Add pure managed LZ4 compression to serializers

Implemented LZ4 compression/decompression in pure managed code, compatible with all platforms including WASM. Added new helpers (`Lz4`, `Lz4Compressor`, `Lz4Decompressor`) and a `Lz4CompressionMode` enum. Updated `AcBinarySerializerOptions` to support compression, and modified all relevant serializer methods to apply LZ4 when enabled. Benchmarks and buffer handling updated to support zero-allocation compression. No native dependencies required.

AyCode.Core.Serializers.Console/Program.cs

@@ -1,13 +1,15 @@
-using System.Diagnostics;
+using AyCode.Core.Compression;
-using System.Runtime.CompilerServices;
-using System.Text;
-using System.Text.Json;
 using AyCode.Core.Serializers.Binaries;
 using AyCode.Core.Serializers.Jsons;
 using AyCode.Core.Tests.TestModels;
 using MessagePack;
 using MessagePack.Resolvers;
+using Microsoft.Extensions.Options;
 using Newtonsoft.Json;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Text;
+using System.Text.Json;
 
 namespace AyCode.Core.Serializers.Console;
 
@@ -486,6 +488,8 @@ public static class Program
             _options = options;
             Name = name;
             _serialized = AcBinarySerializer.Serialize(order, options);
+
+            //_options.UseCompression = Lz4CompressionMode.Block;
         }
 
         public void Warmup(int iterations)
@@ -553,6 +557,7 @@ public static class Program
             _order = order;
             Name = name;
             _options = ContractlessStandardResolver.Options.WithCompression(MessagePackCompression.None);
+            //_options = ContractlessStandardResolver.Options.WithCompression(MessagePackCompression.Lz4Block);
             _serialized = MessagePackSerializer.Serialize(order, _options);
         }
 

