();
+        aes.KeySize = AES_128;
+        aes.Mode = CipherMode.CBC;
+        aes.Padding = PaddingMode.None;
+        aes.Key = aesKey;
+        aes.IV = aesIV;
+        return aes.CreateDecryptor();
+    }
+}

src/SharpCompress/Common/Rar/CryptKey5.cs

@@ -0,0 +1,95 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Text;
+using SharpCompress.Common.Rar.Headers;
+
+namespace SharpCompress.Common.Rar;
+
+internal class CryptKey5 : ICryptKey
+{
+    const int AES_256 = 256;
+    const int DERIVED_KEY_LENGTH = 0x10;
+    const int SHA256_DIGEST_SIZE = 32;
+
+    private string _password;
+    private Rar5CryptoInfo _cryptoInfo;
+    private byte[] _pswCheck = { };
+    private byte[] _hashKey = { };
+
+    public CryptKey5(string password, Rar5CryptoInfo rar5CryptoInfo)
+    {
+        _password = password ?? "";
+        _cryptoInfo = rar5CryptoInfo;
+    }
+
+    public byte[] PswCheck => _pswCheck;
+
+    public byte[] HashKey => _hashKey;
+
+    private static List<byte[]> GenerateRarPBKDF2Key(
+        string password,
+        byte[] salt,
+        int iterations,
+        int keyLength
+    )
+    {
+        using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(password));
+        var block = hmac.ComputeHash(salt);
+        var finalHash = (byte[])block.Clone();
+
+        var loop = new int[] { iterations, 17, 17 };
+        var res = new List<byte[]> { };
+
+        for (var x = 0; x < 3; x++)
+        {
+            for (var i = 1; i < loop[x]; i++)
+            {
+                block = hmac.ComputeHash(block);
+                for (var j = 0; j < finalHash.Length; j++)
+                {
+                    finalHash[j] ^= block[j];
+                }
+            }
+
+            res.Add((byte[])finalHash.Clone());
+        }
+
+        return res;
+    }
+
+    public ICryptoTransform Transformer(byte[] salt)
+    {
+        var iterations = (1 << _cryptoInfo.LG2Count); // Adjust the number of iterations as needed
+
+        var salt_rar5 = salt.Concat(new byte[] { 0, 0, 0, 1 });
+        var derivedKey = GenerateRarPBKDF2Key(
+            _password,
+            salt_rar5.ToArray(),
+            iterations,
+            DERIVED_KEY_LENGTH
+        );
+
+        _hashKey = derivedKey[1];
+
+        _pswCheck = new byte[EncryptionConstV5.SIZE_PSWCHECK];
+
+        for (var i = 0; i < SHA256_DIGEST_SIZE; i++)
+        {
+            _pswCheck[i % EncryptionConstV5.SIZE_PSWCHECK] ^= derivedKey[2][i];
+        }
+
+        if (_cryptoInfo.UsePswCheck && !_cryptoInfo.PswCheck.SequenceEqual(_pswCheck))
+        {
+            throw new CryptographicException("The password did not match.");
+        }
+
+        var aes = Aes.Create();
+        aes.KeySize = AES_256;
+        aes.Mode = CipherMode.CBC;
+        aes.Padding = PaddingMode.None;
+        aes.Key = derivedKey[0];
+        aes.IV = _cryptoInfo.InitV;
+        return aes.CreateDecryptor();
+    }
+}

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

@@ -1,50 +1,19 @@
 #nullable disable
 
+using System;
+using System.Security.Cryptography;
+using SharpCompress.Common.Rar.Headers;
 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_PSWCHECK = 8;
-    private const int SIZE_PSWCHECK_CSUM = 4;
-    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) { }
 
-    protected override void ReadFinish(MarkingBinaryReader reader)
-    {
-        var cryptVersion = reader.ReadRarVIntUInt32();
-        if (cryptVersion > CRYPT_VERSION)
-        {
-            //error?
-            return;
-        }
-        var encryptionFlags = reader.ReadRarVIntUInt32();
-        _usePswCheck = FlagUtility.HasFlag(encryptionFlags, EncryptionFlagsV5.CHFL_CRYPT_PSWCHECK);
-        _lg2Count = reader.ReadRarVIntByte(1);
+    public Rar5CryptoInfo CryptInfo = new();
 
-        //UsePswCheck = HasHeaderFlag(EncryptionFlagsV5.CHFL_CRYPT_PSWCHECK);
-        if (_lg2Count > CRYPT5_KDF_LG2_COUNT_MAX)
-        {
-            //error?
-            return;
-        }
-
-        _salt = reader.ReadBytes(SIZE_SALT50);
-        if (_usePswCheck)
-        {
-            _pswCheck = reader.ReadBytes(SIZE_PSWCHECK);
-            _pswCheckCsm = reader.ReadBytes(SIZE_PSWCHECK_CSUM);
-        }
-    }
+    protected override void ReadFinish(MarkingBinaryReader reader) =>
+        CryptInfo = new Rar5CryptoInfo(reader, false);
 }

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

@@ -2,6 +2,8 @@
 
 using System;
 using System.IO;
+using System.Linq;
+using System.Security.Cryptography;
 using System.Text;
 using SharpCompress.IO;
 #if !Rar2017_64bit
@@ -16,7 +18,7 @@ namespace SharpCompress.Common.Rar.Headers;
 
 internal class FileHeader : RarHeader
 {
-    private uint _fileCrc;
+    private byte[] _hash;
 
     public FileHeader(RarHeader header, RarCrcBinaryReader reader, HeaderType headerType)
         : base(header, reader, headerType) { }
@@ -51,7 +53,7 @@ internal class FileHeader : RarHeader
 
         if (HasFlag(FileFlagsV5.HAS_CRC32))
         {
-            FileCrc = reader.ReadUInt32();
+            FileCrc = reader.ReadBytes(4);
         }
 
         var compressionInfo = reader.ReadRarVIntUInt16();
@@ -103,7 +105,13 @@ internal class FileHeader : RarHeader
             throw new InvalidFormatException("rar5 header size / extra size inconsistency");
         }
 
-        isEncryptedRar5 = false;
+        const ushort FHEXTRA_CRYPT = 0x01;
+        const ushort FHEXTRA_HASH = 0x02;
+        const ushort FHEXTRA_HTIME = 0x03;
+        // const ushort FHEXTRA_VERSION = 0x04;
+        const ushort FHEXTRA_REDIR = 0x05;
+        // const ushort FHEXTRA_UOWNER = 0x06;
+        // const ushort FHEXTRA_SUBDATA = 0x07;
 
         while (RemainingHeaderBytes(reader) > 0)
         {
@@ -112,23 +120,30 @@ internal class FileHeader : RarHeader
             var type = reader.ReadRarVIntUInt16();
             switch (type)
             {
-                //TODO
-                case 1: // file encryption
-
+                case FHEXTRA_CRYPT: // file encryption
                     {
-                        isEncryptedRar5 = true;
+                        Rar5CryptoInfo = new Rar5CryptoInfo(reader, true);
 
-                        //var version = reader.ReadRarVIntByte();
-                        //if (version != 0) throw new InvalidFormatException("unknown encryption algorithm " + version);
+                        if (Rar5CryptoInfo.PswCheck.All(singleByte => singleByte == 0))
+                        {
+                            Rar5CryptoInfo = null;
+                        }
                     }
                     break;
-                //                    case 2: // file hash
-                //                        {
-                //
-                //                        }
-                //                        break;
-                case 3: // file time
-
+                case FHEXTRA_HASH:
+                    {
+                        const uint FHEXTRA_HASH_BLAKE2 = 0x0;
+                        //                        const uint HASH_BLAKE2 = 0x03;
+                        const int BLAKE2_DIGEST_SIZE = 0x20;
+                        if ((uint)reader.ReadRarVInt() == FHEXTRA_HASH_BLAKE2)
+                        {
+                            //                            var hash = HASH_BLAKE2;
+                            _hash = reader.ReadBytes(BLAKE2_DIGEST_SIZE);
+                        }
+                        // enum HASH_TYPE {HASH_NONE,HASH_RAR14,HASH_CRC32,HASH_BLAKE2};
+                    }
+                    break;
+                case FHEXTRA_HTIME: // file time
                     {
                         var flags = reader.ReadRarVIntUInt16();
                         var isWindowsTime = (flags & 1) == 0;
@@ -147,22 +162,27 @@ internal class FileHeader : RarHeader
                     }
                     break;
                 //TODO
-                //                    case 4: // file version
+                //                    case FHEXTRA_VERSION: // file version
                 //                        {
                 //
                 //                        }
                 //                        break;
-                //                    case 5: // file system redirection
+                case FHEXTRA_REDIR: // file system redirection
+                    {
+                        RedirType = reader.ReadRarVIntByte();
+                        RedirFlags = reader.ReadRarVIntByte();
+                        var nn = reader.ReadRarVIntUInt16();
+                        var bb = reader.ReadBytes(nn);
+                        RedirTargetName = ConvertPathV5(Encoding.UTF8.GetString(bb, 0, bb.Length));
+                    }
+                    break;
+                //TODO
+                //                    case FHEXTRA_UOWNER: // unix owner
                 //                        {
                 //
                 //                        }
                 //                        break;
-                //                    case 6: // unix owner
-                //                        {
-                //
-                //                        }
-                //                        break;
-                //                    case 7: // service data
+                //                    case FHEXTRA_SUBDATA: // service data
                 //                        {
                 //
                 //                        }
@@ -170,6 +190,7 @@ internal class FileHeader : RarHeader
 
                 default:
                     // skip unknown record types to allow new record types to be added in the future
+                    //Console.WriteLine($"unhandled rar header field type {type}");
                     break;
             }
             // drain any trailing bytes of extra record
@@ -221,7 +242,7 @@ internal class FileHeader : RarHeader
 
         HostOs = reader.ReadByte();
 
-        FileCrc = reader.ReadUInt32();
+        FileCrc = reader.ReadBytes(4);
 
         FileLastModifiedTime = Utility.DosDateToDateTime(reader.ReadUInt32());
 
@@ -254,13 +275,11 @@ internal class FileHeader : RarHeader
 
         var fileNameBytes = reader.ReadBytes(nameSize);
 
-        const int saltSize = 8;
         const int newLhdSize = 32;
 
         switch (HeaderCode)
         {
             case HeaderCodeV.RAR4_FILE_HEADER:
-
                 {
                     if (HasFlag(FileFlagsV4.UNICODE))
                     {
@@ -287,12 +306,11 @@ internal class FileHeader : RarHeader
                 }
                 break;
             case HeaderCodeV.RAR4_NEW_SUB_HEADER:
-
                 {
                     var datasize = HeaderSize - newLhdSize - nameSize;
                     if (HasFlag(FileFlagsV4.SALT))
                     {
-                        datasize -= saltSize;
+                        datasize -= EncryptionConstV5.SIZE_SALT30;
                     }
                     if (datasize > 0)
                     {
@@ -313,7 +331,7 @@ internal class FileHeader : RarHeader
 
         if (HasFlag(FileFlagsV4.SALT))
         {
-            R4Salt = reader.ReadBytes(saltSize);
+            R4Salt = reader.ReadBytes(EncryptionConstV5.SIZE_SALT30);
         }
         if (HasFlag(FileFlagsV4.EXT_TIME))
         {
@@ -394,18 +412,10 @@ internal class FileHeader : RarHeader
 
     private bool HasFlag(ushort flag) => (Flags & flag) == flag;
 
-    internal uint FileCrc
+    internal byte[] FileCrc
     {
-        get
-        {
-            if (IsRar5 && !HasFlag(FileFlagsV5.HAS_CRC32))
-            {
-                //!!! rar5:
-                throw new InvalidOperationException("TODO rar5");
-            }
-            return _fileCrc;
-        }
-        private set => _fileCrc = value;
+        get => _hash;
+        private set => _hash = value;
     }
 
