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README.md

LZ4 for .NET (C++ /CLI)

LZ4 has been written by Yann Collet and the original sources can be found on https://github.com/lz4/lz4
This project contains the original C sources recompiled for (Pure) CLR

Requirements

This project requires the .NET Framework (3.5 and up are supported)
This project requires the VC++ redistributable

  • .NET 3.5 requires VC++ 2008 redistributable
  • .NET 4.0-4.7.2 requires VC++ 2019 16.3 redistributable

It does not run on .NET Standard or .NET Core

.NET Core

For a managed, .NET Standard 2.0+ version, that does run on .NET Core see
https://github.com/IonKiwi/lz4.managed

How to use

Project contains 3 ways of using the library

non-streaming

Non streaming version, works with managed byte arrays

Example:

  // compress data
  byte[] dataToCompress = ...
  byte[] compressedData = LZ4Helper.Compress(dataToCompress);
  // decompress data
  byte[] decompressedData = LZ4Helper.Decompress(compressedData);

streaming

Streaming version, using the LZ4 Framing Format (v1.6.1).
The compressed data that this stream creates is readable by the lz4 command line tools.

Example:

  // compress data [with content checksum]
  using (LZ4Stream stream = LZ4Stream.CreateCompressor(innerStream, LZ4StreamMode.Write, LZ4FrameBlockMode.Linked, LZ4FrameBlockSize.Max64KB, LZ4FrameChecksumMode.Content, null, false)) {
    // write uncompressed data to the lz4 stream
	// the stream will compress the data and write it to the innerStream
	stream.Write(buffer, 0, buffer.Length);	
  }
  
  // compress data [with block and content checksum, start a new frame after 100 data blocks]
  // note: the lz4 command line tools do NOT support block checksums currently
  using (LZ4Stream stream = LZ4Stream.CreateCompressor(innerStream, LZ4StreamMode.Write, LZ4FrameBlockMode.Linked, LZ4FrameBlockSize.Max64KB, LZ4FrameChecksumMode.Block | LZ4FrameChecksumMode.Content, 100, false)) {
    // write uncompressed data to the lz4 stream
	// the stream will compress the data and write it to the innerStream
	stream.Write(buffer, 0, buffer.Length);	
  }
  
  // decompress data (in read mode)
  using (LZ4Stream stream = LZ4Stream.CreateDecompressor(innerStream, LZ4StreamMode.Read, false)) {
    // the lz4 stream will read the compressed data from the innerStream
    // and return the uncompressed data in 'buffer'
	int bytesRead = stream.Read(buffer, 0, buffer.Length);
  }
  
  // decompress data (in write mode)
  using (LZ4Stream stream = LZ4Stream.CreateDecompressor(innerStream, LZ4StreamMode.Write, false)) {
    // the lz4 stream will decompress the data from 'buffer'
	// and write the uncompressed data to the 'innerStream'
	stream.Write(buffer, 0, buffer.Length);
  }

minimal streaming

Streaming version using a custom minimal frame format.
Based on 'blockStreaming_ringBuffer.c' example from the original lz4 sources.

Compressed data is NOT readable by the lz4 command line tools.

Example:

  // compress data
  using (LZ4MinimalFrameFormatStream stream = new LZ4MinimalFrameFormatStream(tmpFile1, CompressionMode.Compress) {
	// write uncompressed data to the lz4 stream
	// the stream will compress the data and write it to the innerStream
	stream.Write(buffer, 0, buffer.Length);	
  }
  
  // decompress data
  using (LZ4MinimalFrameFormatStream stream = new LZ4MinimalFrameFormatStream(innerStream, CompressionMode.Decompress)) {
    // the lz4 stream will read the compressed data from the innerStream
    // and return the uncompressed data in 'buffer'
	int bytesRead = stream.Read(buffer, 0, buffer.Length)
  }

NOTE:

  • LZ4MinimalFrameFormatStream contains a ctor to specify the size of the ringbuffer, the ringbuffer used for encoding and decoding need to be sychronized, i.e. use the same (ring)buffer sizes for encoding and decoding.
  • Although the frame format of LZ4MinimalFrameFormatStream is shorter, it is probably better to use LZ4Stream as it has more options (like a content checksum) and is readable by the lz4 command line tools.
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