AyCode.Core/Compression/Lz4.cs

@@ -0,0 +1,206 @@
+namespace AyCode.Core.Compression;
+
+/// <summary>
+/// High-level LZ4 compression helper. Pure managed implementation that works on all platforms including WASM.
+/// </summary>
+public static class Lz4
+{
+    /// <summary>
+    /// Compresses data using LZ4 Block format.
+    /// </summary>
+    /// <param name="data">Data to compress.</param>
+    /// <returns>Compressed data with 4-byte original size header.</returns>
+    public static byte[] CompressBlock(byte[] data)
+    {
+        ArgumentNullException.ThrowIfNull(data);
+        return CompressBlock(data.AsSpan());
+    }
+
+    /// <summary>
+    /// Compresses data using LZ4 Block format.
+    /// </summary>
+    /// <param name="data">Data to compress.</param>
+    /// <returns>Compressed data with 4-byte original size header.</returns>
+    public static byte[] CompressBlock(ReadOnlySpan<byte> data)
+    {
+        if (data.Length == 0)
+            return [];
+
+        var compressed = Lz4Compressor.Compress(data);
+
+        // Prepend original size (4 bytes, little-endian)
+        var result = new byte[4 + compressed.Length];
+        WriteInt32LittleEndian(result, 0, data.Length);
+        compressed.CopyTo(result.AsSpan(4));
+
+        return result;
+    }
+
+    /// <summary>
+    /// Decompresses LZ4 Block format data.
+    /// </summary>
+    /// <param name="compressedData">Compressed data with 4-byte original size header.</param>
+    /// <returns>Decompressed data.</returns>
+    public static byte[] DecompressBlock(byte[] compressedData)
+    {
+        ArgumentNullException.ThrowIfNull(compressedData);
+        return DecompressBlock(compressedData.AsSpan());
+    }
+
+    /// <summary>
+    /// Decompresses LZ4 Block format data.
+    /// </summary>
+    /// <param name="compressedData">Compressed data with 4-byte original size header.</param>
+    /// <returns>Decompressed data.</returns>
+    public static byte[] DecompressBlock(ReadOnlySpan<byte> compressedData)
+    {
+        if (compressedData.Length < 4)
+            return [];
+
+        var originalSize = ReadInt32LittleEndian(compressedData, 0);
+        if (originalSize <= 0)
+            return [];
+
+        var compressed = compressedData.Slice(4);
+        return Lz4Decompressor.Decompress(compressed, originalSize);
+    }
+
+    /// <summary>
+    /// Compresses data using LZ4 BlockArray format (chunked compression).
+    /// Better for large data and streaming scenarios.
+    /// </summary>
+    /// <param name="data">Data to compress.</param>
+    /// <param name="chunkSize">Size of each chunk (default 64KB).</param>
+    /// <returns>Compressed data with chunk headers.</returns>
+    public static byte[] CompressBlockArray(byte[] data, int chunkSize = Lz4Compressor.DefaultChunkSize)
+    {
+        ArgumentNullException.ThrowIfNull(data);
+        return CompressBlockArray(data.AsSpan(), chunkSize);
+    }
+
+    /// <summary>
+    /// Compresses data using LZ4 BlockArray format (chunked compression).
+    /// Better for large data and streaming scenarios.
+    /// </summary>
+    /// <param name="data">Data to compress.</param>
+    /// <param name="chunkSize">Size of each chunk (default 64KB).</param>
+    /// <returns>Compressed data with chunk headers.</returns>
+    public static byte[] CompressBlockArray(ReadOnlySpan<byte> data, int chunkSize = Lz4Compressor.DefaultChunkSize)
+    {
+        if (data.Length == 0)
+            return [];
+
+        return Lz4Compressor.CompressBlockArray(data, chunkSize);
+    }
+
+    /// <summary>
+    /// Decompresses LZ4 BlockArray format data.
+    /// </summary>
+    /// <param name="compressedData">Compressed data with chunk headers.</param>
+    /// <returns>Decompressed data.</returns>
+    public static byte[] DecompressBlockArray(byte[] compressedData)
+    {
+        ArgumentNullException.ThrowIfNull(compressedData);
+        return DecompressBlockArray(compressedData.AsSpan());
+    }
+
+    /// <summary>
+    /// Decompresses LZ4 BlockArray format data.