     // 0 - storing
@@ -427,11 +437,17 @@ internal class FileHeader : RarHeader
 
     public bool IsSolid { get; private set; }
 
+    public byte RedirType { get; private set; }
+    public bool IsRedir => RedirType != 0;
+    public byte RedirFlags { get; private set; }
+    public bool IsRedirDirectory => (RedirFlags & RedirFlagV5.DIRECTORY) != 0;
+    public string RedirTargetName { get; private set; }
+
     // unused for UnpackV1 implementation (limitation)
     internal size_t WindowSize { get; private set; }
 
     internal byte[] R4Salt { get; private set; }
-
+    internal Rar5CryptoInfo Rar5CryptoInfo { get; private set; }
     private byte HostOs { get; set; }
     internal uint FileAttributes { get; private set; }
     internal long CompressedSize { get; private set; }
@@ -449,8 +465,7 @@ internal class FileHeader : RarHeader
 
     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 ? Rar5CryptoInfo != null : HasFlag(FileFlagsV4.PASSWORD);
 
     internal DateTime? FileLastModifiedTime { get; private set; }
 

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

@@ -50,6 +50,17 @@ internal static class EncryptionFlagsV5
     public const uint FHEXTRA_CRYPT_HASHMAC = 0x02;
 }
 
+internal static class EncryptionConstV5
+{
+    public const int VERSION = 0;
+    public const uint CRYPT5_KDF_LG2_COUNT_MAX = 0x24;
+    public const int SIZE_SALT30 = 0x08;
+    public const int SIZE_SALT50 = 0x10;
+    public const int SIZE_INITV = 0x10;
+    public const int SIZE_PSWCHECK = 0x08;
+    public const int SIZE_PSWCHECK_CSUM = 0x04;
+}
+
 internal static class HeaderFlagsV5
 {
     public const ushort HAS_EXTRA = 0x0001;
@@ -146,3 +157,17 @@ internal static class EndArchiveFlagsV5
 {
     public const ushort HAS_NEXT_VOLUME = 0x0001;
 }
+
+internal static class RedirTypeV5
+{
+    public const byte UNIX_SYMLINK = 0x0001;
+    public const byte WIN_SYMLINK = 0x0002;
+    public const byte WIN_JUNCTION = 0x0003;
+    public const byte HARD_LINK = 0x0004;
+    public const byte FILE_COPY = 0x0005;
+}
+
+internal static class RedirFlagV5
+{
+    public const byte DIRECTORY = 0x0001;
+}

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

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.IO;
 using SharpCompress.IO;
 

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

@@ -1,5 +1,7 @@
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
+using SharpCompress.Common.Rar;
 using SharpCompress.IO;
 using SharpCompress.Readers;
 
@@ -9,6 +11,8 @@ public class RarHeaderFactory
 {
     private bool _isRar5;
 
+    private Rar5CryptoInfo? _cryptInfo;
+
     public RarHeaderFactory(StreamingMode mode, ReaderOptions options)
     {
         StreamingMode = mode;
@@ -53,7 +57,19 @@ public class RarHeaderFactory
                     "Encrypted Rar archive has no password specified."
                 );
             }
-            reader = new RarCryptoBinaryReader(stream, Options.Password);
+
+            if (_isRar5 && _cryptInfo != null)
+            {
+                _cryptInfo.ReadInitV(new MarkingBinaryReader(stream));
+                var _headerKey = new CryptKey5(Options.Password!, _cryptInfo);
+
+                reader = new RarCryptoBinaryReader(stream, _headerKey, _cryptInfo.Salt);
+            }
+            else
+            {
+                var key = new CryptKey3(Options.Password);
+                reader = new RarCryptoBinaryReader(stream, key);
+            }
         }
 
         var header = RarHeader.TryReadBase(reader, _isRar5, Options.ArchiveEncoding);
@@ -82,13 +98,11 @@ public class RarHeaderFactory
                 switch (StreamingMode)
                 {
                     case StreamingMode.Seekable:
-
                         {
                             reader.BaseStream.Position += ph.DataSize;
                         }
                         break;
                     case StreamingMode.Streaming:
-
                         {
                             reader.BaseStream.Skip(ph.DataSize);
                         }
@@ -105,7 +119,14 @@ public class RarHeaderFactory
             case HeaderCodeV.RAR5_SERVICE_HEADER:
             {
                 var fh = new FileHeader(header, reader, HeaderType.Service);
-                SkipData(fh, reader);
+                if (fh.FileName == "CMT")
+                {
+                    fh.PackedStream = new ReadOnlySubStream(reader.BaseStream, fh.CompressedSize);
+                }
+                else
+                {
+                    SkipData(fh, reader);
+                }
                 return fh;
             }
 
@@ -123,17 +144,15 @@ public class RarHeaderFactory
                 switch (StreamingMode)
                 {
                     case StreamingMode.Seekable:
-
                         {
                             fh.DataStartPosition = reader.BaseStream.Position;
                             reader.BaseStream.Position += fh.CompressedSize;
                         }
                         break;
                     case StreamingMode.Streaming:
-
                         {
                             var ms = new ReadOnlySubStream(reader.BaseStream, fh.CompressedSize);
-                            if (fh.R4Salt is null)
+                            if (fh.R4Salt is null && fh.Rar5CryptoInfo is null)
                             {
                                 fh.PackedStream = ms;
                             }
@@ -141,8 +160,10 @@ public class RarHeaderFactory
                             {
                                 fh.PackedStream = new RarCryptoWrapper(
                                     ms,
-                                    Options.Password!,
-                                    fh.R4Salt
+                                    fh.R4Salt is null ? fh.Rar5CryptoInfo.Salt : fh.R4Salt,
+                                    fh.R4Salt is null
+                                        ? new CryptKey5(Options.Password!, fh.Rar5CryptoInfo)
+                                        : new CryptKey3(Options.Password!)
                                 );
                             }
                         }
@@ -161,9 +182,11 @@ public class RarHeaderFactory
             }
             case HeaderCodeV.RAR5_ARCHIVE_ENCRYPTION_HEADER:
             {
-                var ch = new ArchiveCryptHeader(header, reader);
+                var cryptoHeader = new ArchiveCryptHeader(header, reader);
                 IsEncrypted = true;
-                return ch;
+                _cryptInfo = cryptoHeader.CryptInfo;
+
+                return cryptoHeader;
             }
             default:
             {
@@ -177,14 +200,12 @@ public class RarHeaderFactory
         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);

src/SharpCompress/Common/Rar/ICryptKey.cs

@@ -0,0 +1,8 @@
+using System.Security.Cryptography;
+
+namespace SharpCompress.Common.Rar;
+
+internal interface ICryptKey
+{
+    ICryptoTransform Transformer(byte[] salt);
+}

src/SharpCompress/Common/Rar/Rar5CryptoInfo.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Security.Cryptography;
+using SharpCompress.Common.Rar.Headers;
+using SharpCompress.IO;
+
+namespace SharpCompress.Common.Rar;
+
+internal class Rar5CryptoInfo
+{
+    public Rar5CryptoInfo() { }
+
+    public Rar5CryptoInfo(MarkingBinaryReader reader, bool readInitV)
+    {
+        var cryptVersion = reader.ReadRarVIntUInt32();
+        if (cryptVersion > EncryptionConstV5.VERSION)
+        {
+            throw new CryptographicException($"Unsupported crypto version of {cryptVersion}");
+        }
+        var encryptionFlags = reader.ReadRarVIntUInt32();
+        UsePswCheck = FlagUtility.HasFlag(encryptionFlags, EncryptionFlagsV5.CHFL_CRYPT_PSWCHECK);
+        LG2Count = reader.ReadRarVIntByte(1);
+
+        if (LG2Count > EncryptionConstV5.CRYPT5_KDF_LG2_COUNT_MAX)
+        {
+            throw new CryptographicException($"Unsupported LG2 count of {LG2Count}.");
+        }
+
+        Salt = reader.ReadBytes(EncryptionConstV5.SIZE_SALT50);
+
+        if (readInitV) // File header needs to read IV here
+        {
+            ReadInitV(reader);
+        }
+
+        if (UsePswCheck)
+        {
+            PswCheck = reader.ReadBytes(EncryptionConstV5.SIZE_PSWCHECK);
+            var _pswCheckCsm = reader.ReadBytes(EncryptionConstV5.SIZE_PSWCHECK_CSUM);
+
+            var sha = SHA256.Create();
+            UsePswCheck = sha.ComputeHash(PswCheck).AsSpan().StartsWith(_pswCheckCsm.AsSpan());
+        }
+    }
+
+    public void ReadInitV(MarkingBinaryReader reader) =>
+        InitV = reader.ReadBytes(EncryptionConstV5.SIZE_INITV);
+
+    public bool UsePswCheck = false;
+
+    public int LG2Count = 0;
+
+    public byte[] InitV = { };
+
+    public byte[] Salt = { };
+
+    public byte[] PswCheck = { };
+}

src/SharpCompress/Common/Rar/RarCryptoBinaryReader.cs

@@ -1,29 +1,29 @@
-using System.Collections.Generic;
+#nullable disable
+
+using System.Collections.Generic;
 using System.IO;
+using SharpCompress.Common.Rar.Headers;
+using SharpCompress.Crypto;
 
 namespace SharpCompress.Common.Rar;
 
 internal sealed class RarCryptoBinaryReader : RarCrcBinaryReader
 {
-    private RarRijndael _rijndael;
-    private byte[] _salt;
-    private readonly string _password;
-    private readonly Queue<byte> _data = new Queue<byte>();
+    private BlockTransformer _rijndael;
+    private readonly Queue<byte> _data = new();
     private long _readCount;
 
-    public RarCryptoBinaryReader(Stream stream, string password)
+    public RarCryptoBinaryReader(Stream stream, ICryptKey cryptKey)
         : base(stream)
     {
-        _password = password;
-
-        // coderb: not sure why this was being done at this logical point
-        //SkipQueue();
-        var salt = ReadBytes(8);
-
-        _salt = salt;
-        _rijndael = RarRijndael.InitializeFrom(_password, salt);
+        var salt = base.ReadBytes(EncryptionConstV5.SIZE_SALT30);
+        _readCount += EncryptionConstV5.SIZE_SALT30;
+        _rijndael = new BlockTransformer(cryptKey.Transformer(salt));
     }
 
+    public RarCryptoBinaryReader(Stream stream, ICryptKey cryptKey, byte[] salt)
+        : base(stream) => _rijndael = new BlockTransformer(cryptKey.Transformer(salt));
+
     // track read count ourselves rather than using the underlying stream since we buffer
     public override long CurrentReadByteCount
     {
@@ -36,29 +36,9 @@ internal sealed class RarCryptoBinaryReader : RarCrcBinaryReader
 
     public override void Mark() => _readCount = 0;
 
-    private bool UseEncryption => _salt != null;
+    public override byte ReadByte() => ReadAndDecryptBytes(1)[0];
 
-    public override byte ReadByte()
-    {
-        if (UseEncryption)
-        {
-            return ReadAndDecryptBytes(1)[0];
-        }
-
-        _readCount++;
-        return base.ReadByte();
-    }
-
-    public override byte[] ReadBytes(int count)
-    {
-        if (UseEncryption)
-        {
-            return ReadAndDecryptBytes(count);
-        }
-
-        _readCount += count;
-        return base.ReadBytes(count);
-    }
+    public override byte[] ReadBytes(int count) => ReadAndDecryptBytes(count);
 
     private byte[] ReadAndDecryptBytes(int count)
     {

src/SharpCompress/Common/Rar/RarCryptoWrapper.cs

@@ -1,37 +1,30 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using SharpCompress.Crypto;
 
 namespace SharpCompress.Common.Rar;
 
 internal sealed class RarCryptoWrapper : Stream
 {
     private readonly Stream _actualStream;
-    private readonly byte[] _salt;
-    private RarRijndael _rijndael;
-    private readonly Queue<byte> _data = new Queue<byte>();
+    private BlockTransformer _rijndael;
+    private readonly Queue<byte> _data = new();
 
