diff --git a/src/ICSharpCode.SharpZipLib/Zip/Compression/InflaterDynHeader.cs b/src/ICSharpCode.SharpZipLib/Zip/Compression/InflaterDynHeader.cs
index 8e0196b11..b71f05b2b 100644
--- a/src/ICSharpCode.SharpZipLib/Zip/Compression/InflaterDynHeader.cs
+++ b/src/ICSharpCode.SharpZipLib/Zip/Compression/InflaterDynHeader.cs
@@ -57,7 +57,7 @@ private IEnumerable<bool> CreateStateMachine()
while (!input.TryGetBits(3, ref codeLengths, MetaCodeLengthIndex[i])) yield return false;
}
- var metaCodeTree = new InflaterHuffmanTree(codeLengths);
+ var metaCodeTree = new InflaterHuffmanTree(codeLengths.AsSpan());
// Decompress the meta tree symbols into the data table code lengths
int index = 0;
@@ -113,8 +113,8 @@ private IEnumerable<bool> CreateStateMachine()
if (codeLengths[256] == 0)
throw new StreamDecodingException("Inflater dynamic header end-of-block code missing");
- litLenTree = new InflaterHuffmanTree(new ArraySegment<byte>(codeLengths, 0, litLenCodeCount));
- distTree = new InflaterHuffmanTree(new ArraySegment<byte>(codeLengths, litLenCodeCount, distanceCodeCount));
+ litLenTree = new InflaterHuffmanTree(codeLengths.AsSpan(0, litLenCodeCount));
+ distTree = new InflaterHuffmanTree(codeLengths.AsSpan(litLenCodeCount, distanceCodeCount));
yield return true;
}
diff --git a/src/ICSharpCode.SharpZipLib/Zip/Compression/InflaterHuffmanTree.cs b/src/ICSharpCode.SharpZipLib/Zip/Compression/InflaterHuffmanTree.cs
index ed318824f..e6f2663f4 100644
--- a/src/ICSharpCode.SharpZipLib/Zip/Compression/InflaterHuffmanTree.cs
+++ b/src/ICSharpCode.SharpZipLib/Zip/Compression/InflaterHuffmanTree.cs
@@ -1,6 +1,8 @@
using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
using System;
using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.InteropServices;
namespace ICSharpCode.SharpZipLib.Zip.Compression
{
@@ -13,6 +15,11 @@ public class InflaterHuffmanTree
private const int MAX_BITLEN = 15;
+ // see InflaterHuffmanTreeTest.GenerateTrees how to generate the sequence
+ // stored in DLL's static data section so no allocation occurs
+ private static ReadOnlySpan<byte> defLitLenTreeBytes => new byte[] { 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8 };
+ private static ReadOnlySpan<byte> defDistTreeBytes => new byte[] { 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5 };
+
#endregion Constants
#region Instance Fields
@@ -24,52 +31,41 @@ public class InflaterHuffmanTree
/// <summary>
/// Literal length tree
/// </summary>
- public static InflaterHuffmanTree defLitLenTree;
+ public static readonly InflaterHuffmanTree defLitLenTree = new InflaterHuffmanTree(defLitLenTreeBytes);
/// <summary>
/// Distance tree
/// </summary>
- public static InflaterHuffmanTree defDistTree;
+ public static readonly InflaterHuffmanTree defDistTree = new InflaterHuffmanTree(defDistTreeBytes);
+
+ #region Constructors
- static InflaterHuffmanTree()
+ /// <summary>
+ /// Constructs a Huffman tree from the array of code lengths.
+ /// </summary>
+ /// <param name = "codeLengths">
+ /// the array of code lengths
+ /// </param>
+ public InflaterHuffmanTree(IList<byte> codeLengths) : this(ListToSpan(codeLengths))
{
- try
- {
- byte[] codeLengths = new byte[288];
- int i = 0;
- while (i < 144)
- {
- codeLengths[i++] = 8;
- }
- while (i < 256)
- {
- codeLengths[i++] = 9;
- }
- while (i < 280)
- {
- codeLengths[i++] = 7;
- }
- while (i < 288)
- {
- codeLengths[i++] = 8;
- }
- defLitLenTree = new InflaterHuffmanTree(codeLengths);
+ }
- codeLengths = new byte[32];
- i = 0;
- while (i < 32)
- {
- codeLengths[i++] = 5;
- }
- defDistTree = new InflaterHuffmanTree(codeLengths);
+ private static ReadOnlySpan<byte> ListToSpan(IList<byte> codeLengths)
+ {
+#if NET6_0_OR_GREATER
+ if (codeLengths is List<byte> list)
+ {
+ return CollectionsMarshal.AsSpan(list);
}
- catch (Exception)
+#endif
+ if (codeLengths is byte[] array)
{
- throw new SharpZipBaseException("InflaterHuffmanTree: static tree length illegal");
+ return array;
}
- }
- #region Constructors
+ // slow path
+ return codeLengths.ToArray();
+ }
/// <summary>
/// Constructs a Huffman tree from the array of code lengths.
