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Add LZMA Decompression Support (#11)
* Add lzma decompression support * Fix code quality issues * Fix byte buffer not advancing offset in ReadBytesToSpan * Reduce allocations of compressors when not necessary * Extract decompression to separate class * Dispose of compression streams when done * Fix accessibilty error * Add test * Use try/finally for secondary compressor disposal
1 parent 025dc8f commit f50c8c6

13 files changed

Lines changed: 334 additions & 94 deletions

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‎src/VCDiff.Tests/ExternDiffTests.cs‎

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@@ -20,6 +20,7 @@ public class ExternDiffTests
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[InlineData("sample.xdelta")]
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[InlineData("sample_nosmallstr.xdelta")]
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[InlineData("sample_appheader.xdelta")]
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[InlineData("a-to-b-lzma-compression.xdelta")]
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public async Task ExternTest_ImplAsync(string patchfile)
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{
@@ -53,6 +54,7 @@ public async Task ExternTest_ImplAsync(string patchfile)
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[InlineData("sample.xdelta")]
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[InlineData("sample_nosmallstr.xdelta")]
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[InlineData("sample_appheader.xdelta")]
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[InlineData("a-to-b-lzma-compression.xdelta")]
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public void ExternTest_Impl(string patchfile)
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{

‎src/VCDiff.Tests/patches/a-to-b-lzma-compression.xdelta‎

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‎src/VCDiff/Compressors/ICompressor.cs‎

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using VCDiff.Includes;
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using VCDiff.Shared;
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namespace VCDiff.Compressors
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{
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/// <summary>
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/// A compression method for secondary compression, for use when <see cref="VCDiffCodeFlags.VCDDECOMPRESS"/> is enabled in the header and the appropriate <see cref="VCDiffCompressFlags"/> flag is enabled for the section in the window.
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/// </summary>
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/// <remarks>
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/// Implementations are stateful, and a single instance must be used for the entire file for a single operation (compression or decompression).
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/// </remarks>
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internal interface ICompressor
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{
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PinnedArrayRental Decompress(WindowSectionType windowSectionType, PinnedArrayRental sectionData);
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}
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}

‎src/VCDiff/Compressors/XzCompressor.cs‎

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using SharpCompress.Compressors.Xz;
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using System;
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using System.Collections.Generic;
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using System.IO;
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using System.Text;
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using VCDiff.Shared;
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namespace VCDiff.Compressors
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{
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internal class XzCompressor : ICompressor, IDisposable
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{
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public XzCompressor()
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{
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addRunCompressedBuffer = new();
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instructionsCompressedBuffer = new();
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addressesCompressedBuffer = new();
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addRunDecompressor = new(addRunCompressedBuffer);
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instructionsDecompressor = new(instructionsCompressedBuffer);
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addressesDecompressor = new(addressesCompressedBuffer);
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}
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private readonly MemoryStream addRunCompressedBuffer;
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private readonly MemoryStream instructionsCompressedBuffer;
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private readonly MemoryStream addressesCompressedBuffer;
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private readonly XZStream addRunDecompressor;
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private readonly XZStream instructionsDecompressor;
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private readonly XZStream addressesDecompressor;
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public PinnedArrayRental Decompress(WindowSectionType windowSectionType, PinnedArrayRental sectionData)
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{
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if (sectionData.Data == null)
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{
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throw new ArgumentException("Cannot decompress null data");
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}
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MemoryStream memoryStream;
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XZStream xzStream;
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switch (windowSectionType)
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{
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case WindowSectionType.AddRunData:
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memoryStream = addRunCompressedBuffer;
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xzStream = addRunDecompressor;
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break;
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case WindowSectionType.InstructionsAndSizes:
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memoryStream = instructionsCompressedBuffer;
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xzStream = instructionsDecompressor;
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break;
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case WindowSectionType.AddressForCopy:
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memoryStream = addressesCompressedBuffer;
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xzStream = addressesDecompressor;
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break;
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default:
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throw new ArgumentOutOfRangeException(nameof(windowSectionType));
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}
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var uncompressedLength = VarIntBE.ParseInt32(sectionData.AsSpan(), out int uncompressedLengthByteCount);
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var compressedData = sectionData.AsSpan().Slice(uncompressedLengthByteCount);
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// Each section in a window uses the same compression stream throughout the file
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// If this is not the first window, reuse the same stream from before, just using different data
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memoryStream.SetLength(compressedData.Length);
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memoryStream.Position = 0;
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memoryStream.Write(compressedData);
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memoryStream.Position = 0;
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var decompressedData = new PinnedArrayRental(uncompressedLength);
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xzStream.ReadExactly(decompressedData.AsSpan());
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return decompressedData;
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}
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public void Dispose()
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{
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addressesCompressedBuffer?.Dispose();
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instructionsCompressedBuffer?.Dispose();
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addressesCompressedBuffer?.Dispose();
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addRunDecompressor?.Dispose();
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instructionsDecompressor?.Dispose();
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addressesDecompressor?.Dispose();
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}
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}
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}