-    public RarCryptoWrapper(Stream actualStream, string password, byte[] salt)
+    public RarCryptoWrapper(Stream actualStream, byte[] salt, ICryptKey key)
     {
         _actualStream = actualStream;
-        _salt = salt;
-        _rijndael = RarRijndael.InitializeFrom(password ?? "", salt);
+        _rijndael = new BlockTransformer(key.Transformer(salt));
     }
 
-    public override void Flush() => throw new NotSupportedException();
+    public override void Flush() { }
 
     public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
 
     public override void SetLength(long value) => throw new NotSupportedException();
 
-    public override int Read(byte[] buffer, int offset, int count)
-    {
-        if (_salt is null)
-        {
-            return _actualStream.Read(buffer, offset, count);
-        }
-        return ReadAndDecrypt(buffer, offset, count);
-    }
+    public override int Read(byte[] buffer, int offset, int count) =>
+        ReadAndDecrypt(buffer, offset, count);
 
     public int ReadAndDecrypt(byte[] buffer, int offset, int count)
     {
@@ -41,7 +34,7 @@ internal sealed class RarCryptoWrapper : Stream
         if (sizeToRead > 0)
         {
             var alignedSize = sizeToRead + ((~sizeToRead + 1) & 0xf);
-            Span<byte> cipherText = stackalloc byte[RarRijndael.CRYPTO_BLOCK_SIZE];
+            Span<byte> cipherText = stackalloc byte[16];
             for (var i = 0; i < alignedSize / 16; i++)
             {
                 //long ax = System.currentTimeMillis();
@@ -77,11 +70,11 @@ internal sealed class RarCryptoWrapper : Stream
 
     protected override void Dispose(bool disposing)
     {
-        if (_rijndael != null)
+        if (disposing)
         {
             _rijndael.Dispose();
-            _rijndael = null!;
         }
+
         base.Dispose(disposing);
     }
 }

src/SharpCompress/Common/Rar/RarEntry.cs

@@ -20,12 +20,12 @@ public abstract class RarEntry : Entry
     /// <summary>
     /// The File's 32 bit CRC Hash
     /// </summary>
-    public override long Crc => FileHeader.FileCrc;
+    public override long Crc => BitConverter.ToUInt32(FileHeader.FileCrc, 0);
 
     /// <summary>
     /// The path of the file internal to the Rar Archive.
     /// </summary>
-    public override string Key => FileHeader.FileName;
+    public override string? Key => FileHeader.FileName;
 
     public override string? LinkTarget => null;
 
@@ -55,12 +55,21 @@ public abstract class RarEntry : Entry
     public override bool IsEncrypted => FileHeader.IsEncrypted;
 
     /// <summary>
-    /// Entry is password protected and encrypted and cannot be extracted.
+    /// Entry Windows file attributes
+    /// </summary>
+    public override int? Attrib => (int)FileHeader.FileAttributes;
+
+    /// <summary>
+    /// Entry is a directory
     /// </summary>
     public override bool IsDirectory => FileHeader.IsDirectory;
 
     public override bool IsSplitAfter => FileHeader.IsSplitAfter;
 
+    public bool IsRedir => FileHeader.IsRedir;
+
+    public string RedirTargetName => FileHeader.RedirTargetName;
+
     public override string ToString() =>
         string.Format(
             "Entry Path: {0} Compressed Size: {1} Uncompressed Size: {2} CRC: {3}",

src/SharpCompress/Common/Rar/RarRijndael.cs

@@ -1,114 +0,0 @@
-#nullable disable
-
-using System;
-using System.Security.Cryptography;
-using System.Text;
-using SharpCompress.Crypto;
-
-namespace SharpCompress.Common.Rar;
-
-internal class RarRijndael : IDisposable
-{
-    internal const int CRYPTO_BLOCK_SIZE = 16;
-
-    private readonly string _password;
-    private readonly byte[] _salt;
-    private byte[] _aesInitializationVector;
-    private RijndaelEngine _rijndael;
-
-    private RarRijndael(string password, byte[] salt)
-    {
-        _password = password;
-        _salt = salt;
-    }
-
-    private void Initialize()
-    {
-        _rijndael = new RijndaelEngine();
-        _aesInitializationVector = new byte[CRYPTO_BLOCK_SIZE];
-        var rawLength = 2 * _password.Length;
-        var rawPassword = new byte[rawLength + 8];
-        var passwordBytes = Encoding.UTF8.GetBytes(_password);
-        for (var i = 0; i < _password.Length; i++)
-        {
-            rawPassword[i * 2] = passwordBytes[i];
-            rawPassword[(i * 2) + 1] = 0;
-        }
-        for (var i = 0; i < _salt.Length; i++)
-        {
-            rawPassword[i + rawLength] = _salt[i];
-        }
-
-        const int noOfRounds = (1 << 18);
-        const int iblock = 3;
-        byte[] digest;
-        var data = new byte[(rawPassword.Length + iblock) * noOfRounds];
-
-        //TODO slow code below, find ways to optimize
-        for (var i = 0; i < noOfRounds; i++)
-        {
-            rawPassword.CopyTo(data, i * (rawPassword.Length + iblock));
-
-            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 0] = (byte)i;
-            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 1] = (byte)(i >> 8);
-            data[(i * (rawPassword.Length + iblock)) + rawPassword.Length + 2] = (byte)(
-                i >> CRYPTO_BLOCK_SIZE
-            );
-
-            if (i % (noOfRounds / CRYPTO_BLOCK_SIZE) == 0)
-            {
-                digest = SHA1.Create()
-                    .ComputeHash(data, 0, (i + 1) * (rawPassword.Length + iblock));
-                _aesInitializationVector[i / (noOfRounds / CRYPTO_BLOCK_SIZE)] = digest[19];
-            }
-        }
-        digest = SHA1.Create().ComputeHash(data);
-        //slow code ends
-
-        var aesKey = new byte[CRYPTO_BLOCK_SIZE];
-        for (var i = 0; i < 4; i++)
-        {
-            for (var 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)
-                );
-            }
-        }
-
-        _rijndael.Init(false, new KeyParameter(aesKey));
-    }
-
-    public static RarRijndael InitializeFrom(string password, byte[] salt)
-    {
-        var rijndael = new RarRijndael(password, salt);
-        rijndael.Initialize();
-        return rijndael;
-    }
-
-    public byte[] ProcessBlock(ReadOnlySpan<byte> cipherText)
-    {
-        Span<byte> plainText = stackalloc byte[CRYPTO_BLOCK_SIZE]; // 16 bytes
-        var decryptedBytes = new byte[CRYPTO_BLOCK_SIZE];
-        _rijndael.ProcessBlock(cipherText, plainText);
-
-        for (var j = 0; j < CRYPTO_BLOCK_SIZE; j++)
-        {
-            decryptedBytes[j] = (byte)(plainText[j] ^ _aesInitializationVector[j % 16]); //32:114, 33:101
-        }
-
-        for (var j = 0; j < _aesInitializationVector.Length; j++)
-        {
-            _aesInitializationVector[j] = cipherText[j];
-        }
-
-        return decryptedBytes;
-    }
-
-    public void Dispose() { }
-}

src/SharpCompress/Common/Rar/RarVolume.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Text;
 using SharpCompress.Common.Rar.Headers;
 using SharpCompress.IO;
 using SharpCompress.Readers;
@@ -14,17 +15,14 @@ namespace SharpCompress.Common.Rar;
 public abstract class RarVolume : Volume
 {
     private readonly RarHeaderFactory _headerFactory;
-    internal int _maxCompressionAlgorithm;
+    private int _maxCompressionAlgorithm;
 
-    internal RarVolume(StreamingMode mode, Stream stream, ReaderOptions options, int index = 0)
+    internal RarVolume(StreamingMode mode, Stream stream, ReaderOptions options, int index)
         : base(stream, options, index) => _headerFactory = new RarHeaderFactory(mode, options);
 
-#nullable disable
-    internal ArchiveHeader ArchiveHeader { get; private set; }
+    private ArchiveHeader? ArchiveHeader { get; set; }
 
-#nullable enable
-
-    internal StreamingMode Mode => _headerFactory.StreamingMode;
+    private StreamingMode Mode => _headerFactory.StreamingMode;
 
     internal abstract IEnumerable<RarFilePart> ReadFileParts();
 
@@ -38,19 +36,16 @@ public abstract class RarVolume : Volume
             switch (header.HeaderType)
             {
                 case HeaderType.Mark:
-
                     {
                         lastMarkHeader = (MarkHeader)header;
                     }
                     break;
                 case HeaderType.Archive:
-
                     {
                         ArchiveHeader = (ArchiveHeader)header;
                     }
                     break;
                 case HeaderType.File:
-
                     {
                         var fh = (FileHeader)header;
                         if (_maxCompressionAlgorithm < fh.CompressionAlgorithm)
@@ -62,7 +57,6 @@ public abstract class RarVolume : Volume
                     }
                     break;
                 case HeaderType.Service:
-
                     {
                         var fh = (FileHeader)header;
                         if (fh.FileName == "CMT")
@@ -70,11 +64,7 @@ public abstract class RarVolume : Volume
                             var part = CreateFilePart(lastMarkHeader!, fh);
                             var buffer = new byte[fh.CompressedSize];
                             part.GetCompressedStream().Read(buffer, 0, buffer.Length);
-                            Comment = System
-                                .Text
-                                .Encoding
-                                .UTF8
-                                .GetString(buffer, 0, buffer.Length - 1);
+                            Comment = Encoding.UTF8.GetString(buffer, 0, buffer.Length - 1);
                         }
                     }
                     break;
@@ -108,7 +98,7 @@ public abstract class RarVolume : Volume
         get
         {
             EnsureArchiveHeaderLoaded();
-            return ArchiveHeader.IsFirstVolume;
+            return ArchiveHeader?.IsFirstVolume ?? false;
         }
     }
 
@@ -120,7 +110,7 @@ public abstract class RarVolume : Volume
         get
         {
             EnsureArchiveHeaderLoaded();
-            return ArchiveHeader.IsVolume;
+            return ArchiveHeader?.IsVolume ?? false;
         }
     }
 
@@ -133,7 +123,7 @@ public abstract class RarVolume : Volume
         get
         {
             EnsureArchiveHeaderLoaded();
-            return ArchiveHeader.IsSolid;
+            return ArchiveHeader?.IsSolid ?? false;
         }
     }
 

src/SharpCompress/Common/SevenZip/ArchiveDatabase.cs

@@ -15,15 +15,15 @@ internal class ArchiveDatabase
     internal long _startPositionAfterHeader;
     internal long _dataStartPosition;
 
-    internal List<long> _packSizes = new List<long>();
-    internal List<uint?> _packCrCs = new List<uint?>();
-    internal List<CFolder> _folders = new List<CFolder>();
+    internal List<long> _packSizes = new();
+    internal List<uint?> _packCrCs = new();
+    internal List<CFolder> _folders = new();
     internal List<int> _numUnpackStreamsVector;
-    internal List<CFileItem> _files = new List<CFileItem>();
+    internal List<CFileItem> _files = new();
 
-    internal List<long> _packStreamStartPositions = new List<long>();
-    internal List<int> _folderStartFileIndex = new List<int>();
-    internal List<int> _fileIndexToFolderIndexMap = new List<int>();
+    internal List<long> _packStreamStartPositions = new();
+    internal List<int> _folderStartFileIndex = new();
+    internal List<int> _fileIndexToFolderIndexMap = new();
 
     internal IPasswordProvider PasswordProvider { get; }
 
@@ -35,7 +35,7 @@ internal class ArchiveDatabase
         _packSizes.Clear();
         _packCrCs.Clear();
         _folders.Clear();
-        _numUnpackStreamsVector = null!;
+        _numUnpackStreamsVector = null;
         _files.Clear();
 