+    /// </summary>
+    /// <param name="compressedData">Compressed data with chunk headers.</param>
+    /// <returns>Decompressed data.</returns>
+    public static byte[] DecompressBlockArray(ReadOnlySpan<byte> compressedData)
+    {
+        if (compressedData.Length < 4)
+            return [];
+
+        return Lz4Decompressor.DecompressBlockArray(compressedData);
+    }
+
+    /// <summary>
+    /// Compresses data using the specified compression mode.
+    /// </summary>
+    /// <param name="data">Data to compress.</param>
+    /// <param name="mode">Compression mode.</param>
+    /// <returns>Compressed data.</returns>
+    public static byte[] Compress(byte[] data, Lz4CompressionMode mode)
+    {
+        return mode switch
+        {
+            Lz4CompressionMode.None => data,
+            Lz4CompressionMode.Block => CompressBlock(data),
+            Lz4CompressionMode.BlockArray => CompressBlockArray(data),
+            _ => throw new ArgumentOutOfRangeException(nameof(mode), mode, "Invalid compression mode.")
+        };
+    }
+
+    /// <summary>
+    /// Compresses data using the specified compression mode.
+    /// </summary>
+    /// <param name="data">Data to compress.</param>
+    /// <param name="mode">Compression mode.</param>
+    /// <returns>Compressed data.</returns>
+    public static byte[] Compress(ReadOnlySpan<byte> data, Lz4CompressionMode mode)
+    {
+        return mode switch
+        {
+            Lz4CompressionMode.None => data.ToArray(),
+            Lz4CompressionMode.Block => CompressBlock(data),
+            Lz4CompressionMode.BlockArray => CompressBlockArray(data),
+            _ => throw new ArgumentOutOfRangeException(nameof(mode), mode, "Invalid compression mode.")
+        };
+    }
+
+    /// <summary>
+    /// Decompresses data using the specified compression mode.
+    /// </summary>
+    /// <param name="compressedData">Compressed data.</param>
+    /// <param name="mode">Compression mode used during compression.</param>
+    /// <returns>Decompressed data.</returns>
+    public static byte[] Decompress(byte[] compressedData, Lz4CompressionMode mode)
+    {
+        return mode switch
+        {
+            Lz4CompressionMode.None => compressedData,
+            Lz4CompressionMode.Block => DecompressBlock(compressedData),
+            Lz4CompressionMode.BlockArray => DecompressBlockArray(compressedData),
+            _ => throw new ArgumentOutOfRangeException(nameof(mode), mode, "Invalid compression mode.")
+        };
+    }
+
+    /// <summary>
+    /// Decompresses data using the specified compression mode.
+    /// </summary>
+    /// <param name="compressedData">Compressed data.</param>
+    /// <param name="mode">Compression mode used during compression.</param>
+    /// <returns>Decompressed data.</returns>
+    public static byte[] Decompress(ReadOnlySpan<byte> compressedData, Lz4CompressionMode mode)
+    {
+        return mode switch
+        {
+            Lz4CompressionMode.None => compressedData.ToArray(),
+            Lz4CompressionMode.Block => DecompressBlock(compressedData),
+            Lz4CompressionMode.BlockArray => DecompressBlockArray(compressedData),
+            _ => throw new ArgumentOutOfRangeException(nameof(mode), mode, "Invalid compression mode.")
+        };
+    }
+
+    /// <summary>
+    /// Gets the maximum compressed length for a given input length.
+    /// </summary>
+    public static int GetMaxCompressedLength(int inputLength)
+        => Lz4Compressor.GetMaxCompressedLength(inputLength);
+
+    private static void WriteInt32LittleEndian(byte[] buffer, int offset, int value)
+    {
+        buffer[offset] = (byte)value;
+        buffer[offset + 1] = (byte)(value >> 8);
+        buffer[offset + 2] = (byte)(value >> 16);
+        buffer[offset + 3] = (byte)(value >> 24);
+    }
+
+    private static int ReadInt32LittleEndian(ReadOnlySpan<byte> buffer, int offset)
+    {
+        return buffer[offset] | (buffer[offset + 1] << 8) | (buffer[offset + 2] << 16) | (buffer[offset + 3] << 24);
+    }
+}