‎src/VCDiff/Decoders/BodyDecoder.cs‎

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@@ -2,7 +2,6 @@
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using System.IO;
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using System.Threading;
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using System.Threading.Tasks;
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using Microsoft.IO;
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using VCDiff.Includes;
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using VCDiff.Shared;
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@@ -20,6 +19,7 @@ internal class BodyDecoder<TWindowDecoderByteBuffer, TSourceBuffer, TDeltaBuffer
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private AddressCache addressCache;
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private MemoryStream targetData;
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private CustomCodeTableDecoder? customTable;
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private readonly bool disableChecksums;
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//the total bytes decoded
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public long TotalBytesDecoded { get; private set; }
@@ -32,7 +32,7 @@ internal class BodyDecoder<TWindowDecoderByteBuffer, TSourceBuffer, TDeltaBuffer
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/// <param name="delta">The delta</param>
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/// <param name="decodedTarget">the out stream</param>
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/// <param name="customTable">custom table if any. Default is null.</param>
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public BodyDecoder(WindowDecoder<TWindowDecoderByteBuffer> w, TSourceBuffer source, TDeltaBuffer delta, Stream decodedTarget, CustomCodeTableDecoder? customTable = null)
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public BodyDecoder(WindowDecoder<TWindowDecoderByteBuffer> w, TSourceBuffer source, TDeltaBuffer delta, Stream decodedTarget, CustomCodeTableDecoder? customTable = null, bool disableChecksums = false)
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{
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if (customTable != null)
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{
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this.source = source;
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this.delta = delta;
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this.targetData = Pool.MemoryStreamManager.GetStream(nameof(BodyDecoder<TWindowDecoderByteBuffer, TSourceBuffer, TDeltaBuffer>), (int) w.TargetWindowLength);
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this.disableChecksums = disableChecksums;
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}
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private VCDiffResult DecodeInterleaveCore()
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{
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uint adler = Checksum.ComputeGoogleAdler32(targetData.GetBuffer().AsSpan(0, (int)targetData.Length));
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if (adler != window.Checksum)
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if (adler != window.Checksum && !disableChecksums)
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{
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result = VCDiffResult.ERROR;
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}
@@ -263,7 +264,7 @@ private VCDiffResult DecodeCore()
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{
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uint adler = Checksum.ComputeXdelta3Adler32(targetData.GetBuffer().AsSpan(0, (int)targetData.Length));
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if (adler != window.Checksum)
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if (adler != window.Checksum && !disableChecksums)
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{
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result = VCDiffResult.ERROR;
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}

‎src/VCDiff/Decoders/SharedDecompressors.cs‎

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using SharpCompress.Compressors.Xz;
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using System.IO;
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namespace VCDiff.Decoders
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{
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internal class SharedDecompressors
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{
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public XZStream? AddRunDecompressor;
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public XZStream? InstructionsDecompressor;
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public XZStream? AddressesDecompressor;
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public MemoryStream? AddRunCompressedBuffer;
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public MemoryStream? InstructionsCompressedBuffer;
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public MemoryStream? AddressesCompressedBuffer;
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}
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}

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