         _packStreamStartPositions.Clear();

src/SharpCompress/Common/SevenZip/ArchiveReader.cs

@@ -14,13 +14,13 @@ namespace SharpCompress.Common.SevenZip;
 internal class ArchiveReader
 {
     internal Stream _stream;
-    internal Stack<DataReader> _readerStack = new Stack<DataReader>();
+    internal Stack<DataReader> _readerStack = new();
     internal DataReader _currentReader;
     internal long _streamOrigin;
     internal long _streamEnding;
     internal byte[] _header;
 
-    private readonly Dictionary<int, Stream> _cachedStreams = new Dictionary<int, Stream>();
+    private readonly Dictionary<int, Stream> _cachedStreams = new();
 
     internal void AddByteStream(byte[] buffer, int offset, int length)
     {
@@ -1359,7 +1359,7 @@ internal class ArchiveReader
     {
         internal int _fileIndex;
         internal int _folderIndex;
-        internal List<bool> _extractStatuses = new List<bool>();
+        internal List<bool> _extractStatuses = new();
 
         internal CExtractFolderInfo(int fileIndex, int folderIndex)
         {
@@ -1393,7 +1393,7 @@ internal class ArchiveReader
 
         public override bool CanWrite => false;
 
-        public override void Flush() => throw new NotSupportedException();
+        public override void Flush() { }
 
         public override long Length => throw new NotSupportedException();
 

src/SharpCompress/Common/SevenZip/CFolder.cs

@@ -6,11 +6,11 @@ namespace SharpCompress.Common.SevenZip;
 
 internal class CFolder
 {
-    internal List<CCoderInfo> _coders = new List<CCoderInfo>();
-    internal List<CBindPair> _bindPairs = new List<CBindPair>();
-    internal List<int> _packStreams = new List<int>();
+    internal List<CCoderInfo> _coders = new();
+    internal List<CBindPair> _bindPairs = new();
+    internal List<int> _packStreams = new();
     internal int _firstPackStreamId;
-    internal List<long> _unpackSizes = new List<long>();
+    internal List<long> _unpackSizes = new();
     internal uint? _unpackCrc;
 
     internal bool UnpackCrcDefined => _unpackCrc != null;

src/SharpCompress/Common/SevenZip/CMethodId.cs

@@ -7,10 +7,10 @@ internal readonly struct CMethodId
     public const ulong K_LZMA2_ID = 0x21;
     public const ulong K_AES_ID = 0x06F10701;
 
-    public static readonly CMethodId K_COPY = new CMethodId(K_COPY_ID);
-    public static readonly CMethodId K_LZMA = new CMethodId(K_LZMA_ID);
-    public static readonly CMethodId K_LZMA2 = new CMethodId(K_LZMA2_ID);
-    public static readonly CMethodId K_AES = new CMethodId(K_AES_ID);
+    public static readonly CMethodId K_COPY = new(K_COPY_ID);
+    public static readonly CMethodId K_LZMA = new(K_LZMA_ID);
+    public static readonly CMethodId K_LZMA2 = new(K_LZMA2_ID);
+    public static readonly CMethodId K_AES = new(K_AES_ID);
 
     public readonly ulong _id;
 

src/SharpCompress/Common/SevenZip/SevenZipEntry.cs

@@ -13,7 +13,7 @@ public class SevenZipEntry : Entry
 
     public override long Crc => FilePart.Header.Crc ?? 0;
 
-    public override string Key => FilePart.Header.Name;
+    public override string? Key => FilePart.Header.Name;
 
     public override string? LinkTarget => null;
 

src/SharpCompress/Common/SevenZip/SevenZipFilePart.cs

@@ -41,7 +41,7 @@ internal class SevenZipFilePart : FilePart
     {
         if (!Header.HasStream)
         {
-            return null!;
+            throw new InvalidOperationException("File does not have a stream.");
         }
         var folderStream = _database.GetFolderStream(_stream, Folder!, _database.PasswordProvider);
 
@@ -73,34 +73,24 @@ internal class SevenZipFilePart : FilePart
     private const uint K_PPMD = 0x030401;
     private const uint K_B_ZIP2 = 0x040202;
 
-    internal CompressionType GetCompression()
+    private CompressionType GetCompression()
     {
         if (Header.IsDir)
-            return CompressionType.None;
-
-        var coder = Folder!._coders.First();
-        switch (coder._methodId._id)
         {
-            case K_LZMA:
-            case K_LZMA2:
-            {
-                return CompressionType.LZMA;
-            }
-            case K_PPMD:
-            {
-                return CompressionType.PPMd;
-            }
-            case K_B_ZIP2:
-            {
-                return CompressionType.BZip2;
-            }
-            default:
-                throw new NotImplementedException();
+            return CompressionType.None;
         }
+
+        var coder = Folder.NotNull()._coders.First();
+        return coder._methodId._id switch
+        {
+            K_LZMA or K_LZMA2 => CompressionType.LZMA,
+            K_PPMD => CompressionType.PPMd,
+            K_B_ZIP2 => CompressionType.BZip2,
+            _ => throw new NotImplementedException()
+        };
     }
 
     internal bool IsEncrypted =>
-        Header.IsDir
-            ? false
-            : Folder!._coders.FindIndex(c => c._methodId._id == CMethodId.K_AES_ID) != -1;
+        !Header.IsDir
+        && Folder?._coders.FindIndex(c => c._methodId._id == CMethodId.K_AES_ID) != -1;
 }

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

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Buffers.Binary;
 using System.IO;
@@ -9,12 +7,12 @@ namespace SharpCompress.Common.Tar.Headers;
 
 internal sealed class TarHeader
 {
-    internal static readonly DateTime EPOCH = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+    internal static readonly DateTime EPOCH = new(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
 
     public TarHeader(ArchiveEncoding archiveEncoding) => ArchiveEncoding = archiveEncoding;
 
-    internal string Name { get; set; }
-    internal string LinkName { get; set; }
+    internal string? Name { get; set; }
+    internal string? LinkName { get; set; }
 
     internal long Mode { get; set; }
     internal long UserId { get; set; }
@@ -22,7 +20,7 @@ internal sealed class TarHeader
     internal long Size { get; set; }
     internal DateTime LastModifiedTime { get; set; }
     internal EntryType EntryType { get; set; }
-    internal Stream PackedStream { get; set; }
+    internal Stream? PackedStream { get; set; }
     internal ArchiveEncoding ArchiveEncoding { get; }
 
     internal const int BLOCK_SIZE = 512;
@@ -36,7 +34,9 @@ internal sealed class TarHeader
         WriteOctalBytes(0, buffer, 116, 8); // group ID
 
         //ArchiveEncoding.UTF8.GetBytes("magic").CopyTo(buffer, 257);
-        var nameByteCount = ArchiveEncoding.GetEncoding().GetByteCount(Name);
+        var nameByteCount = ArchiveEncoding
+            .GetEncoding()
+            .GetByteCount(Name.NotNull("Name is null"));
         if (nameByteCount > 100)
         {
             // Set mock filename and filetype to indicate the next block is the actual name of the file
@@ -46,7 +46,7 @@ internal sealed class TarHeader
         }
         else
         {
-            WriteStringBytes(ArchiveEncoding.Encode(Name), buffer, 100);
+            WriteStringBytes(ArchiveEncoding.Encode(Name.NotNull("Name is null")), buffer, 100);
             WriteOctalBytes(Size, buffer, 124, 12);
             var time = (long)(LastModifiedTime.ToUniversalTime() - EPOCH).TotalSeconds;
             WriteOctalBytes(time, buffer, 136, 12);
@@ -77,7 +77,7 @@ internal sealed class TarHeader
             //
             // and then infinite recursion is occured in WriteLongFilenameHeader because truncated.Length is 102.
             Name = ArchiveEncoding.Decode(
-                ArchiveEncoding.Encode(Name),
+                ArchiveEncoding.Encode(Name.NotNull("Name is null")),
                 0,
                 100 - ArchiveEncoding.GetEncoding().GetMaxByteCount(1)
             );
@@ -87,7 +87,7 @@ internal sealed class TarHeader
 
     private void WriteLongFilenameHeader(Stream output)
     {
-        var nameBytes = ArchiveEncoding.Encode(Name);
+        var nameBytes = ArchiveEncoding.Encode(Name.NotNull("Name is null"));
         output.Write(nameBytes, 0, nameBytes.Length);
 
         // pad to multiple of BlockSize bytes, and make sure a terminating null is added
@@ -132,8 +132,8 @@ internal sealed class TarHeader
             Mode |= 0b1_000_000_000;
         }
 
-        UserId = ReadAsciiInt64Base8(buffer, 108, 7);
-        GroupId = ReadAsciiInt64Base8(buffer, 116, 7);
+        UserId = ReadAsciiInt64Base8oldGnu(buffer, 108, 7);
+        GroupId = ReadAsciiInt64Base8oldGnu(buffer, 116, 7);
         var unixTimeStamp = ReadAsciiInt64Base8(buffer, 136, 11);
         LastModifiedTime = EPOCH.AddSeconds(unixTimeStamp).ToLocalTime();
 
@@ -249,6 +249,24 @@ internal sealed class TarHeader
         return Convert.ToInt64(s, 8);
     }
 
+    private static long ReadAsciiInt64Base8oldGnu(byte[] buffer, int offset, int count)
+    {
+        if (buffer[offset] == 0x80 && buffer[offset + 1] == 0x00)
+        {
+            return buffer[offset + 4] << 24
+                | buffer[offset + 5] << 16
+                | buffer[offset + 6] << 8
+                | buffer[offset + 7];
+        }
+        var s = Encoding.UTF8.GetString(buffer, offset, count).TrimNulls();
+
+        if (string.IsNullOrEmpty(s))
+        {
+            return 0;
+        }
+        return Convert.ToInt64(s, 8);
+    }
+
     private static long ReadAsciiInt64(byte[] buffer, int offset, int count)
     {
         var s = Encoding.UTF8.GetString(buffer, offset, count).TrimNulls();
@@ -305,5 +323,5 @@ internal sealed class TarHeader
 
     public long? DataStartPosition { get; set; }
 
-    public string Magic { get; set; }
+    public string? Magic { get; set; }
 }

src/SharpCompress/Common/Tar/TarEntry.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.IO;
@@ -10,9 +8,9 @@ namespace SharpCompress.Common.Tar;
 
 public class TarEntry : Entry
 {
-    private readonly TarFilePart _filePart;
+    private readonly TarFilePart? _filePart;
 
-    internal TarEntry(TarFilePart filePart, CompressionType type)
+    internal TarEntry(TarFilePart? filePart, CompressionType type)
     {
         _filePart = filePart;
         CompressionType = type;
@@ -22,15 +20,15 @@ public class TarEntry : Entry
 
     public override long Crc => 0;
 
-    public override string Key => _filePart.Header.Name;
+    public override string? Key => _filePart?.Header.Name;
 
-    public override string LinkTarget => _filePart.Header.LinkName;
+    public override string? LinkTarget => _filePart?.Header.LinkName;
 
-    public override long CompressedSize => _filePart.Header.Size;
+    public override long CompressedSize => _filePart?.Header.Size ?? 0;
 
-    public override long Size => _filePart.Header.Size;
+    public override long Size => _filePart?.Header.Size ?? 0;
 
-    public override DateTime? LastModifiedTime => _filePart.Header.LastModifiedTime;
+    public override DateTime? LastModifiedTime => _filePart?.Header.LastModifiedTime;
 
     public override DateTime? CreatedTime => null;
 
@@ -40,17 +38,17 @@ public class TarEntry : Entry
 
     public override bool IsEncrypted => false;
 