AyCode.Core/Compression/Lz4CompressionMode.cs

@@ -0,0 +1,24 @@
+namespace AyCode.Core.Compression;
+
+/// <summary>
+/// LZ4 compression mode.
+/// </summary>
+public enum Lz4CompressionMode
+{
+    /// <summary>
+    /// No compression.
+    /// </summary>
+    None = 0,
+
+    /// <summary>
+    /// LZ4 block compression. Compresses entire payload as single block.
+    /// Better compression ratio, requires full buffer in memory.
+    /// </summary>
+    Block = 1,
+
+    /// <summary>
+    /// LZ4 block array compression. Compresses in 64KB chunks.
+    /// Slightly worse compression ratio, but streaming-friendly and lower memory usage.
+    /// </summary>
+    BlockArray = 2
+}

AyCode.Core/Compression/Lz4Compressor.cs

@@ -0,0 +1,372 @@
+using System.Buffers;
+using System.Runtime.CompilerServices;
+
+namespace AyCode.Core.Compression;
+
+/// <summary>
+/// Pure managed LZ4 compressor. Works on all platforms including WASM.
+/// Implements LZ4 block format compression.
+/// </summary>
+public static class Lz4Compressor
+{
+    private const int HashLog = 12;
+    private const int HashTableSize = 1 << HashLog;
+    private const int MinMatch = 4;
+    private const int MaxInputSize = 0x7E000000; // ~2GB
+    private const int MFLimit = 12; // Minimum match finding limit from end
+    private const int LastLiterals = 5; // Last literals that cannot be matched
+    private const int MatchLengthBits = 4;
+    private const int LiteralLengthBits = 4;
+    private const int RunMask = (1 << LiteralLengthBits) - 1;
+    private const int MatchMask = (1 << MatchLengthBits) - 1;
+
+    /// <summary>
+    /// Default chunk size for BlockArray mode (64KB).
+    /// </summary>
+    public const int DefaultChunkSize = 64 * 1024;
+
+    /// <summary>
+    /// Compresses data using LZ4 block format.
+    /// </summary>
+    /// <param name="source">Source data to compress.</param>
+    /// <returns>Compressed data.</returns>
+    public static byte[] Compress(ReadOnlySpan<byte> source)
+    {
+        if (source.Length == 0)
+            return [];
+
+        if (source.Length > MaxInputSize)
+            throw new ArgumentException($"Input too large. Maximum size is {MaxInputSize} bytes.", nameof(source));
+
+        var maxOutputSize = GetMaxCompressedLength(source.Length);
+        var output = new byte[maxOutputSize];
+        var compressedLength = CompressCore(source, output);
+
+        if (compressedLength == output.Length)
+            return output;
+
+        var result = new byte[compressedLength];
+        output.AsSpan(0, compressedLength).CopyTo(result);
+        return result;
+    }
+
+    /// <summary>
+    /// Compresses data using LZ4 block format into the destination buffer.
+    /// </summary>
+    /// <param name="source">Source data to compress.</param>
+    /// <param name="destination">Destination buffer for compressed data.</param>
+    /// <returns>Number of bytes written to destination.</returns>
+    public static int Compress(ReadOnlySpan<byte> source, Span<byte> destination)
+    {
+        if (source.Length == 0)
+            return 0;
+
+        if (source.Length > MaxInputSize)
+            throw new ArgumentException($"Input too large. Maximum size is {MaxInputSize} bytes.", nameof(source));
+
+        var maxOutputSize = GetMaxCompressedLength(source.Length);
+        if (destination.Length < maxOutputSize)
+            throw new ArgumentException($"Destination buffer too small. Need at least {maxOutputSize} bytes.", nameof(destination));
+
+        return CompressCore(source, destination);
+    }
+
+    /// <summary>
+    /// Compresses data using LZ4 BlockArray format (chunked compression).
+    /// </summary>
+    /// <param name="source">Source data to compress.</param>
+    /// <param name="chunkSize">Size of each chunk (default 64KB).</param>
+    /// <returns>Compressed data with chunk headers.</returns>
+    public static byte[] CompressBlockArray(ReadOnlySpan<byte> source, int chunkSize = DefaultChunkSize)
+    {
+        if (source.Length == 0)
+            return [];
+
+        if (chunkSize < 1024)
+            throw new ArgumentException("Chunk size must be at least 1024 bytes.", nameof(chunkSize));
+
+        var numChunks = (source.Length + chunkSize - 1) / chunkSize;
+        var maxOutputSize = 4 + (numChunks * (8 + GetMaxCompressedLength(chunkSize))); // 4 bytes for total chunks
