public override System.Int32 Read(System.Byte[] buffer, System.Int32 offset, System.Int32 count)
{
// According to MS documentation, any implementation of the IO.Stream.Read function must:
// (a) throw an exception if offset & count reference an invalid part of the buffer,
// or if count < 0, or if buffer is null
// (b) return 0 only upon EOF, or if count = 0
// (c) if not EOF, then return at least 1 byte, up to <count> bytes
if (_streamMode == StreamMode.Undefined)
{
if (!this._stream.CanRead)
{
throw new ZlibException("The stream is not readable.");
}
// for the first read, set up some controls.
_streamMode = StreamMode.Reader;
// (The first reference to _z goes through the private accessor which
// may initialize it.)
z.AvailableBytesIn = 0;
if (_flavor == ZlibStreamFlavor.GZIP)
{
_gzipHeaderByteCount = _ReadAndValidateGzipHeader();
// workitem 8501: handle edge case (decompress empty stream)
if (_gzipHeaderByteCount == 0)
{
return(0);
}
}
}
if (_streamMode != StreamMode.Reader)
{
throw new ZlibException("Cannot Read after Writing.");
}
if (count == 0)
{
return(0);
}
if (buffer == null)
{
throw new ArgumentNullException("buffer");
}
if (count < 0)
{
throw new ArgumentOutOfRangeException("count");
}
if (offset < buffer.GetLowerBound(0))
{
throw new ArgumentOutOfRangeException("offset");
}
if ((offset + count) > buffer.GetLength(0))
{
throw new ArgumentOutOfRangeException("count");
}
int rc = 0;
// set up the output of the deflate/inflate codec:
_z.OutputBuffer = buffer;
_z.NextOut = offset;
_z.AvailableBytesOut = count;
// This is necessary in case _workingBuffer has been resized. (new byte[])
// (The first reference to _workingBuffer goes through the private accessor which
// may initialize it.)
_z.InputBuffer = workingBuffer;
do
{
// need data in _workingBuffer in order to deflate/inflate. Here, we check if we have any.
if ((_z.AvailableBytesIn == 0) && (!nomoreinput))
{
// No data available, so try to Read data from the captive stream.
_z.NextIn = 0;
_z.AvailableBytesIn = _stream.Read(_workingBuffer, 0, _workingBuffer.Length);
if (_z.AvailableBytesIn == 0)
{
nomoreinput = true;
}
}
// we have data in InputBuffer; now compress or decompress as appropriate
rc = _z.Inflate(_flushMode);
if (nomoreinput && (rc == ZlibConstants.Z_BUF_ERROR))
{
return(0);
}
if (rc != ZlibConstants.Z_OK && rc != ZlibConstants.Z_STREAM_END)
{
throw new ZlibException(String.Format(CultureInfo.InvariantCulture, "inflating: rc={0} msg={1}", rc, _z.Message));
}
if ((nomoreinput || rc == ZlibConstants.Z_STREAM_END) && (_z.AvailableBytesOut == count))
{
break; // nothing more to read
}
}
//while (_z.AvailableBytesOut == count && rc == ZlibConstants.Z_OK);
while (_z.AvailableBytesOut > 0 && !nomoreinput && rc == ZlibConstants.Z_OK);
// workitem 8557
// is there more room in output?
if (_z.AvailableBytesOut > 0)
{
if (rc == ZlibConstants.Z_OK && _z.AvailableBytesIn == 0)
{
// deferred
}
}
rc = (count - _z.AvailableBytesOut);
// calculate CRC after reading
if (crc != null)
{
crc.SlurpBlock(buffer, offset, rc);
}
return(rc);
}