-    public override bool IsDirectory => _filePart.Header.EntryType == EntryType.Directory;
+    public override bool IsDirectory => _filePart?.Header.EntryType == EntryType.Directory;
 
     public override bool IsSplitAfter => false;
 
-    public long Mode => _filePart.Header.Mode;
+    public long Mode => _filePart?.Header.Mode ?? 0;
 
-    public long UserID => _filePart.Header.UserId;
+    public long UserID => _filePart?.Header.UserId ?? 0;
 
-    public long GroupId => _filePart.Header.GroupId;
+    public long GroupId => _filePart?.Header.GroupId ?? 0;
 
-    internal override IEnumerable<FilePart> Parts => _filePart.AsEnumerable<FilePart>();
+    internal override IEnumerable<FilePart> Parts => _filePart.Empty();
 
     internal static IEnumerable<TarEntry> GetEntries(
         StreamingMode mode,
@@ -59,17 +57,17 @@ public class TarEntry : Entry
         ArchiveEncoding archiveEncoding
     )
     {
-        foreach (var h in TarHeaderFactory.ReadHeader(mode, stream, archiveEncoding))
+        foreach (var header in TarHeaderFactory.ReadHeader(mode, stream, archiveEncoding))
         {
-            if (h != null)
+            if (header != null)
             {
                 if (mode == StreamingMode.Seekable)
                 {
-                    yield return new TarEntry(new TarFilePart(h, stream), compressionType);
+                    yield return new TarEntry(new TarFilePart(header, stream), compressionType);
                 }
                 else
                 {
-                    yield return new TarEntry(new TarFilePart(h, null), compressionType);
+                    yield return new TarEntry(new TarFilePart(header, null), compressionType);
                 }
             }
             else

src/SharpCompress/Common/Tar/TarFilePart.cs

@@ -5,9 +5,9 @@ namespace SharpCompress.Common.Tar;
 
 internal sealed class TarFilePart : FilePart
 {
-    private readonly Stream _seekableStream;
+    private readonly Stream? _seekableStream;
 
-    internal TarFilePart(TarHeader header, Stream seekableStream)
+    internal TarFilePart(TarHeader header, Stream? seekableStream)
         : base(header.ArchiveEncoding)
     {
         _seekableStream = seekableStream;
@@ -16,16 +16,16 @@ internal sealed class TarFilePart : FilePart
 
     internal TarHeader Header { get; }
 
-    internal override string FilePartName => Header.Name;
+    internal override string? FilePartName => Header?.Name;
 
     internal override Stream GetCompressedStream()
     {
         if (_seekableStream != null)
         {
-            _seekableStream.Position = Header.DataStartPosition!.Value;
+            _seekableStream.Position = Header.DataStartPosition ?? 0;
             return new TarReadOnlySubStream(_seekableStream, Header.Size);
         }
-        return Header.PackedStream;
+        return Header.PackedStream.NotNull();
     }
 
     internal override Stream? GetRawStream() => null;

src/SharpCompress/Common/Tar/TarHeaderFactory.cs

@@ -28,7 +28,6 @@ internal static class TarHeaderFactory
                 switch (mode)
                 {
                     case StreamingMode.Seekable:
-
                         {
                             header.DataStartPosition = reader.BaseStream.Position;
 
@@ -37,7 +36,6 @@ internal static class TarHeaderFactory
                         }
                         break;
                     case StreamingMode.Streaming:
-
                         {
                             header.PackedStream = new TarReadOnlySubStream(stream, header.Size);
                         }

src/SharpCompress/Common/Tar/TarReadOnlySubStream.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.IO;
 using SharpCompress.IO;
 
@@ -47,7 +47,7 @@ internal class TarReadOnlySubStream : NonDisposingStream
 
     public override bool CanWrite => false;
 
-    public override void Flush() => throw new NotSupportedException();
+    public override void Flush() { }
 
     public override long Length => throw new NotSupportedException();
 
@@ -63,7 +63,7 @@ internal class TarReadOnlySubStream : NonDisposingStream
         {
             count = (int)BytesLeftToRead;
         }
-        int read = Stream.Read(buffer, offset, count);
+        var read = Stream.Read(buffer, offset, count);
         if (read > 0)
         {
             BytesLeftToRead -= read;
@@ -78,7 +78,7 @@ internal class TarReadOnlySubStream : NonDisposingStream
         {
             return -1;
         }
-        int value = Stream.ReadByte();
+        var value = Stream.ReadByte();
         if (value != -1)
         {
             --BytesLeftToRead;

src/SharpCompress/Common/Volume.cs

@@ -9,11 +9,11 @@ public abstract class Volume : IVolume
 {
     private readonly Stream _actualStream;
 
-    internal Volume(Stream stream, ReaderOptions readerOptions, int index = 0)
+    internal Volume(Stream stream, ReaderOptions? readerOptions, int index = 0)
     {
         Index = index;
-        ReaderOptions = readerOptions;
-        if (readerOptions.LeaveStreamOpen)
+        ReaderOptions = readerOptions ?? new ReaderOptions();
+        if (ReaderOptions.LeaveStreamOpen)
         {
             stream = NonDisposingStream.Create(stream);
         }
@@ -32,7 +32,7 @@ public abstract class Volume : IVolume
 
     public virtual int Index { get; internal set; }
 
-    public string FileName => (_actualStream as FileStream)?.Name!;
+    public string? FileName => (_actualStream as FileStream)?.Name;
 
     /// <summary>
     /// RarArchive is part of a multi-part archive.

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

@@ -14,8 +14,8 @@ internal class DirectoryEntryHeader : ZipFileEntry
         VersionNeededToExtract = reader.ReadUInt16();
         Flags = (HeaderFlags)reader.ReadUInt16();
         CompressionMethod = (ZipCompressionMethod)reader.ReadUInt16();
-        LastModifiedTime = reader.ReadUInt16();
-        LastModifiedDate = reader.ReadUInt16();
+        OriginalLastModifiedTime = LastModifiedTime = reader.ReadUInt16();
+        OriginalLastModifiedDate = LastModifiedDate = reader.ReadUInt16();
         Crc = reader.ReadUInt32();
         CompressedSize = reader.ReadUInt32();
         UncompressedSize = reader.ReadUInt32();
@@ -52,8 +52,8 @@ internal class DirectoryEntryHeader : ZipFileEntry
 
         LoadExtra(extra);
 
-        var unicodePathExtra = Extra.FirstOrDefault(
-            u => u.Type == ExtraDataType.UnicodePathExtraField
+        var unicodePathExtra = Extra.FirstOrDefault(u =>
+            u.Type == ExtraDataType.UnicodePathExtraField
         );
         if (unicodePathExtra != null && ArchiveEncoding.Forced == null)
         {
@@ -85,6 +85,36 @@ internal class DirectoryEntryHeader : ZipFileEntry
                 RelativeOffsetOfEntryHeader = zip64ExtraData.RelativeOffsetOfEntryHeader;
             }
         }
+
+        var unixTimeExtra = Extra.FirstOrDefault(u => u.Type == ExtraDataType.UnixTimeExtraField);
+
+        if (unixTimeExtra is not null)
+        {
+            // Tuple order is last modified time, last access time, and creation time.
+            var unixTimeTuple = ((UnixTimeExtraField)unixTimeExtra).UnicodeTimes;
+
+            if (unixTimeTuple.Item1.HasValue)
+            {
+                var dosTime = Utility.DateTimeToDosTime(unixTimeTuple.Item1.Value);
+
+                LastModifiedDate = (ushort)(dosTime >> 16);
+                LastModifiedTime = (ushort)(dosTime & 0x0FFFF);
+            }
+            else if (unixTimeTuple.Item2.HasValue)
+            {
+                var dosTime = Utility.DateTimeToDosTime(unixTimeTuple.Item2.Value);
+
+                LastModifiedDate = (ushort)(dosTime >> 16);
+                LastModifiedTime = (ushort)(dosTime & 0x0FFFF);
+            }
+            else if (unixTimeTuple.Item3.HasValue)
+            {
+                var dosTime = Utility.DateTimeToDosTime(unixTimeTuple.Item3.Value);
+
+                LastModifiedDate = (ushort)(dosTime >> 16);
+                LastModifiedTime = (ushort)(dosTime & 0x0FFFF);
+            }
+        }
     }
 
     internal ushort Version { get; private set; }

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

@@ -13,8 +13,8 @@ internal class LocalEntryHeader : ZipFileEntry
         Version = reader.ReadUInt16();
         Flags = (HeaderFlags)reader.ReadUInt16();
         CompressionMethod = (ZipCompressionMethod)reader.ReadUInt16();
-        LastModifiedTime = reader.ReadUInt16();
-        LastModifiedDate = reader.ReadUInt16();
+        OriginalLastModifiedTime = LastModifiedTime = reader.ReadUInt16();
+        OriginalLastModifiedDate = LastModifiedDate = reader.ReadUInt16();
         Crc = reader.ReadUInt32();
         CompressedSize = reader.ReadUInt32();
         UncompressedSize = reader.ReadUInt32();
@@ -42,8 +42,8 @@ internal class LocalEntryHeader : ZipFileEntry
 
         LoadExtra(extra);
 
-        var unicodePathExtra = Extra.FirstOrDefault(
-            u => u.Type == ExtraDataType.UnicodePathExtraField
+        var unicodePathExtra = Extra.FirstOrDefault(u =>
+            u.Type == ExtraDataType.UnicodePathExtraField
         );
         if (unicodePathExtra != null && ArchiveEncoding.Forced == null)
         {
@@ -64,6 +64,36 @@ internal class LocalEntryHeader : ZipFileEntry
                 UncompressedSize = zip64ExtraData.UncompressedSize;
             }
         }
+
+        var unixTimeExtra = Extra.FirstOrDefault(u => u.Type == ExtraDataType.UnixTimeExtraField);
+
+        if (unixTimeExtra is not null)
+        {
+            // Tuple order is last modified time, last access time, and creation time.
+            var unixTimeTuple = ((UnixTimeExtraField)unixTimeExtra).UnicodeTimes;
+
+            if (unixTimeTuple.Item1.HasValue)
+            {
+                var dosTime = Utility.DateTimeToDosTime(unixTimeTuple.Item1.Value);
+
+                LastModifiedDate = (ushort)(dosTime >> 16);
+                LastModifiedTime = (ushort)(dosTime & 0x0FFFF);
+            }
+            else if (unixTimeTuple.Item2.HasValue)
+            {
+                var dosTime = Utility.DateTimeToDosTime(unixTimeTuple.Item2.Value);
+
+                LastModifiedDate = (ushort)(dosTime >> 16);
+                LastModifiedTime = (ushort)(dosTime & 0x0FFFF);
+            }
+            else if (unixTimeTuple.Item3.HasValue)
+            {
+                var dosTime = Utility.DateTimeToDosTime(unixTimeTuple.Item3.Value);
+
+                LastModifiedDate = (ushort)(dosTime >> 16);
+                LastModifiedTime = (ushort)(dosTime & 0x0FFFF);
+            }
+        }
     }
 
     internal ushort Version { get; private set; }

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

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Buffers.Binary;
 using System.Text;
 
@@ -13,7 +13,8 @@ internal enum ExtraDataType : ushort
     // Third Party Mappings
     // -Info-ZIP Unicode Path Extra Field
     UnicodePathExtraField = 0x7075,
-    Zip64ExtendedInformationExtraField = 0x0001
+    Zip64ExtendedInformationExtraField = 0x0001,
+    UnixTimeExtraField = 0x5455
 }
 
 internal class ExtraData
@@ -145,6 +146,84 @@ internal sealed class Zip64ExtendedInformationExtraField : ExtraData
     public uint VolumeNumber { get; private set; }
 }
 