+
+        using var output = new ArrayPoolWriter(maxOutputSize);
+
+        // Write number of chunks
+        output.WriteInt32LittleEndian(numChunks);
+
+        var offset = 0;
+        while (offset < source.Length)
+        {
+            var remaining = source.Length - offset;
+            var currentChunkSize = Math.Min(remaining, chunkSize);
+            var chunk = source.Slice(offset, currentChunkSize);
+
+            var compressedChunk = Compress(chunk);
+
+            // Write original size
+            output.WriteInt32LittleEndian(currentChunkSize);
+            // Write compressed size
+            output.WriteInt32LittleEndian(compressedChunk.Length);
+            // Write compressed data
+            output.Write(compressedChunk);
+
+            offset += currentChunkSize;
+        }
+
+        return output.ToArray();
+    }
+
+    /// <summary>
+    /// Gets the maximum compressed length for a given input length.
+    /// </summary>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static int GetMaxCompressedLength(int inputLength)
+    {
+        // LZ4 worst case: input + (input / 255) + 16
+        return inputLength + (inputLength / 255) + 16;
+    }
+
+    private static int CompressCore(ReadOnlySpan<byte> source, Span<byte> destination)
+    {
+        var hashTable = ArrayPool<int>.Shared.Rent(HashTableSize);
+        try
+        {
+            Array.Fill(hashTable, -1, 0, HashTableSize);
+            return CompressInternal(source, destination, hashTable);
+        }
+        finally
+        {
+            ArrayPool<int>.Shared.Return(hashTable);
+        }
+    }
+
+    private static int CompressInternal(ReadOnlySpan<byte> source, Span<byte> destination, int[] hashTable)
+    {
+        var srcLength = source.Length;
+        if (srcLength < MFLimit)
+        {
+            // Too small, just store as literals
+            return StoreLiterals(source, destination);
+        }
+
+        var srcIndex = 0;
+        var dstIndex = 0;
+        var anchor = 0;
+        var srcEnd = srcLength;
+        var mfLimit = srcEnd - MFLimit;
+        var matchLimit = srcEnd - LastLiterals;
+
+        // First byte is always literal
+        srcIndex++;
+
+        while (srcIndex < mfLimit)
+        {
+            // Find match
+            var hash = GetHash(source, srcIndex);
+            var matchIndex = hashTable[hash];
+            hashTable[hash] = srcIndex;
+
+            // Check if we have a valid match
+            if (matchIndex >= 0 &&
+                srcIndex - matchIndex <= 65535 &&
+                matchIndex >= anchor &&
+                ReadUInt32(source, matchIndex) == ReadUInt32(source, srcIndex))
+            {
+                // Encode literals before match
+                var literalLength = srcIndex - anchor;
+
+                // Calculate offset BEFORE extending the match
+                var offset = srcIndex - matchIndex;
+
+                // Find match length (extend the match)
+                var matchStart = srcIndex;
+                var refIndex = matchIndex;
+                
+                // Skip the 4 bytes we already matched
+                srcIndex += MinMatch;
+                refIndex += MinMatch;
+
+                // Extend the match
+                while (srcIndex < matchLimit && source[srcIndex] == source[refIndex])
+                {
+                    srcIndex++;
+                    refIndex++;
+                }
+
+                var matchLength = srcIndex - matchStart - MinMatch;
+
+                // Encode token
+                dstIndex = EncodeSequence(destination, dstIndex, source.Slice(anchor, literalLength), offset, matchLength);
+
+                anchor = srcIndex;
+            }
+            else
+            {
+                srcIndex++;
+            }
+        }
+
+        // Encode remaining literals
+        var lastLiterals = srcEnd - anchor;
+        if (lastLiterals > 0)
+        {
+            dstIndex = EncodeLiteralsOnly(destination, dstIndex, source.Slice(anchor, lastLiterals));
+        }
+
+        return dstIndex;
+    }
+
+    private static int StoreLiterals(ReadOnlySpan<byte> source, Span<byte> destination)
+    {
+        return EncodeLiteralsOnly(destination, 0, source);
+    }
+
+    private static int EncodeSequence(Span<byte> dst, int dstIndex, ReadOnlySpan<byte> literals, int offset, int matchLength)