@@ -77,21 +73,20 @@ static InflaterHuffmanTree()
/// <param name = "codeLengths">
/// the array of code lengths
/// </param>
- public InflaterHuffmanTree(IList<byte> codeLengths)
+ internal InflaterHuffmanTree(ReadOnlySpan<byte> codeLengths)
{
BuildTree(codeLengths);
}
#endregion Constructors
- private void BuildTree(IList<byte> codeLengths)
+ private void BuildTree(ReadOnlySpan<byte> codeLengths)
{
- int[] blCount = new int[MAX_BITLEN + 1];
- int[] nextCode = new int[MAX_BITLEN + 1];
+ Span<int> blCount = stackalloc int[MAX_BITLEN + 1];
+ Span<int> nextCode = stackalloc int[MAX_BITLEN + 1];
- for (int i = 0; i < codeLengths.Count; i++)
+ foreach (var bits in codeLengths)
{
- int bits = codeLengths[i];
if (bits > 0)
{
blCount[bits]++;
@@ -136,20 +131,21 @@ private void BuildTree(IList<byte> codeLengths)
}
}
- for (int i = 0; i < codeLengths.Count; i++)
+ for (var i = 0; i < codeLengths.Length; i++)
{
- int bits = codeLengths[i];
+ var bits = codeLengths[i];
if (bits == 0)
{
continue;
}
+
code = nextCode[bits];
int revcode = DeflaterHuffman.BitReverse(code);
if (bits <= 9)
{
do
{
- tree[revcode] = (short)((i << 4) | bits);
+ tree[revcode] = (short) ((i << 4) | bits);
revcode += 1 << bits;
} while (revcode < 512);
}
@@ -160,10 +156,11 @@ private void BuildTree(IList<byte> codeLengths)
subTree = -(subTree >> 4);
do
{
- tree[subTree | (revcode >> 9)] = (short)((i << 4) | bits);
+ tree[subTree | (revcode >> 9)] = (short) ((i << 4) | bits);
revcode += 1 << bits;
} while (revcode < treeLen);
}
+
nextCode[bits] = code + (1 << (16 - bits));
}
}
diff --git a/src/ICSharpCode.SharpZipLib/Zip/Compression/Streams/OutputWindow.cs b/src/ICSharpCode.SharpZipLib/Zip/Compression/Streams/OutputWindow.cs
index d8241c18c..b3a5a21be 100644
--- a/src/ICSharpCode.SharpZipLib/Zip/Compression/Streams/OutputWindow.cs
+++ b/src/ICSharpCode.SharpZipLib/Zip/Compression/Streams/OutputWindow.cs
@@ -1,4 +1,5 @@
using System;
+using System.Runtime.CompilerServices;
namespace ICSharpCode.SharpZipLib.Zip.Compression.Streams
{
@@ -36,12 +37,18 @@ public void Write(int value)
{
if (windowFilled++ == WindowSize)
{
- throw new InvalidOperationException("Window full");
+ ThrowWindowFull();
}
window[windowEnd++] = (byte)value;
windowEnd &= WindowMask;
}
+ [MethodImpl(MethodImplOptions.NoInlining)]
+ private static void ThrowWindowFull()
+ {
+ throw new InvalidOperationException("Window full");
+ }
+
private void SlowRepeat(int repStart, int length, int distance)
{
while (length-- > 0)
diff --git a/test/ICSharpCode.SharpZipLib.Tests/Zip/InflaterHuffmanTreeTest.cs b/test/ICSharpCode.SharpZipLib.Tests/Zip/InflaterHuffmanTreeTest.cs
new file mode 100644
index 000000000..9a8553f1f
--- /dev/null
+++ b/test/ICSharpCode.SharpZipLib.Tests/Zip/InflaterHuffmanTreeTest.cs
@@ -0,0 +1,51 @@
+using System;
+using NUnit.Framework;
+
+namespace ICSharpCode.SharpZipLib.Tests.Zip
+{
+ public class InflaterHuffmanTreeTest
+ {
+ /// <summary>
+ /// Generates code based on optimization described in https://github.com/dotnet/csharplang/issues/5295#issue-1028421234
+ /// </summary>
+ [Test]
+ [Explicit]
+ public void GenerateTrees()
+ {
+ // generates the byte arrays needed by InflaterHuffmanTree
+ var defLitLenTreeBytes = new byte[288];
+ int i = 0;
+ while (i < 144)
+ {
+ defLitLenTreeBytes[i++] = 8;
+ }
+
+ while (i < 256)
+ {
+ defLitLenTreeBytes[i++] = 9;
+ }
+
+ while (i < 280)
+ {
+ defLitLenTreeBytes[i++] = 7;
+ }
+
+ while (i < 288)
+ {
+ defLitLenTreeBytes[i++] = 8;
+ }
+
+ Console.WriteLine($"private static ReadOnlySpan<byte> defLitLenTreeBytes => new byte[] {{ { string.Join(", ", defLitLenTreeBytes) } }};");
+
+
+ var defDistTreeBytes = new byte[32];
+ i = 0;
+ while (i < 32)
+ {
+ defDistTreeBytes[i++] = 5;
+ }
+
+ Console.WriteLine($"private static ReadOnlySpan<byte> defDistTreeBytes => new byte[] {{ { string.Join(", ", defDistTreeBytes) } }};");
+ }
+ }
+}