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Revert default buffer to 80KB; add ZStandard minimumRewindBufferSize (DStreamInSize=131075)

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Co-authored-by: adamhathcock <527620+adamhathcock@users.noreply.github.com>
This commit is contained in:
copilot-swe-agent[bot]
2026-04-01 13:12:49 +00:00
committed by GitHub
parent d278cfbf4f
commit 456a7dfd58
3 changed files with 24 additions and 5 deletions
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10
src/SharpCompress/Common/Constants.cs
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@@ -22,9 +22,11 @@ public static class Constants
/// by rewinding and re-reading the same data.
/// </para>
/// <para>
/// <b>Default:</b> 163840 bytes (160KB) - sized to cover ZStandard's worst-case
/// first block on a tar archive (~131KB including frame header overhead).
/// ZStandard blocks can be up to 128KB, exceeding the previous 81KB default.
/// <b>Default:</b> 81920 bytes (80KB) — sufficient for most formats.
/// Formats that require larger buffers (e.g. BZip2, ZStandard) declare their
/// own minimum via <c>TarWrapper.MinimumRewindBufferSize</c>, and
/// <c>TarWrapper.MaximumRewindBufferSize</c> is used at stream construction
/// to ensure the correct capacity is allocated upfront.
/// </para>
/// <para>
/// <b>Typical usage:</b> 500-1000 bytes for most archives
@@ -41,7 +43,7 @@ public static class Constants
/// </list>
/// </para>
/// </remarks>
public static int RewindableBufferSize { get; set; } = 163840;
public static int RewindableBufferSize { get; set; } = 81920;
public static CultureInfo DefaultCultureInfo { get; set; } = CultureInfo.InvariantCulture;
}

13
src/SharpCompress/Compressors/ZStandard/ZstandardConstants.cs
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@@ -6,4 +6,17 @@ internal class ZstandardConstants
/// Magic number found at start of ZStandard frame: 0xFD 0x2F 0xB5 0x28
/// </summary>
public const uint MAGIC = 0xFD2FB528;
/// <summary>
/// Maximum uncompressed size of a single ZStandard block: ZSTD_BLOCKSIZE_MAX = 128 KB.
/// </summary>
public const int BlockSizeMax = 1 << 17; // 131072 bytes
/// <summary>
/// Recommended input (compressed) buffer size for streaming decompression:
/// ZSTD_DStreamInSize = ZSTD_BLOCKSIZE_MAX + ZSTD_blockHeaderSize (3 bytes).
/// The ring buffer must be at least this large to hold the compressed bytes read
/// during format detection before the first rewind.
/// </summary>
public const int DStreamInSize = BlockSizeMax + 3;
}

6
src/SharpCompress/Factories/TarWrapper.cs
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@@ -88,7 +88,11 @@ public class TarWrapper(
ZStandardStream.IsZStandardAsync,
(stream) => new ZStandardStream(stream),
(stream, _) => new ValueTask<Stream>(new ZStandardStream(stream)),
["tar.zst", "tar.zstd", "tzst", "tzstd"]
["tar.zst", "tar.zstd", "tzst", "tzstd"],
// ZStandard decompresses in blocks; the compressed size of the first block
// can be up to ZSTD_BLOCKSIZE_MAX + ZSTD_blockHeaderSize = 131075 bytes.
// The ring buffer must hold all compressed bytes read during format detection.
minimumRewindBufferSize: ZstandardConstants.DStreamInSize
),
new(
CompressionType.LZip,