internal void InitializeDeflater(Stream stream, bool leaveOpen, CompressionLevel compressionLevel)
{
Debug.Assert(stream != null);
if (!stream.CanWrite)
throw new ArgumentException(SR.NotSupported_UnwritableStream, nameof(stream));
_deflater = new DeflaterManaged();
_stream = stream;
_mode = CompressionMode.Compress;
_leaveOpen = leaveOpen;
_buffer = new byte[DefaultBufferSize];
}