public override void Flush()
{
var maxCompressedSize = LZ4Codec.MaximumOutputLength(_uncompressedBuffer.Length);
if (_compressedBuffer == null || _compressedBuffer.Length < maxCompressedSize)
{
_compressedBuffer = new byte[maxCompressedSize];
}
var compressedSize = LZ4Codec.Encode(_uncompressedBuffer, 0, _bufferLen, _compressedBuffer, 0, _compressedBuffer.Length);
if (compressedSize >= _bufferLen)
{
// Lz4 allows to write non-compressed block.
// Reuse _ncompressedBuffer which is not needed anymore to serialize block size
LittleEndianConverter.Write((uint)(_bufferLen | 1 << 31), _compressedBuffer, 0); // highest bit set indicates no compression
_base.Write(_compressedBuffer, 0, 4);
_base.Write(_uncompressedBuffer, 0, _bufferLen);
}
else
{
LittleEndianConverter.Write((uint)compressedSize, _uncompressedBuffer, 0);
_base.Write(_uncompressedBuffer, 0, 4);
_base.Write(_compressedBuffer, 0, compressedSize);
}
_bufferLen = 0;
}
// TODO: for optimization, hardcode the whole header as static array
static byte[] CreateHeader()
{
var buff = new byte[4 + 3];
LittleEndianConverter.Write(MAGIC, buff, 0);
// Version 1; Block Independence
var flags = 1 << 6 | 1 << 5; //96;
// TODO: make lz4 block size configurable
// Block size 64Kb
var bd = 1 << 6; //64;
buff[4] = (byte)flags;
buff[5] = (byte)bd;
var hasher = new xxHash();
hasher.Init();
hasher.Update(buff, 6);
var checksum = hasher.Digest() >> 8 & 0xff; // 26
buff[6] = (byte)checksum;
return(buff);
}
