public int InverseTransform(Buffer buffer, int length)
{
Log.Trace("BlockCipher.InverseTransform: input length {0}", length);
using (var decryptor = decryptionAlgorithm.CreateDecryptor(decryptionKey, decryptionIV))
using (var ms = new MemoryStream(length))
using (var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Write))
{
#if UNITY_WORKAROUND
// Workaround for ancient mono 2.0 of Unity3D
// Multiple Write() calls are not properly handled there.
byte[] ciphertext = buffer.ToArray();
if (Log.Level <= LogLevel.Trace)
{
Log.Trace("BlockCipher.InverseTransform: input {0}",
BitConverter.ToString(ciphertext, 0, length));
}
System.Buffer.BlockCopy(ciphertext, length - BlockSizeInBytes,
decryptionIV, 0, BlockSizeInBytes);
cs.Write(ciphertext, 0, length);
#else
var buffers = new List<ArraySegment<byte>>();
buffer.ListStartingSegments(buffers, length);
// Store the last ciphertext block as a next decryption IV.
byte[] nextIV = new byte[BlockSizeInBytes];
int bytesCopied = 0;
for (var i = buffers.Count - 1; bytesCopied < BlockSizeInBytes && i >= 0; --i)
{
var segment = buffers[i];
int bytesToCopy = Math.Min(segment.Count, BlockSizeInBytes);
System.Buffer.BlockCopy(segment.Array, segment.Offset + segment.Count - bytesToCopy,
decryptionIV, BlockSizeInBytes - bytesCopied - bytesToCopy, bytesToCopy);
bytesCopied += bytesToCopy;
}
for (var i = 0; i < buffers.Count; ++i)
{
var segment = buffers[i];
if (Log.Level <= LogLevel.Trace)
{
Log.Trace("BlockCipher.InverseTransform: input block {0}",
BitConverter.ToString(segment.Array, segment.Offset, segment.Count));
}
cs.Write(segment.Array, segment.Offset, segment.Count);
}
#endif
cs.FlushFinalBlock();
int result = (int)ms.Length;
var streamBuffer = ms.GetBuffer();
if (Log.Level <= LogLevel.Trace)
{
Log.Trace("BlockCipher.InverseTransform: output {0} {1}",
result, BitConverter.ToString(streamBuffer, 0, result));
}
buffer.Rewind();
buffer.CopyFrom(streamBuffer, 0, result);
return result;
}
}