+internal sealed class UnixTimeExtraField : ExtraData
+{
+    public UnixTimeExtraField(ExtraDataType type, ushort length, byte[] dataBytes)
+        : base(type, length, dataBytes) { }
+
+    /// <summary>
+    /// The unix modified time, last access time, and creation time, if set.
+    /// </summary>
+    /// <remarks>Must return Tuple explicitly due to net462 support.</remarks>
+    internal Tuple<DateTime?, DateTime?, DateTime?> UnicodeTimes
+    {
+        get
+        {
+            // There has to be at least 5 byte for there to be a timestamp.
+            // 1 byte for flags and 4 bytes for a timestamp.
+            if (DataBytes is null || DataBytes.Length < 5)
+            {
+                return Tuple.Create<DateTime?, DateTime?, DateTime?>(null, null, null);
+            }
+
+            var flags = DataBytes[0];
+            var isModifiedTimeSpecified = (flags & 0x01) == 1;
+            var isLastAccessTimeSpecified = (flags & 0x02) == 1;
+            var isCreationTimeSpecified = (flags & 0x04) == 1;
+            var currentIndex = 1;
+            DateTime? modifiedTime = null;
+            DateTime? lastAccessTime = null;
+            DateTime? creationTime = null;
+
+            if (isModifiedTimeSpecified)
+            {
+                var modifiedEpochTime = BinaryPrimitives.ReadInt32LittleEndian(
+                    DataBytes.AsSpan(currentIndex, 4)
+                );
+
+                currentIndex += 4;
+                modifiedTime = DateTimeOffset.FromUnixTimeSeconds(modifiedEpochTime).UtcDateTime;
+            }
+
+            if (isLastAccessTimeSpecified)
+            {
+                if (currentIndex + 4 > DataBytes.Length)
+                {
+                    throw new ArchiveException("Invalid UnicodeExtraTime field");
+                }
+
+                var lastAccessEpochTime = BinaryPrimitives.ReadInt32LittleEndian(
+                    DataBytes.AsSpan(currentIndex, 4)
+                );
+
+                currentIndex += 4;
+                lastAccessTime = DateTimeOffset
+                    .FromUnixTimeSeconds(lastAccessEpochTime)
+                    .UtcDateTime;
+            }
+
+            if (isCreationTimeSpecified)
+            {
+                if (currentIndex + 4 > DataBytes.Length)
+                {
+                    throw new ArchiveException("Invalid UnicodeExtraTime field");
+                }
+
+                var creationTimeEpochTime = BinaryPrimitives.ReadInt32LittleEndian(
+                    DataBytes.AsSpan(currentIndex, 4)
+                );
+
+                currentIndex += 4;
+                creationTime = DateTimeOffset
+                    .FromUnixTimeSeconds(creationTimeEpochTime)
+                    .UtcDateTime;
+            }
+
+            return Tuple.Create(modifiedTime, lastAccessTime, creationTime);
+        }
+    }
+}
+
 internal static class LocalEntryHeaderExtraFactory
 {
     internal static ExtraData Create(ExtraDataType type, ushort length, byte[] extraData) =>
@@ -154,6 +233,7 @@ internal static class LocalEntryHeaderExtraFactory
                 => new ExtraUnicodePathExtraField(type, length, extraData),
             ExtraDataType.Zip64ExtendedInformationExtraField
                 => new Zip64ExtendedInformationExtraField(type, length, extraData),
+            ExtraDataType.UnixTimeExtraField => new UnixTimeExtraField(type, length, extraData),
             _ => new ExtraData(type, length, extraData)
         };
 }

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

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Buffers.Binary;
 using System.Collections.Generic;
@@ -20,21 +18,21 @@ internal abstract class ZipFileEntry : ZipHeader
     {
         get
         {
-            if (Name.EndsWith('/'))
+            if (Name?.EndsWith('/') ?? false)
             {
                 return true;
             }
 
             //.NET Framework 4.5 : System.IO.Compression::CreateFromDirectory() probably writes backslashes to headers
-            return CompressedSize == 0 && UncompressedSize == 0 && Name.EndsWith('\\');
+            return CompressedSize == 0 && UncompressedSize == 0 && (Name?.EndsWith('\\') ?? false);
         }
     }
 
-    internal Stream PackedStream { get; set; }
+    internal Stream? PackedStream { get; set; }
 
     internal ArchiveEncoding ArchiveEncoding { get; }
 
-    internal string Name { get; set; }
+    internal string? Name { get; set; }
 
     internal HeaderFlags Flags { get; set; }
 
@@ -48,7 +46,7 @@ internal abstract class ZipFileEntry : ZipHeader
 
     internal List<ExtraData> Extra { get; set; }
 
-    public string Password { get; set; }
+    public string? Password { get; set; }
 
     internal PkwareTraditionalEncryptionData ComposeEncryptionData(Stream archiveStream)
     {
@@ -65,10 +63,28 @@ internal abstract class ZipFileEntry : ZipHeader
         return encryptionData;
     }
 
-    internal WinzipAesEncryptionData WinzipAesEncryptionData { get; set; }
+    internal WinzipAesEncryptionData? WinzipAesEncryptionData { get; set; }
 
+    /// <summary>
+    /// The last modified date as read from the Local or Central Directory header.
+    /// </summary>
+    internal ushort OriginalLastModifiedDate { get; set; }
+
+    /// <summary>
+    /// The last modified date from the UnixTimeExtraField, if present, or the
+    /// Local or Cental Directory header, if not.
+    /// </summary>
     internal ushort LastModifiedDate { get; set; }
 
+    /// <summary>
+    /// The last modified time as read from the Local or Central Directory header.
+    /// </summary>
+    internal ushort OriginalLastModifiedTime { get; set; }
+
+    /// <summary>
+    /// The last modified time from the UnixTimeExtraField, if present, or the
+    /// Local or Cental Directory header, if not.
+    /// </summary>
     internal ushort LastModifiedTime { get; set; }
 
     internal uint Crc { get; set; }
@@ -101,7 +117,7 @@ internal abstract class ZipFileEntry : ZipHeader
         }
     }
 
-    internal ZipFilePart Part { get; set; }
+    internal ZipFilePart? Part { get; set; }
 
     internal bool IsZip64 => CompressedSize >= uint.MaxValue;
 }

src/SharpCompress/Common/Zip/PkwareTraditionalCryptoStream.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.IO;
 
 namespace SharpCompress.Common.Zip;
@@ -87,10 +87,7 @@ internal class PkwareTraditionalCryptoStream : Stream
         _stream.Write(encrypted, 0, encrypted.Length);
     }
 
-    public override void Flush()
-    {
-        //throw new NotSupportedException();
-    }
+    public override void Flush() { }
 
     public override long Seek(long offset, SeekOrigin origin) => throw new NotSupportedException();
 

src/SharpCompress/Common/Zip/PkwareTraditionalEncryptionData.cs

@@ -6,7 +6,7 @@ namespace SharpCompress.Common.Zip;
 
 internal class PkwareTraditionalEncryptionData
 {
-    private static readonly CRC32 CRC32 = new CRC32();
+    private static readonly CRC32 CRC32 = new();
     private readonly uint[] _keys = { 0x12345678, 0x23456789, 0x34567890 };
     private readonly ArchiveEncoding _archiveEncoding;
 
@@ -39,7 +39,7 @@ internal class PkwareTraditionalEncryptionData
             {
                 throw new CryptographicException("The password did not match.");
             }
-            if (plainTextHeader[11] != (byte)((header.LastModifiedTime >> 8) & 0xff))
+            if (plainTextHeader[11] != (byte)((header.OriginalLastModifiedTime >> 8) & 0xff))
             {
                 throw new CryptographicException("The password did not match.");
             }
@@ -103,7 +103,7 @@ internal class PkwareTraditionalEncryptionData
 
     internal byte[] StringToByteArray(string value)
     {
-        var a = _archiveEncoding.Password.GetBytes(value);
+        var a = _archiveEncoding.GetPasswordEncoding().GetBytes(value);
         return a;
     }
 

src/SharpCompress/Common/Zip/SeekableZipFilePart.cs

@@ -42,16 +42,16 @@ internal class SeekableZipFilePart : ZipFilePart
 
     protected override Stream CreateBaseStream()
     {
-        BaseStream.Position = Header.DataStartPosition!.Value;
+        BaseStream.Position = Header.DataStartPosition.NotNull();
 
         if (
             (Header.CompressedSize == 0)
             && FlagUtility.HasFlag(Header.Flags, HeaderFlags.UsePostDataDescriptor)
-            && (_directoryEntryHeader?.HasData == true)
-            && (_directoryEntryHeader?.CompressedSize != 0)
+            && _directoryEntryHeader.HasData
+            && (_directoryEntryHeader.CompressedSize != 0)
         )
         {
-            return new ReadOnlySubStream(BaseStream, _directoryEntryHeader!.CompressedSize);
+            return new ReadOnlySubStream(BaseStream, _directoryEntryHeader.CompressedSize);
         }
 
         return BaseStream;

src/SharpCompress/Common/Zip/StreamingZipFilePart.cs

@@ -13,7 +13,7 @@ internal sealed class StreamingZipFilePart : ZipFilePart
     internal StreamingZipFilePart(ZipFileEntry header, Stream stream)
         : base(header, stream) { }
 
-    protected override Stream CreateBaseStream() => Header.PackedStream;
+    protected override Stream CreateBaseStream() => Header.PackedStream.NotNull();
 
     internal override Stream GetCompressedStream()
     {

src/SharpCompress/Common/Zip/StreamingZipHeaderFactory.cs

@@ -15,10 +15,7 @@ internal class StreamingZipHeaderFactory : ZipHeaderFactory
         ArchiveEncoding archiveEncoding,
         IEnumerable<ZipEntry>? entries
     )
-        : base(StreamingMode.Streaming, password, archiveEncoding)
-    {
-        _entries = entries;
-    }
+        : base(StreamingMode.Streaming, password, archiveEncoding) => _entries = entries;
 
     internal IEnumerable<ZipHeader> ReadStreamHeader(Stream stream)
     {
@@ -45,6 +42,10 @@ internal class StreamingZipHeaderFactory : ZipHeaderFactory
                 )
             )
             {
+                if (_lastEntryHeader.Part is null)
+                {
+                    continue;
+                }
                 reader = ((StreamingZipFilePart)_lastEntryHeader.Part).FixStreamedFileLocation(
                     ref rewindableStream
                 );
@@ -97,13 +98,12 @@ internal class StreamingZipHeaderFactory : ZipHeaderFactory
             if (header.ZipHeaderType == ZipHeaderType.LocalEntry)
             {
                 var local_header = ((LocalEntryHeader)header);
-                var dir_header = _entries?.FirstOrDefault(
-                    entry =>
-                        entry.Key == local_header.Name
-                        && local_header.CompressedSize == 0
-                        && local_header.UncompressedSize == 0
-                        && local_header.Crc == 0
-                        && local_header.IsDirectory == false
+                var dir_header = _entries?.FirstOrDefault(entry =>
+                    entry.Key == local_header.Name
+                    && local_header.CompressedSize == 0
+                    && local_header.UncompressedSize == 0
+                    && local_header.Crc == 0
+                    && local_header.IsDirectory == false
                 );
 
                 if (dir_header != null)

src/SharpCompress/Common/Zip/WinzipAesCryptoStream.cs

@@ -73,7 +73,7 @@ internal class WinzipAesCryptoStream : Stream
         }
     }
 
-    public override void Flush() => throw new NotSupportedException();
+    public override void Flush() { }
 
     public override int Read(byte[] buffer, int offset, int count)
     {

src/SharpCompress/Common/Zip/WinzipAesEncryptionData.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Buffers.Binary;
 using System.Security.Cryptography;
@@ -10,12 +8,7 @@ internal class WinzipAesEncryptionData
 {
     private const int RFC2898_ITERATIONS = 1000;
 
