System.IO.Compression.DeflateStream.ReadAsyncCore C# (CSharp) Method

        private async Task<int> ReadAsyncCore(Task<int> readTask, byte[] array, int offset, int count, CancellationToken cancellationToken)
        {
            try
            {
                while (true)
                {
                    int bytesRead = await readTask.ConfigureAwait(false);
                    EnsureNotDisposed();

                    if (bytesRead <= 0)
                    {
                        // This indicates the base stream has received EOF
                        return 0;
                    }
                    else if (bytesRead > _buffer.Length)
                    {
                        // The stream is either malicious or poorly implemented and returned a number of
                        // bytes larger than the buffer supplied to it.
                        throw new InvalidDataException(SR.GenericInvalidData);
                    }

                    cancellationToken.ThrowIfCancellationRequested();

                    // Feed the data from base stream into decompression engine
                    _inflater.SetInput(_buffer, 0, bytesRead);
                    bytesRead = _inflater.Inflate(array, offset, count);

                    if (bytesRead == 0 && !_inflater.Finished())
                    {
                        // We could have read in head information and didn't get any data.
                        // Read from the base stream again.   
                        readTask = _stream.ReadAsync(_buffer, 0, _buffer.Length, cancellationToken);
                        if (readTask == null)
                        {
                            throw new InvalidOperationException(SR.NotSupported_UnreadableStream);
                        }
                    }
                    else
                    {
                        return bytesRead;
                    }
                }
            }
            finally
            {
                AsyncOperationCompleting();
            }
        }