+    {
+        var literalLength = literals.Length;
+
+        // Encode token
+        var token = dstIndex++;
+
+        // Encode literal length
+        if (literalLength >= RunMask)
+        {
+            dst[token] = (byte)(RunMask << MatchLengthBits);
+            var remaining = literalLength - RunMask;
+            while (remaining >= 255)
+            {
+                dst[dstIndex++] = 255;
+                remaining -= 255;
+            }
+            dst[dstIndex++] = (byte)remaining;
+        }
+        else
+        {
+            dst[token] = (byte)(literalLength << MatchLengthBits);
+        }
+
+        // Copy literals
+        literals.CopyTo(dst.Slice(dstIndex));
+        dstIndex += literalLength;
+
+        // Encode offset (little-endian)
+        dst[dstIndex++] = (byte)offset;
+        dst[dstIndex++] = (byte)(offset >> 8);
+
+        // Encode match length
+        if (matchLength >= MatchMask)
+        {
+            dst[token] |= MatchMask;
+            var remaining = matchLength - MatchMask;
+            while (remaining >= 255)
+            {
+                dst[dstIndex++] = 255;
+                remaining -= 255;
+            }
+            dst[dstIndex++] = (byte)remaining;
+        }
+        else
+        {
+            dst[token] |= (byte)matchLength;
+        }
+
+        return dstIndex;
+    }
+
+    private static int EncodeLiteralsOnly(Span<byte> dst, int dstIndex, ReadOnlySpan<byte> literals)
+    {
+        var literalLength = literals.Length;
+
+        // Encode token (no match)
+        var token = dstIndex++;
+
+        // Encode literal length
+        if (literalLength >= RunMask)
+        {
+            dst[token] = (byte)(RunMask << MatchLengthBits);
+            var remaining = literalLength - RunMask;
+            while (remaining >= 255)
+            {
+                dst[dstIndex++] = 255;
+                remaining -= 255;
+            }
+            dst[dstIndex++] = (byte)remaining;
+        }
+        else
+        {
+            dst[token] = (byte)(literalLength << MatchLengthBits);
+        }
+
+        // Copy literals
+        literals.CopyTo(dst.Slice(dstIndex));
+        dstIndex += literalLength;
+
+        return dstIndex;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static int GetHash(ReadOnlySpan<byte> data, int index)
+    {
+        var value = ReadUInt32(data, index);
+        return (int)((value * 2654435761u) >> (32 - HashLog));
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static uint ReadUInt32(ReadOnlySpan<byte> data, int index)
+    {
+        return (uint)(data[index] | (data[index + 1] << 8) | (data[index + 2] << 16) | (data[index + 3] << 24));
+    }
+
+    /// <summary>
+    /// Helper class for writing to a pooled array.
+    /// </summary>
+    private sealed class ArrayPoolWriter : IDisposable
+    {
+        private byte[] _buffer;
+        private int _position;
+
+        public ArrayPoolWriter(int initialCapacity)
+        {
+            _buffer = ArrayPool<byte>.Shared.Rent(initialCapacity);
+            _position = 0;
+        }
+
+        public void WriteInt32LittleEndian(int value)
+        {
+            EnsureCapacity(4);
+            _buffer[_position++] = (byte)value;
+            _buffer[_position++] = (byte)(value >> 8);
+            _buffer[_position++] = (byte)(value >> 16);
+            _buffer[_position++] = (byte)(value >> 24);
+        }
+
+        public void Write(ReadOnlySpan<byte> data)
+        {
+            EnsureCapacity(data.Length);
+            data.CopyTo(_buffer.AsSpan(_position));
+            _position += data.Length;
+        }
+
+        private void EnsureCapacity(int additionalBytes)
+        {
+            if (_position + additionalBytes > _buffer.Length)
+            {
+                var newBuffer = ArrayPool<byte>.Shared.Rent(_buffer.Length * 2);
+                _buffer.AsSpan(0, _position).CopyTo(newBuffer);
+                ArrayPool<byte>.Shared.Return(_buffer);
+                _buffer = newBuffer;
+            }
+        }
+
+        public byte[] ToArray()
+        {
+            var result = new byte[_position];
+            _buffer.AsSpan(0, _position).CopyTo(result);
+            return result;
+        }
+
+        public void Dispose()
+        {
+            ArrayPool<byte>.Shared.Return(_buffer);
+        }
+    }
+}