-    private readonly byte[] _salt;
     private readonly WinzipAesKeySize _keySize;
-    private readonly byte[] _passwordVerifyValue;
-    private readonly string _password;
-
-    private byte[] _generatedVerifyValue;
 
     internal WinzipAesEncryptionData(
         WinzipAesKeySize keySize,
@@ -25,10 +18,28 @@ internal class WinzipAesEncryptionData
     )
     {
         _keySize = keySize;
-        _salt = salt;
-        _passwordVerifyValue = passwordVerifyValue;
-        _password = password;
-        Initialize();
+
+#if NETFRAMEWORK || NETSTANDARD2_0
+        var rfc2898 = new Rfc2898DeriveBytes(password, salt, RFC2898_ITERATIONS);
+#else
+        var rfc2898 = new Rfc2898DeriveBytes(
+            password,
+            salt,
+            RFC2898_ITERATIONS,
+            HashAlgorithmName.SHA1
+        );
+#endif
+
+        KeyBytes = rfc2898.GetBytes(KeySizeInBytes); // 16 or 24 or 32 ???
+        IvBytes = rfc2898.GetBytes(KeySizeInBytes);
+        var generatedVerifyValue = rfc2898.GetBytes(2);
+
+        var verify = BinaryPrimitives.ReadInt16LittleEndian(passwordVerifyValue);
+        var generated = BinaryPrimitives.ReadInt16LittleEndian(generatedVerifyValue);
+        if (verify != generated)
+        {
+            throw new InvalidFormatException("bad password");
+        }
     }
 
     internal byte[] IvBytes { get; set; }
@@ -45,32 +56,4 @@ internal class WinzipAesEncryptionData
             WinzipAesKeySize.KeySize256 => 32,
             _ => throw new InvalidOperationException(),
         };
-
-    private void Initialize()
-    {
-#if NET7_0
-        var rfc2898 = new Rfc2898DeriveBytes(
-            _password,
-            _salt,
-            RFC2898_ITERATIONS,
-            HashAlgorithmName.SHA1
-        );
-#else
-        var rfc2898 = new Rfc2898DeriveBytes(_password, _salt, RFC2898_ITERATIONS);
-#endif
-
-        KeyBytes = rfc2898.GetBytes(KeySizeInBytes); // 16 or 24 or 32 ???
-        IvBytes = rfc2898.GetBytes(KeySizeInBytes);
-        _generatedVerifyValue = rfc2898.GetBytes(2);
-
-        var verify = BinaryPrimitives.ReadInt16LittleEndian(_passwordVerifyValue);
-        if (_password != null)
-        {
-            var generated = BinaryPrimitives.ReadInt16LittleEndian(_generatedVerifyValue);
-            if (verify != generated)
-            {
-                throw new InvalidFormatException("bad password");
-            }
-        }
-    }
 }

src/SharpCompress/Common/Zip/ZipCompressionMethod.cs

@@ -3,6 +3,7 @@ namespace SharpCompress.Common.Zip;
 internal enum ZipCompressionMethod
 {
     None = 0,
+    Shrink = 1,
     Deflate = 8,
     Deflate64 = 9,
     BZip2 = 12,

src/SharpCompress/Common/Zip/ZipEntry.cs

@@ -1,5 +1,3 @@
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using SharpCompress.Common.Zip.Headers;
@@ -8,67 +6,43 @@ namespace SharpCompress.Common.Zip;
 
 public class ZipEntry : Entry
 {
-    private readonly ZipFilePart _filePart;
+    private readonly ZipFilePart? _filePart;
 
-    internal ZipEntry(ZipFilePart filePart)
+    internal ZipEntry(ZipFilePart? filePart)
     {
-        if (filePart != null)
+        if (filePart == null)
         {
-            _filePart = filePart;
-            LastModifiedTime = Utility.DosDateToDateTime(
-                filePart.Header.LastModifiedDate,
-                filePart.Header.LastModifiedTime
-            );
+            return;
         }
+        _filePart = filePart;
+        LastModifiedTime = Utility.DosDateToDateTime(
+            filePart.Header.LastModifiedDate,
+            filePart.Header.LastModifiedTime
+        );
     }
 
-    public override CompressionType CompressionType
-    {
-        get
+    public override CompressionType CompressionType =>
+        _filePart?.Header.CompressionMethod switch
         {
-            switch (_filePart.Header.CompressionMethod)
-            {
-                case ZipCompressionMethod.BZip2:
-                {
-                    return CompressionType.BZip2;
-                }
-                case ZipCompressionMethod.Deflate:
-                {
-                    return CompressionType.Deflate;
-                }
-                case ZipCompressionMethod.Deflate64:
-                {
-                    return CompressionType.Deflate64;
-                }
-                case ZipCompressionMethod.LZMA:
-                {
-                    return CompressionType.LZMA;
-                }
-                case ZipCompressionMethod.PPMd:
-                {
-                    return CompressionType.PPMd;
-                }
-                case ZipCompressionMethod.None:
-                {
-                    return CompressionType.None;
-                }
-                default:
-                {
-                    return CompressionType.Unknown;
-                }
-            }
-        }
-    }
+            ZipCompressionMethod.BZip2 => CompressionType.BZip2,
+            ZipCompressionMethod.Deflate => CompressionType.Deflate,
+            ZipCompressionMethod.Deflate64 => CompressionType.Deflate64,
+            ZipCompressionMethod.LZMA => CompressionType.LZMA,
+            ZipCompressionMethod.PPMd => CompressionType.PPMd,
+            ZipCompressionMethod.None => CompressionType.None,
+            ZipCompressionMethod.Shrink => CompressionType.Shrink,
+            _ => CompressionType.Unknown
+        };
 
-    public override long Crc => _filePart.Header.Crc;
+    public override long Crc => _filePart?.Header.Crc ?? 0;
 
-    public override string Key => _filePart.Header.Name;
+    public override string? Key => _filePart?.Header.Name;
 
-    public override string LinkTarget => null;
+    public override string? LinkTarget => null;
 
-    public override long CompressedSize => _filePart.Header.CompressedSize;
+    public override long CompressedSize => _filePart?.Header.CompressedSize ?? 0;
 
-    public override long Size => _filePart.Header.UncompressedSize;
+    public override long Size => _filePart?.Header.UncompressedSize ?? 0;
 
     public override DateTime? LastModifiedTime { get; }
 
@@ -79,11 +53,11 @@ public class ZipEntry : Entry
     public override DateTime? ArchivedTime => null;
 
     public override bool IsEncrypted =>
-        FlagUtility.HasFlag(_filePart.Header.Flags, HeaderFlags.Encrypted);
+        FlagUtility.HasFlag(_filePart?.Header.Flags ?? HeaderFlags.None, HeaderFlags.Encrypted);
 
-    public override bool IsDirectory => _filePart.Header.IsDirectory;
+    public override bool IsDirectory => _filePart?.Header.IsDirectory ?? false;
 
     public override bool IsSplitAfter => false;
 
-    internal override IEnumerable<FilePart> Parts => _filePart.AsEnumerable<FilePart>();
+    internal override IEnumerable<FilePart> Parts => _filePart.Empty();
 }

src/SharpCompress/Common/Zip/ZipFilePart.cs

@@ -9,6 +9,7 @@ using SharpCompress.Compressors.Deflate;
 using SharpCompress.Compressors.Deflate64;
 using SharpCompress.Compressors.LZMA;
 using SharpCompress.Compressors.PPMd;
+using SharpCompress.Compressors.Shrink;
 using SharpCompress.Compressors.Xz;
 using SharpCompress.IO;
 using ZstdSharp;
@@ -28,7 +29,7 @@ internal abstract class ZipFilePart : FilePart
     internal Stream BaseStream { get; }
     internal ZipFileEntry Header { get; set; }
 
-    internal override string FilePartName => Header.Name;
+    internal override string? FilePartName => Header.Name;
 
     internal override Stream GetCompressedStream()
     {
@@ -79,6 +80,15 @@ internal abstract class ZipFilePart : FilePart
 
                 return new DataDescriptorStream(stream);
             }
+            case ZipCompressionMethod.Shrink:
+            {
+                return new ShrinkStream(
+                    stream,
+                    CompressionMode.Decompress,
+                    Header.CompressedSize,
+                    Header.UncompressedSize
+                );
+            }
             case ZipCompressionMethod.Deflate:
             {
                 return new DeflateStream(stream, CompressionMode.Decompress);
@@ -192,6 +202,7 @@ internal abstract class ZipFilePart : FilePart
             switch (Header.CompressionMethod)
             {
                 case ZipCompressionMethod.None:
+                case ZipCompressionMethod.Shrink:
                 case ZipCompressionMethod.Deflate:
                 case ZipCompressionMethod.Deflate64:
                 case ZipCompressionMethod.BZip2:

src/SharpCompress/Common/Zip/ZipHeaderFactory.cs

@@ -55,7 +55,13 @@ internal class ZipHeaderFactory
             }
             case POST_DATA_DESCRIPTOR:
             {
-                if (FlagUtility.HasFlag(_lastEntryHeader!.Flags, HeaderFlags.UsePostDataDescriptor))
+                if (
+                    FlagUtility.HasFlag(
+                        _lastEntryHeader.NotNull().Flags,
+                        HeaderFlags.UsePostDataDescriptor
+                    )
+                    && _lastEntryHeader != null
+                )
                 {
                     _lastEntryHeader.Crc = reader.ReadUInt32();
                     _lastEntryHeader.CompressedSize = zip64
@@ -142,9 +148,9 @@ internal class ZipHeaderFactory
 
             if (entryHeader.CompressionMethod == ZipCompressionMethod.WinzipAes)
             {
-                var data = entryHeader
-                    .Extra
-                    .SingleOrDefault(x => x.Type == ExtraDataType.WinZipAes);
+                var data = entryHeader.Extra.SingleOrDefault(x =>
+                    x.Type == ExtraDataType.WinZipAes
+                );
                 if (data != null)
                 {
                     var keySize = (WinzipAesKeySize)data.DataBytes[4];

src/SharpCompress/Compressors/BZip2/BZip2Stream.cs

@@ -69,7 +69,7 @@ public sealed class BZip2Stream : Stream
 
     public override void SetLength(long value) => stream.SetLength(value);
 
-#if !NETFRAMEWORK && !NETSTANDARD2_0
+#if !NETFRAMEWORK&& !NETSTANDARD2_0
 
     public override int Read(Span<byte> buffer) => stream.Read(buffer);
 

src/SharpCompress/Compressors/BZip2/CBZip2InputStream.cs

@@ -87,7 +87,7 @@ internal class CBZip2InputStream : Stream
 
     private int bsBuff;
     private int bsLive;
-    private readonly CRC mCrc = new CRC();
+    private readonly CRC mCrc = new();
 
     private readonly bool[] inUse = new bool[256];
     private int nInUse;

src/SharpCompress/Compressors/BZip2/CBZip2OutputStream.cs

@@ -284,7 +284,7 @@ internal sealed class CBZip2OutputStream : Stream
     private int bytesOut;
     private int bsBuff;
     private int bsLive;
-    private readonly CRC mCrc = new CRC();
+    private readonly CRC mCrc = new();
 
     private readonly bool[] inUse = new bool[256];
     private int nInUse;

src/SharpCompress/Compressors/Deflate/DeflateManager.cs

@@ -342,9 +342,9 @@ internal sealed partial class DeflateManager
     private readonly short[] dyn_dtree; // distance tree
     private readonly short[] bl_tree; // Huffman tree for bit lengths
 
-    private readonly Tree treeLiterals = new Tree(); // desc for literal tree
-    private readonly Tree treeDistances = new Tree(); // desc for distance tree
-    private readonly Tree treeBitLengths = new Tree(); // desc for bit length tree
+    private readonly Tree treeLiterals = new(); // desc for literal tree
+    private readonly Tree treeDistances = new(); // desc for distance tree
+    private readonly Tree treeBitLengths = new(); // desc for bit length tree
 
