Some corrections to latest changes

Author: LTRData

Library/DiscUtils.Core/Compression/LZNT1.cs

@@ -29,6 +29,7 @@
 //
 
 using System;
+using System.Buffers;
 using System.Collections.Immutable;
 using DiscUtils.Streams;
 
@@ -41,7 +42,7 @@ namespace DiscUtils.Compression;
 /// Due to apparent bugs in Window's LZNT1 decompressor, it is <b>strongly</b> recommended that
 /// only the block size of 4096 is used.  Other block sizes corrupt data on decompression.
 /// </remarks>
-internal sealed class LZNT1 : BlockCompressor
+public sealed class LZNT1 : BlockCompressor
 {
     private const ushort SubBlockIsCompressedFlag = 0x8000;
     private const ushort SubBlockSizeMask = 0x0fff;
@@ -301,20 +302,28 @@ public override int Decompress(ReadOnlySpan<byte> source, Span<byte> decompresse
 
     private static ImmutableArray<byte> CalcCompressionBits()
     {
-        var result = ImmutableArray.CreateBuilder<byte>(4096);
-        byte offsetBits = 0;
+        var result = ArrayPool<byte>.Shared.Rent(4096);
 
-        var y = 0x10;
-        for (var x = 0; x < 4096; x++)
+        try
         {
-            result[x] = (byte)(4 + offsetBits);
-            if (x == y)
+            byte offsetBits = 0;
+
+            var y = 0x10;
+            for (var x = 0; x < 4096; x++)
             {
-                y <<= 1;
-                offsetBits++;
+                result[x] = (byte)(4 + offsetBits);
+                if (x == y)
+                {
+                    y <<= 1;
+                    offsetBits++;
+                }
             }
-        }
 
-        return result.ToImmutable();
+            return ImmutableArray.Create(result, 0, 4096);
+        }
+        finally
+        {
+            ArrayPool<byte>.Shared.Return(result);
+        }
     }
 }

Library/DiscUtils.Core/Compression/XpressStream.cs

@@ -33,7 +33,7 @@ namespace DiscUtils.Compression;
 /// </summary>
 /// <remarks>This class is optimized for the case where the entire stream contents
 /// fit into memory, it is not suitable for unbounded streams.</remarks>
-internal class XpressStream : ReadOnlyCompatibilityStream
+public class XpressStream : ReadOnlyCompatibilityStream
 {
     private readonly byte[] _buffer;
     private readonly BufferedStream _compressedStream;

Library/DiscUtils.Core/Internal/Crc32BigEndian.cs

@@ -34,14 +34,14 @@ internal sealed class Crc32BigEndian : Crc32
 
     static Crc32BigEndian()
     {
-        var tables = ImmutableArray.CreateBuilder<ImmutableArray<uint>>(4);
+        var tables = new ImmutableArray<uint>[4];
 
         tables[(int)Crc32Algorithm.Common] = CalcTable(0x04C11DB7);
         tables[(int)Crc32Algorithm.Castagnoli] = CalcTable(0x1EDC6F41);
         tables[(int)Crc32Algorithm.Koopman] = CalcTable(0x741B8CD7);
         tables[(int)Crc32Algorithm.Aeronautical] = CalcTable(0x814141AB);
 
-        Tables = tables.ToImmutable();
+        Tables = tables.ToImmutableArray();
     }
 
     public Crc32BigEndian(Crc32Algorithm algorithm)
@@ -64,7 +64,7 @@ public override void Process(ReadOnlySpan<byte> buffer)
 
     private static ImmutableArray<uint> CalcTable(uint polynomial)
     {
-        var table = ImmutableArray.CreateBuilder<uint>(256);
+        Span<uint> table = stackalloc uint[256];
 
         for (uint i = 0; i < 256; ++i)
         {
@@ -85,7 +85,7 @@ private static ImmutableArray<uint> CalcTable(uint polynomial)
             table[(int)i] = crc;
         }
 
-        return table.ToImmutable();
+        return table.ToImmutableArray();
     }
 
     private static uint Process(ImmutableArray<uint> table, uint accumulator, ReadOnlySpan<byte> buffer)

Library/DiscUtils.Core/Internal/Crc32LittleEndian.cs

@@ -34,14 +34,14 @@ internal sealed class Crc32LittleEndian : Crc32
 
     static Crc32LittleEndian()
     {
-        var tables = ImmutableArray.CreateBuilder<ImmutableArray<uint>>(4);
+        var tables = new ImmutableArray<uint>[4];
 
         tables[(int)Crc32Algorithm.Common] = CalcTable(0xEDB88320);
         tables[(int)Crc32Algorithm.Castagnoli] = CalcTable(0x82F63B78);
         tables[(int)Crc32Algorithm.Koopman] = CalcTable(0xEB31D82E);
         tables[(int)Crc32Algorithm.Aeronautical] = CalcTable(0xD5828281);
 
-        Tables = tables.ToImmutable();
+        Tables = tables.ToImmutableArray();
     }
 
     public Crc32LittleEndian(Crc32Algorithm algorithm)
@@ -64,9 +64,8 @@ public override void Process(ReadOnlySpan<byte> buffer)
 
     private static ImmutableArray<uint> CalcTable(uint polynomial)
     {
-        var table = ImmutableArray.CreateBuilder<uint>(256);
+        Span<uint> table = stackalloc uint[256];
 
-        table[0] = 0;
         for (uint i = 0; i <= 255; ++i)
         {
             var crc = i;
@@ -86,7 +85,7 @@ private static ImmutableArray<uint> CalcTable(uint polynomial)
             table[(int)i] = crc;
         }
 
-        return table.ToImmutable();
+        return table.ToImmutableArray();
     }
 
     private static uint Process(ImmutableArray<uint> table, uint accumulator, ReadOnlySpan<byte> buffer)

Library/DiscUtils.Core/Internal/Utilities.cs

@@ -26,6 +26,7 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.IO;
 using System.Linq;
 using System.Runtime.CompilerServices;
@@ -563,4 +564,12 @@ public static UnixFileType ToUnixFileType(this TarFileType entryType)
     }
 
     #endregion
+
+#if NETFRAMEWORK && !NET462_OR_GREATER
+    public static ImmutableArray<T> ToImmutableArray<T>(this ReadOnlySpan<T> source)
+        => ImmutableArray.Create(source.ToArray());
+
+    public static ImmutableArray<T> ToImmutableArray<T>(this Span<T> source)
+        => ImmutableArray.Create(source.ToArray());
+#endif
 }

Tests/LibraryTests/ThreadSafeStreamTest.cs

@@ -134,14 +134,7 @@ public void Dispose_StopsView()
         var altView = tss.OpenView();
         tss.Dispose();
 
-        try
-        {
-            altView.ReadByte();
-            Assert.Fail("Disposed stream didn't stop view");
-        }
-        catch (ObjectDisposedException)
-        {
-        }
+        Assert.Throws<ObjectDisposedException>(() => altView.ReadByte());
     }
 
     [Fact]