private static (int Read, bool StreamIsEnd, GzipBuffer gzipBuffer) ReadGzipBufferFromStream(RewindableReadonlyStream stream, byte[] currentBuffer)
{
GzipBuffer gzipBuffer = default;
var(readBuffer, endOfStream) = stream.ReadExactBuffer(currentBuffer);
if (readBuffer.Count > 0)
{
var readGzipBuffer = new GzipBuffer(readBuffer);
if (readGzipBuffer.NoHeaders)
{
gzipBuffer = default;
}
else
{
gzipBuffer = readGzipBuffer;
if (!endOfStream && readGzipBuffer.IsStartsWithCompressedBlock && readGzipBuffer.Headers.Count == 1)
{
endOfStream = stream.IsReadToTheEnd;
}
}
}
return(readBuffer.Count, endOfStream, gzipBuffer);
}
public override int Read(byte[] buffer, int offset, int count)
{
CheckStreamPosition();
if (buffer == null)
{
throw new ArgumentNullException(nameof(buffer));
}
if (offset < 0)
{
throw new ArgumentOutOfRangeException(nameof(offset), "Need non negative number");
}
if (count < 0)
{
throw new ArgumentOutOfRangeException(nameof(count), "Need non negative number");
}
if (buffer.Length - offset < count)
{
throw new ArgumentException($"Buffer have smaller elements {buffer.Length - offset} from given offset {offset} than requested in count {count}", nameof(count));
}
if (count == 0)
{
throw new ArgumentException("Requested zero elements", nameof(count));
}
if (count < GzipHeader.Length)
{
throw new ArgumentException("Buffer element count can't be less than Gzip header length", nameof(count));
}
if (buffer.Length - offset == 0)
{
throw new ArgumentException("Buffer has no elements from requested offset", nameof(offset));
}
var currentGzipBuffer = leftBuffer;
var isEnd = streamEnded;
var read = 0;
if (currentGzipBuffer.IsEmpty && !streamEnded)
{
(read, isEnd, currentGzipBuffer) = ReadGzipBufferFromStream();
}
if (!currentGzipBuffer.IsEmpty)
{
ArraySegment <byte> readBlock;
(readBlock, currentGzipBuffer) = ReadFirstBockFromBuffer(currentGzipBuffer, count);
read = readBlock.Count;
if (readBlock.Array != null && readBlock.Count > 0)
{
Buffer.BlockCopy(readBlock.Array, readBlock.Offset, buffer, offset, readBlock.Count);
}
}
leftBuffer = currentGzipBuffer;
position += read;
streamEnded = isEnd;
return(read);
(int Read, bool StreamIsEnd, GzipBuffer gzipBuffer) ReadGzipBufferFromStream()
{
GzipBuffer gzipBuffer = default;
var(readBuffer, endOfStream) = stream.ReadExactBuffer(buffer, offset, count);
if (readBuffer.Count > 0)
{
var readGzipBuffer = new GzipBuffer(readBuffer);
gzipBuffer = readGzipBuffer.NoHeadersOrParts || readGzipBuffer.ContainsOnlyOneCompressedBlockFromStart
? default
: readGzipBuffer.ToOwnedBuffer();
}
return(readBuffer.Count, endOfStream, gzipBuffer);
}
(ArraySegment <byte> Block, GzipBuffer LeftGzipBuffer) ReadFirstBockFromBuffer(GzipBuffer gzipBuffer, int requestedCount)
{
var(block, left) = gzipBuffer.CutFirstBlock();
if (block.Array == null || block.Count == 0)
{
if (left.ContainsOnlyPart)
{
block = gzipBuffer.GetPossiblePart();
}
left = default;
}
else if (block.Count > requestedCount)
{
block = block.Slice(block.Offset, requestedCount);
var returnBlock = block.Slice(block.Offset + requestedCount, block.Count - requestedCount);
left = left.ReturnToStart(returnBlock);
}
return(block, left);
}
}