AyCode.Core/Compression/Lz4Decompressor.cs

@@ -0,0 +1,245 @@
+using System.Buffers;
+using System.Runtime.CompilerServices;
+
+namespace AyCode.Core.Compression;
+
+/// <summary>
+/// Pure managed LZ4 decompressor. Works on all platforms including WASM.
+/// Implements LZ4 block format decompression.
+/// </summary>
+public static class Lz4Decompressor
+{
+    private const int MinMatch = 4;
+    private const int MatchLengthBits = 4;
+    private const int LiteralLengthBits = 4;
+    private const int RunMask = (1 << LiteralLengthBits) - 1;
+    private const int MatchMask = (1 << MatchLengthBits) - 1;
+
+    /// <summary>
+    /// Decompresses LZ4 block format data.
+    /// </summary>
+    /// <param name="source">Compressed data.</param>
+    /// <param name="originalSize">Expected size of decompressed data.</param>
+    /// <returns>Decompressed data.</returns>
+    public static byte[] Decompress(ReadOnlySpan<byte> source, int originalSize)
+    {
+        if (source.Length == 0)
+            return [];
+
+        if (originalSize <= 0)
+            throw new ArgumentException("Original size must be positive.", nameof(originalSize));
+
+        var output = new byte[originalSize];
+        var decompressedLength = DecompressCore(source, output);
+
+        if (decompressedLength != originalSize)
+            throw new InvalidDataException($"Decompressed size mismatch. Expected {originalSize}, got {decompressedLength}.");
+
+        return output;
+    }
+
+    /// <summary>
+    /// Decompresses LZ4 block format data into destination buffer.
+    /// </summary>
+    /// <param name="source">Compressed data.</param>
+    /// <param name="destination">Destination buffer for decompressed data.</param>
+    /// <returns>Number of bytes written to destination.</returns>
+    public static int Decompress(ReadOnlySpan<byte> source, Span<byte> destination)
+    {
+        if (source.Length == 0)
+            return 0;
+
+        return DecompressCore(source, destination);
+    }
+
+    /// <summary>
+    /// Decompresses LZ4 BlockArray format data (chunked compression).
+    /// </summary>
+    /// <param name="source">Compressed data with chunk headers.</param>
+    /// <returns>Decompressed data.</returns>
+    public static byte[] DecompressBlockArray(ReadOnlySpan<byte> source)
+    {
+        if (source.Length < 4)
+            return [];
+
+        var srcIndex = 0;
+
+        // Read number of chunks
+        var numChunks = ReadInt32LittleEndian(source, srcIndex);
+        srcIndex += 4;
+
+        if (numChunks <= 0)
+            return [];
+
+        // Calculate total output size
+        var totalOriginalSize = 0;
+        var tempIndex = srcIndex;
+        for (var i = 0; i < numChunks; i++)
+        {
+            if (tempIndex + 8 > source.Length)
+                throw new InvalidDataException("Invalid BlockArray format: truncated header.");
+
+            var originalChunkSize = ReadInt32LittleEndian(source, tempIndex);
+            var compressedChunkSize = ReadInt32LittleEndian(source, tempIndex + 4);
+            totalOriginalSize += originalChunkSize;
+            tempIndex += 8 + compressedChunkSize;
+        }
+
+        var output = new byte[totalOriginalSize];
+        var outputIndex = 0;
+
+        // Decompress each chunk
+        for (var i = 0; i < numChunks; i++)
+        {
+            var originalChunkSize = ReadInt32LittleEndian(source, srcIndex);
+            srcIndex += 4;
+
+            var compressedChunkSize = ReadInt32LittleEndian(source, srcIndex);
+            srcIndex += 4;
+
+            var compressedChunk = source.Slice(srcIndex, compressedChunkSize);
+            var decompressedLength = DecompressCore(compressedChunk, output.AsSpan(outputIndex, originalChunkSize));
+
+            if (decompressedLength != originalChunkSize)
+                throw new InvalidDataException($"Chunk decompression failed. Expected {originalChunkSize}, got {decompressedLength}.");
+
+            outputIndex += originalChunkSize;
+            srcIndex += compressedChunkSize;
+        }
+
+        return output;
+    }
+
+    /// <summary>
+    /// Tries to decompress LZ4 block format data.
+    /// </summary>
+    /// <param name="source">Compressed data.</param>
+    /// <param name="destination">Destination buffer for decompressed data.</param>
+    /// <param name="bytesWritten">Number of bytes written to destination.</param>
+    /// <returns>True if decompression succeeded, false otherwise.</returns>
+    public static bool TryDecompress(ReadOnlySpan<byte> source, Span<byte> destination, out int bytesWritten)
+    {
+        bytesWritten = 0;
+
+        if (source.Length == 0)
+            return true;
+
+        try
+        {
+            bytesWritten = DecompressCore(source, destination);
+            return true;
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
+    private static int DecompressCore(ReadOnlySpan<byte> source, Span<byte> destination)
+    {
+        var srcIndex = 0;
+        var dstIndex = 0;
+        var srcLength = source.Length;
+        var dstLength = destination.Length;
+
+        while (srcIndex < srcLength)
+        {
+            // Read token
+            var token = source[srcIndex++];
+
+            // Decode literal length
+            var literalLength = token >> MatchLengthBits;
+            if (literalLength == RunMask)
+            {
+                int additionalLength;
+                do
+                {
+                    if (srcIndex >= srcLength)
+                        throw new InvalidDataException("Unexpected end of input while reading literal length.");
+                    additionalLength = source[srcIndex++];
+                    literalLength += additionalLength;
+                } while (additionalLength == 255);
+            }
+
+            // Copy literals
+            if (literalLength > 0)
+            {
+                if (srcIndex + literalLength > srcLength)
+                    throw new InvalidDataException("Unexpected end of input while reading literals.");
+                if (dstIndex + literalLength > dstLength)
+                    throw new InvalidDataException("Output buffer overflow while writing literals.");
+
+                source.Slice(srcIndex, literalLength).CopyTo(destination.Slice(dstIndex));
+                srcIndex += literalLength;
+                dstIndex += literalLength;
+            }
+
+            // Check if we're at the end (no match after last literals)
+            if (srcIndex >= srcLength)
+                break;
+
+            // Decode offset
+            if (srcIndex + 2 > srcLength)
+                throw new InvalidDataException("Unexpected end of input while reading offset.");
+
+            var offset = source[srcIndex] | (source[srcIndex + 1] << 8);
+            srcIndex += 2;
+
+            if (offset == 0)
+                throw new InvalidDataException("Invalid offset: 0.");
+
+            // Decode match length
+            var matchLength = (token & MatchMask) + MinMatch;
+            if ((token & MatchMask) == MatchMask)
+            {
+                int additionalLength;
+                do
+                {
+                    if (srcIndex >= srcLength)
+                        throw new InvalidDataException("Unexpected end of input while reading match length.");
+                    additionalLength = source[srcIndex++];
+                    matchLength += additionalLength;
+                } while (additionalLength == 255);
+            }
+
+            // Copy match
+            var matchStart = dstIndex - offset;
+            if (matchStart < 0)
+                throw new InvalidDataException($"Invalid match offset: {offset} at position {dstIndex}.");
+            if (dstIndex + matchLength > dstLength)
+                throw new InvalidDataException("Output buffer overflow while writing match.");
+
+            // Handle overlapping copy
+            CopyMatch(destination, dstIndex, matchStart, matchLength);
+            dstIndex += matchLength;
+        }
+
+        return dstIndex;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static void CopyMatch(Span<byte> buffer, int dstIndex, int matchStart, int matchLength)
+    {
+        var offset = dstIndex - matchStart;
+
+        // For non-overlapping copies, use fast path
+        if (offset >= matchLength)
+        {
+            buffer.Slice(matchStart, matchLength).CopyTo(buffer.Slice(dstIndex));
+            return;
+        }
+
+        // Overlapping copy - must copy byte by byte
+        // This handles the case where we're copying from recently written data
+        for (var i = 0; i < matchLength; i++)
+        {
+            buffer[dstIndex + i] = buffer[matchStart + i];
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static int ReadInt32LittleEndian(ReadOnlySpan<byte> data, int index)
+    {
+        return data[index] | (data[index + 1] << 8) | (data[index + 2] << 16) | (data[index + 3] << 24);
+    }
+}