     // number of codes at each bit length for an optimal tree
     private readonly short[] bl_count = new short[InternalConstants.MAX_BITS + 1];
@@ -1787,21 +1787,14 @@ internal sealed partial class DeflateManager
         return status == BUSY_STATE ? ZlibConstants.Z_DATA_ERROR : ZlibConstants.Z_OK;
     }
 
-    private void SetDeflater()
-    {
-        switch (config.Flavor)
+    private void SetDeflater() =>
+        DeflateFunction = config.Flavor switch
         {
-            case DeflateFlavor.Store:
-                DeflateFunction = DeflateNone;
-                break;
-            case DeflateFlavor.Fast:
-                DeflateFunction = DeflateFast;
-                break;
-            case DeflateFlavor.Slow:
-                DeflateFunction = DeflateSlow;
-                break;
-        }
-    }
+            DeflateFlavor.Store => DeflateNone,
+            DeflateFlavor.Fast => DeflateFast,
+            DeflateFlavor.Slow => DeflateSlow,
+            _ => DeflateFunction
+        };
 
     internal int SetParams(CompressionLevel level, CompressionStrategy strategy)
     {

src/SharpCompress/Compressors/Deflate/DeflateStream.cs

@@ -366,9 +366,5 @@ public class DeflateStream : Stream
     #endregion
 
     public MemoryStream InputBuffer =>
-        new MemoryStream(
-            _baseStream._z.InputBuffer,
-            _baseStream._z.NextIn,
-            _baseStream._z.AvailableBytesIn
-        );
+        new(_baseStream._z.InputBuffer, _baseStream._z.NextIn, _baseStream._z.AvailableBytesIn);
 }

src/SharpCompress/Compressors/Deflate/GZipStream.cs

@@ -35,15 +35,7 @@ namespace SharpCompress.Compressors.Deflate;
 
 public class GZipStream : Stream
 {
-    internal static readonly DateTime UNIX_EPOCH = new DateTime(
-        1970,
-        1,
-        1,
-        0,
-        0,
-        0,
-        DateTimeKind.Utc
-    );
+    internal static readonly DateTime UNIX_EPOCH = new(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
 
     private string? _comment;
     private string? _fileName;

src/SharpCompress/Compressors/Deflate/Inflate.cs

@@ -105,11 +105,11 @@ internal sealed class InflateBlocks
     internal int[] blens; // bit lengths of codes
     internal uint check; // check on output
     internal object checkfn; // check function
-    internal InflateCodes codes = new InflateCodes(); // if CODES, current state
+    internal InflateCodes codes = new(); // if CODES, current state
     internal int end; // one byte after sliding window
     internal int[] hufts; // single malloc for tree space
     internal int index; // index into blens (or border)
-    internal InfTree inftree = new InfTree();
+    internal InfTree inftree = new();
     internal int last; // true if this block is the last block
     internal int left; // if STORED, bytes left to copy
     private InflateBlockMode mode; // current inflate_block mode

src/SharpCompress/Compressors/Deflate/ZlibBaseStream.cs

@@ -102,7 +102,7 @@ internal class ZlibBaseStream : Stream
         {
             if (_z is null)
             {
-                bool wantRfc1950Header = (_flavor == ZlibStreamFlavor.ZLIB);
+                var wantRfc1950Header = (_flavor == ZlibStreamFlavor.ZLIB);
                 _z = new ZlibCodec();
                 if (_compressionMode == CompressionMode.Decompress)
                 {
@@ -147,13 +147,13 @@ internal class ZlibBaseStream : Stream
         z.InputBuffer = buffer;
         _z.NextIn = offset;
         _z.AvailableBytesIn = count;
-        bool done = false;
+        var done = false;
         do
         {
             _z.OutputBuffer = workingBuffer;
             _z.NextOut = 0;
             _z.AvailableBytesOut = _workingBuffer.Length;
-            int rc = (_wantCompress) ? _z.Deflate(_flushMode) : _z.Inflate(_flushMode);
+            var rc = (_wantCompress) ? _z.Deflate(_flushMode) : _z.Inflate(_flushMode);
             if (rc != ZlibConstants.Z_OK && rc != ZlibConstants.Z_STREAM_END)
             {
                 throw new ZlibException((_wantCompress ? "de" : "in") + "flating: " + _z.Message);
@@ -181,18 +181,18 @@ internal class ZlibBaseStream : Stream
 
         if (_streamMode == StreamMode.Writer)
         {
-            bool done = false;
+            var done = false;
             do
             {
                 _z.OutputBuffer = workingBuffer;
                 _z.NextOut = 0;
                 _z.AvailableBytesOut = _workingBuffer.Length;
-                int rc =
+                var rc =
                     (_wantCompress) ? _z.Deflate(FlushType.Finish) : _z.Inflate(FlushType.Finish);
 
                 if (rc != ZlibConstants.Z_STREAM_END && rc != ZlibConstants.Z_OK)
                 {
-                    string verb = (_wantCompress ? "de" : "in") + "flating";
+                    var verb = (_wantCompress ? "de" : "in") + "flating";
                     if (_z.Message is null)
                     {
                         throw new ZlibException(String.Format("{0}: (rc = {1})", verb, rc));
@@ -225,7 +225,7 @@ internal class ZlibBaseStream : Stream
                     Span<byte> intBuf = stackalloc byte[4];
                     BinaryPrimitives.WriteInt32LittleEndian(intBuf, crc.Crc32Result);
                     _stream.Write(intBuf);
-                    int c2 = (int)(crc.TotalBytesRead & 0x00000000FFFFFFFF);
+                    var c2 = (int)(crc.TotalBytesRead & 0x00000000FFFFFFFF);
                     BinaryPrimitives.WriteInt32LittleEndian(intBuf, c2);
                     _stream.Write(intBuf);
                 }
@@ -256,8 +256,8 @@ internal class ZlibBaseStream : Stream
                     {
                         // Make sure we have read to the end of the stream
                         _z.InputBuffer.AsSpan(_z.NextIn, _z.AvailableBytesIn).CopyTo(trailer);
-                        int bytesNeeded = 8 - _z.AvailableBytesIn;
-                        int bytesRead = _stream.Read(
+                        var bytesNeeded = 8 - _z.AvailableBytesIn;
+                        var bytesRead = _stream.Read(
                             trailer.Slice(_z.AvailableBytesIn, bytesNeeded)
                         );
                         if (bytesNeeded != bytesRead)
@@ -275,10 +275,10 @@ internal class ZlibBaseStream : Stream
                         _z.InputBuffer.AsSpan(_z.NextIn, trailer.Length).CopyTo(trailer);
                     }
 
-                    Int32 crc32_expected = BinaryPrimitives.ReadInt32LittleEndian(trailer);
-                    Int32 crc32_actual = crc.Crc32Result;
-                    Int32 isize_expected = BinaryPrimitives.ReadInt32LittleEndian(trailer.Slice(4));
-                    Int32 isize_actual = (Int32)(_z.TotalBytesOut & 0x00000000FFFFFFFF);
+                    var crc32_expected = BinaryPrimitives.ReadInt32LittleEndian(trailer);
+                    var crc32_actual = crc.Crc32Result;
+                    var isize_expected = BinaryPrimitives.ReadInt32LittleEndian(trailer.Slice(4));
+                    var isize_actual = (Int32)(_z.TotalBytesOut & 0x00000000FFFFFFFF);
 
                     if (crc32_actual != crc32_expected)
                     {
@@ -380,11 +380,11 @@ internal class ZlibBaseStream : Stream
     private string ReadZeroTerminatedString()
     {
         var list = new List<byte>();
-        bool done = false;
+        var done = false;
         do
         {
             // workitem 7740
-            int n = _stream.Read(_buf1, 0, 1);
+            var n = _stream.Read(_buf1, 0, 1);
             if (n != 1)
             {
                 throw new ZlibException("Unexpected EOF reading GZIP header.");
@@ -398,17 +398,17 @@ internal class ZlibBaseStream : Stream
                 list.Add(_buf1[0]);
             }
         } while (!done);
-        byte[] buffer = list.ToArray();
+        var buffer = list.ToArray();
         return _encoding.GetString(buffer, 0, buffer.Length);
     }
 
     private int _ReadAndValidateGzipHeader()
     {
-        int totalBytesRead = 0;
+        var totalBytesRead = 0;
 
         // read the header on the first read
         Span<byte> header = stackalloc byte[10];
-        int n = _stream.Read(header);
+        var n = _stream.Read(header);
 
         // workitem 8501: handle edge case (decompress empty stream)
         if (n == 0)
@@ -426,7 +426,7 @@ internal class ZlibBaseStream : Stream
             throw new ZlibException("Bad GZIP header.");
         }
 
-        int timet = BinaryPrimitives.ReadInt32LittleEndian(header.Slice(4));
+        var timet = BinaryPrimitives.ReadInt32LittleEndian(header.Slice(4));
         _GzipMtime = TarHeader.EPOCH.AddSeconds(timet);
         totalBytesRead += n;
         if ((header[3] & 0x04) == 0x04)
@@ -435,8 +435,8 @@ internal class ZlibBaseStream : Stream
             n = _stream.Read(header.Slice(0, 2)); // 2-byte length field
             totalBytesRead += n;
 
-            short extraLength = (short)(header[0] + header[1] * 256);
-            byte[] extra = new byte[extraLength];
+            var extraLength = (short)(header[0] + header[1] * 256);
+            var extra = new byte[extraLength];
             n = _stream.Read(extra, 0, extra.Length);
             if (n != extraLength)
             {
@@ -498,7 +498,7 @@ internal class ZlibBaseStream : Stream
             throw new ZlibException("Cannot Read after Writing.");
         }
 
-        int rc = 0;
+        var rc = 0;
 
         // set up the output of the deflate/inflate codec:
         _z.OutputBuffer = buffer;

src/SharpCompress/Compressors/Deflate64/Deflate64Stream.cs

@@ -118,8 +118,8 @@ public sealed class Deflate64Stream : Stream
         EnsureNotDisposed();
 
         int bytesRead;
-        int currentOffset = offset;
-        int remainingCount = count;
+        var currentOffset = offset;
+        var remainingCount = count;
 
         while (true)
         {
@@ -142,7 +142,7 @@ public sealed class Deflate64Stream : Stream
                 break;
             }
 
-            int bytes = _stream.Read(_buffer, 0, _buffer.Length);
+            var bytes = _stream.Read(_buffer, 0, _buffer.Length);
             if (bytes <= 0)
             {
                 break;

src/SharpCompress/Compressors/Deflate64/DeflateInput.cs

@@ -22,7 +22,7 @@ internal sealed class DeflateInput
         Debug.Assert(StartIndex + Count <= Buffer.Length, "Input buffer is in invalid state!");
     }
 
-    internal InputState DumpState() => new InputState(Count, StartIndex);
+    internal InputState DumpState() => new(Count, StartIndex);
 
     internal void RestoreState(InputState state)
     {

src/SharpCompress/Compressors/Deflate64/HuffmanTree.cs

@@ -42,11 +42,9 @@ internal sealed class HuffmanTree
     private readonly int _tableMask;
 
     // huffman tree for static block
-    public static HuffmanTree StaticLiteralLengthTree { get; } =
-        new HuffmanTree(GetStaticLiteralTreeLength());
+    public static HuffmanTree StaticLiteralLengthTree { get; } = new(GetStaticLiteralTreeLength());
 
-    public static HuffmanTree StaticDistanceTree { get; } =
-        new HuffmanTree(GetStaticDistanceTreeLength());
+    public static HuffmanTree StaticDistanceTree { get; } = new(GetStaticDistanceTreeLength());
 
     public HuffmanTree(byte[] codeLengths)
     {