private static async Task <MemoryStream> InternalGetDecryptionStreamAsync(Stream input, IMS2SizeHeader size, IBufferedCipher cipher, bool zlibCompressed) { using var cs = new CipherStream(input, cipher, null); byte[] bytes = new byte[size.Size]; int readBytes; if (zlibCompressed) { using var z = new ZlibStream(cs, CompressionMode.Decompress, true); readBytes = await z.ReadAsync(bytes, 0, bytes.Length).ConfigureAwait(false); } else { readBytes = await cs.ReadAsync(bytes, 0, bytes.Length).ConfigureAwait(false); } if (readBytes != size.Size) { throw new ArgumentException("Size bytes from input do not match with header size.", nameof(input)); } return(new MemoryStream(bytes)); }