AyCode.Core/Serializers/Binaries/AcBinarySerializer.BinarySerializationContext.cs

@@ -464,6 +464,13 @@ public static partial class AcBinarySerializer
 
         #region Output
 
+        /// <summary>
+        /// Returns the serialized data as a ReadOnlySpan without allocation.
+        /// Use this for compression or other processing before final ToArray().
+        /// </summary>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public ReadOnlySpan<byte> AsSpan() => _buffer.AsSpan(0, _position);
+
         public byte[] ToArray()
         {
             var result = GC.AllocateUninitializedArray<byte>(_position);

AyCode.Core/Serializers/Binaries/AcBinarySerializer.cs

@@ -1,4 +1,5 @@
-using AyCode.Core.Helpers;
+using AyCode.Core.Compression;
+using AyCode.Core.Helpers;
 using AyCode.Core.Serializers.Expressions;
 using System.Buffers;
 using System.Collections;
@@ -248,6 +249,13 @@ public static partial class AcBinarySerializer
         var context = SerializeCore(actualValue, runtimeType, options);
         try
         {
+            // Apply compression if enabled - compress directly from buffer span (1 allocation)
+            if (options.UseCompression != Lz4CompressionMode.None)
+            {
+                return Lz4.Compress(context.AsSpan(), options.UseCompression);
+            }
+            
+            // No compression - single allocation for result
             return context.ToArray();
         }
         finally
@@ -260,6 +268,7 @@ public static partial class AcBinarySerializer
     /// <summary>
     /// Serialize object to an IBufferWriter for zero-copy scenarios.
     /// This avoids the final ToArray() allocation by writing directly to the caller's buffer.
+    /// Note: Compression is applied if enabled in options.
     /// </summary>
     public static void Serialize<T>(T value, IBufferWriter<byte> writer, AcBinarySerializerOptions options)
     {
@@ -290,7 +299,18 @@ public static partial class AcBinarySerializer
         var context = SerializeCore(actualValue, runtimeType, options);
         try
         {
-            context.WriteTo(writer);
+            // Apply compression if enabled - compress directly from buffer span (1 allocation)
+            if (options.UseCompression != Lz4CompressionMode.None)
+            {
+                var compressed = Lz4.Compress(context.AsSpan(), options.UseCompression);
+                var destSpan = writer.GetSpan(compressed.Length);
+                compressed.CopyTo(destSpan);
+                writer.Advance(compressed.Length);
+            }
+            else
+            {
+                context.WriteTo(writer);
+            }
         }
         finally
         {
@@ -323,6 +343,7 @@ public static partial class AcBinarySerializer
     /// <summary>
     /// Serialize object and keep the pooled buffer for zero-copy consumers.
     /// Caller must dispose the returned result to release the buffer.
+    /// Note: Compression is applied if enabled in options, result will be immutable (not pooled).
     /// </summary>
     public static BinarySerializationResult SerializeToPooledBuffer<T>(T value, AcBinarySerializerOptions options)
     {
@@ -335,6 +356,13 @@ public static partial class AcBinarySerializer
         var context = SerializeCore(value, runtimeType, options);
         try
         {
+            // If compression enabled, compress directly from buffer span (1 allocation)
+            if (options.UseCompression != Lz4CompressionMode.None)
+            {
+                var compressed = Lz4.Compress(context.AsSpan(), options.UseCompression);
+                return BinarySerializationResult.FromImmutable(compressed);
+            }
+            
             return context.DetachResult();
         }
         finally

AyCode.Core/Serializers/Binaries/AcBinarySerializerOptions.cs

@@ -1,4 +1,5 @@
 using System.Runtime.CompilerServices;
+using AyCode.Core.Compression;
 
 namespace AyCode.Core.Serializers.Binaries;
 
@@ -135,6 +136,16 @@ public sealed class AcBinarySerializerOptions : AcSerializerOptions
     /// </summary>
     public bool RemoveOrphanedItems { get; init; } = false;
 
+    /// <summary>
+    /// Controls LZ4 compression for serialized data.
+    /// None: No compression (default, fastest).
+    /// Block: Compresses entire payload as single block (better compression ratio).
+    /// BlockArray: Compresses in 64KB chunks (streaming-friendly, lower memory).
+    /// Note: Both modes are WASM-compatible (pure managed implementation).
+    /// Default: None
+    /// </summary>
+    public Lz4CompressionMode UseCompression { get; set; } = Lz4CompressionMode.None;
+
     /// <summary>
     /// Creates options with specified max depth.
     /// </summary>