/// <summary>Reads the next chunk from stream.</summary>
/// <returns><c>true</c> if next has been read, or <c>false</c> if it is legitimate end of file.
/// Throws <see cref="EndOfStreamException"/> if end of stream was unexpected.</returns>
private bool AcquireNextChunk()
{
do
{
ulong varint;
if (!TryReadVarInt(out varint))
{
return(false);
}
var flags = (ChunkFlags)varint;
var isCompressed = (flags & ChunkFlags.Compressed) != 0;
var originalLength = (int)ReadVarInt();
var compressedLength = isCompressed ? (int)ReadVarInt() : originalLength;
if (compressedLength > originalLength)
{
throw EndOfStream(); // corrupted
}
if (compressedDataBuffer == null || compressedDataBuffer.Length < compressedLength)
{
compressedDataBuffer = new byte[compressedLength];
}
var chunk = ReadBlock(compressedDataBuffer, 0, compressedLength);
if (chunk != compressedLength)
{
throw EndOfStream(); // currupted
}
if (!isCompressed)
{
// swap the buffers
var oldDataBuffer = dataBuffer;
dataBuffer = compressedDataBuffer; // no compression on this chunk
compressedDataBuffer = oldDataBuffer; // ensure that compressedDataBuffer and dataBuffer are different
bufferLength = compressedLength;
}
else
{
if (dataBuffer == null || dataBuffer.Length < originalLength)
{
dataBuffer = new byte[originalLength];
}
var passes = (int)flags >> 2;
if (passes != 0)
{
throw new NotSupportedException("Chunks with multiple passes are not supported.");
}
LZ4Codec.Decode(compressedDataBuffer, 0, compressedLength, dataBuffer, 0, originalLength, true);
bufferLength = originalLength;
}
bufferOffset = 0;
} while (bufferLength == 0); // skip empty block (shouldn't happen but...)
return(true);
}
/// <summary>Flushes current chunk.</summary>
private void FlushCurrentChunk()
{
if (bufferOffset <= 0)
{
return;
}
var compressed = new byte[bufferOffset];
var compressedLength = highCompression
? LZ4Codec.EncodeHC(dataBuffer, 0, bufferOffset, compressed, 0, bufferOffset)
: LZ4Codec.Encode(dataBuffer, 0, bufferOffset, compressed, 0, bufferOffset);
if (compressedLength <= 0 || compressedLength >= bufferOffset)
{
// uncompressible block
compressed = dataBuffer;
compressedLength = bufferOffset;
}
var isCompressed = compressedLength < bufferOffset;
var flags = ChunkFlags.None;
if (isCompressed)
{
flags |= ChunkFlags.Compressed;
}
if (highCompression)
{
flags |= ChunkFlags.HighCompression;
}
WriteVarInt((ulong)flags);
WriteVarInt((ulong)bufferOffset);
if (isCompressed)
{
WriteVarInt((ulong)compressedLength);
}
innerStream.Write(compressed, 0, compressedLength);
innerStreamPosition += compressedLength;
bufferOffset = 0;
}