Crisis.Ionic.Zlib.ZlibBaseStream.Read C# (CSharp) Method

        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 (nomoreinput && _wantCompress) return 0;  // workitem 8557
            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 = (_wantCompress)
                    ? _z.Deflate(_flushMode)
                    : _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("{0}flating:  rc={1}  msg={2}", (_wantCompress ? "de" : "in"), 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
                }

                // are we completely done reading?
                if (nomoreinput)
                {
                    // and in compression?
                    if (_wantCompress)
                    {
                        // no more input data available; therefore we flush to
                        // try to complete the read
                        rc = _z.Deflate(FlushType.Finish);

                        if (rc != ZlibConstants.Z_OK && rc != ZlibConstants.Z_STREAM_END)
                            throw new ZlibException(String.Format("Deflating:  rc={0}  msg={1}", rc, _z.Message));
                    }
                }
            }


            rc = (count - _z.AvailableBytesOut);

            // calculate CRC after reading
            if (crc != null)
                crc.SlurpBlock(buffer, offset, rc);

            return rc;
        }

 /// <summary>
 /// Read data from the stream.
 /// </summary>
 /// <remarks>
 ///
 /// <para>
 ///   If you wish to use the <c>DeflateStream</c> to compress data while
 ///   reading, you can create a <c>DeflateStream</c> with
 ///   <c>CompressionMode.Compress</c>, providing an uncompressed data stream.
 ///   Then call Read() on that <c>DeflateStream</c>, and the data read will be
 ///   compressed as you read.  If you wish to use the <c>DeflateStream</c> to
 ///   decompress data while reading, you can create a <c>DeflateStream</c> with
 ///   <c>CompressionMode.Decompress</c>, providing a readable compressed data
 ///   stream.  Then call Read() on that <c>DeflateStream</c>, and the data read
 ///   will be decompressed as you read.
 /// </para>
 ///
 /// <para>
 ///   A <c>DeflateStream</c> can be used for <c>Read()</c> or <c>Write()</c>, but not both.
 /// </para>
 ///
 /// </remarks>
 /// <param name="buffer">The buffer into which the read data should be placed.</param>
 /// <param name="offset">the offset within that data array to put the first byte read.</param>
 /// <param name="count">the number of bytes to read.</param>
 /// <returns>the number of bytes actually read</returns>
 public override int Read(byte[] buffer, int offset, int count)
 {
     if (_disposed)
     {
         throw new ObjectDisposedException("DeflateStream");
     }
     return(_baseStream.Read(buffer, offset, count));
 }