/// <summary>ctor</summary>
public AesCtrCryptoTransform(byte[] key, ArraySegment<byte> counterBufferSegment, Func<Aes> aesFactory = null)
{
if (counterBufferSegment.Count != AesConstants.AES_BLOCK_SIZE)
throw new ArgumentException("counterBufferSegment.Count must be " + AesConstants.STR_AES_BLOCK_SIZE + ".");
var aes = aesFactory == null ? AesFactories.Aes() : aesFactory();
aes.Mode = CipherMode.ECB;
aes.Padding = PaddingMode.None;
var counterBufferSegmentArray = counterBufferSegment.Array;
var counterBufferSegmentOffset = counterBufferSegment.Offset;
byte[] counterBuffer_KeyStreamBuffer = this.counterBuffer_KeyStreamBuffer; // looks dumb, but local-access is faster than field-access
System.Diagnostics.Debug.Assert(AesConstants.AES_BLOCK_SIZE == 16);
//Utils.BlockCopy(counterBufferSegment.Array, counterBufferSegment.Offset, counterBuffer_KeyStreamBuffer, 0, AesConstants.AES_BLOCK_SIZE);
counterBuffer_KeyStreamBuffer[00] = counterBufferSegmentArray[counterBufferSegmentOffset + 00];
counterBuffer_KeyStreamBuffer[01] = counterBufferSegmentArray[counterBufferSegmentOffset + 01];
counterBuffer_KeyStreamBuffer[02] = counterBufferSegmentArray[counterBufferSegmentOffset + 02];
counterBuffer_KeyStreamBuffer[03] = counterBufferSegmentArray[counterBufferSegmentOffset + 03];
counterBuffer_KeyStreamBuffer[04] = counterBufferSegmentArray[counterBufferSegmentOffset + 04];
counterBuffer_KeyStreamBuffer[05] = counterBufferSegmentArray[counterBufferSegmentOffset + 05];
counterBuffer_KeyStreamBuffer[06] = counterBufferSegmentArray[counterBufferSegmentOffset + 06];
counterBuffer_KeyStreamBuffer[07] = counterBufferSegmentArray[counterBufferSegmentOffset + 07];
this.counterStruct = new Utils.LongStruct
{
B8 = counterBufferSegmentArray[counterBufferSegmentOffset + 08],
B7 = counterBufferSegmentArray[counterBufferSegmentOffset + 09],
B6 = counterBufferSegmentArray[counterBufferSegmentOffset + 10],
B5 = counterBufferSegmentArray[counterBufferSegmentOffset + 11],
B4 = counterBufferSegmentArray[counterBufferSegmentOffset + 12],
B3 = counterBufferSegmentArray[counterBufferSegmentOffset + 13],
B2 = counterBufferSegmentArray[counterBufferSegmentOffset + 14],
B1 = counterBufferSegmentArray[counterBufferSegmentOffset + 15]
};
this.cryptoTransform = aes.CreateEncryptor(rgbKey: key, rgbIV: null);
this.aes = aes;
}// ctor
}// ctor
#region public
public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
{
if (inputCount == 0) return 0;
int i, j, remainingInputCount = inputCount;
byte[] counterBuffer_KeyStreamBuffer = this.counterBuffer_KeyStreamBuffer; // looks dumb, but local-access is faster than field-access
// process any available key stream first
if (this.keyStreamBytesRemaining > 0)
{
j = inputCount > this.keyStreamBytesRemaining ? this.keyStreamBytesRemaining : inputCount;
for (i = 0; i < j; ++i)
outputBuffer[outputOffset + i] = (byte)(counterBuffer_KeyStreamBuffer[AesConstants.AES_BLOCK_SIZE * 2 - this.keyStreamBytesRemaining + i] ^ inputBuffer[inputOffset + i]);
this.keyStreamBytesRemaining -= j;
remainingInputCount -= j;
if (remainingInputCount == 0) return inputCount;
inputOffset += j;
outputOffset += j;
}
int fullBlockSize = (remainingInputCount >> 4) << 4;
int partialBlockSize = remainingInputCount - fullBlockSize;
var _counterStruct = this.counterStruct;
// process full blocks, if any
if (fullBlockSize > 0)
{
byte counterBuffer_00 = counterBuffer_KeyStreamBuffer[00];
byte counterBuffer_01 = counterBuffer_KeyStreamBuffer[01];
byte counterBuffer_02 = counterBuffer_KeyStreamBuffer[02];
byte counterBuffer_03 = counterBuffer_KeyStreamBuffer[03];
byte counterBuffer_04 = counterBuffer_KeyStreamBuffer[04];
byte counterBuffer_05 = counterBuffer_KeyStreamBuffer[05];
byte counterBuffer_06 = counterBuffer_KeyStreamBuffer[06];
byte counterBuffer_07 = counterBuffer_KeyStreamBuffer[07];
unchecked
{
for (i = outputOffset, /* reusing j as iMax */ j = outputOffset + fullBlockSize; i < j; i += AesConstants.AES_BLOCK_SIZE)
{
outputBuffer[i + 00] = counterBuffer_00;
outputBuffer[i + 01] = counterBuffer_01;
outputBuffer[i + 02] = counterBuffer_02;
outputBuffer[i + 03] = counterBuffer_03;
outputBuffer[i + 04] = counterBuffer_04;
outputBuffer[i + 05] = counterBuffer_05;
outputBuffer[i + 06] = counterBuffer_06;
outputBuffer[i + 07] = counterBuffer_07;
outputBuffer[i + 08] = _counterStruct.B8;
outputBuffer[i + 09] = _counterStruct.B7;
outputBuffer[i + 10] = _counterStruct.B6;
outputBuffer[i + 11] = _counterStruct.B5;
outputBuffer[i + 12] = _counterStruct.B4;
outputBuffer[i + 13] = _counterStruct.B3;
outputBuffer[i + 14] = _counterStruct.B2;
outputBuffer[i + 15] = _counterStruct.B1;
{ ++_counterStruct.UlongValue; };
}//for
}
fullBlockSize = this.cryptoTransform.TransformBlock(outputBuffer, outputOffset, fullBlockSize, outputBuffer, outputOffset);
i = 0;
const bool VECTORIZE = true;
if (VECTORIZE)
{ // vectorized xor
int vectorLength = Vector<byte>.Count, vectorLimit = (fullBlockSize / vectorLength) * vectorLength;
for (; i < vectorLimit; i += vectorLength)
{
var destVector = new Vector<byte>(outputBuffer, outputOffset + i);
var leftVector = new Vector<byte>(inputBuffer, inputOffset + i);
(destVector ^ leftVector).CopyTo(outputBuffer, outputOffset + i);
}
}
for (; i < fullBlockSize; ++i) outputBuffer[outputOffset + i] ^= inputBuffer[inputOffset + i];
}// if fullBlockSize > 0
// process the remaining partial block, if any
if (partialBlockSize > 0)
{
inputOffset += fullBlockSize;
outputOffset += fullBlockSize;
counterBuffer_KeyStreamBuffer[08] = _counterStruct.B8;
counterBuffer_KeyStreamBuffer[09] = _counterStruct.B7;
counterBuffer_KeyStreamBuffer[10] = _counterStruct.B6;
counterBuffer_KeyStreamBuffer[11] = _counterStruct.B5;
counterBuffer_KeyStreamBuffer[12] = _counterStruct.B4;
counterBuffer_KeyStreamBuffer[13] = _counterStruct.B3;
counterBuffer_KeyStreamBuffer[14] = _counterStruct.B2;
counterBuffer_KeyStreamBuffer[15] = _counterStruct.B1;
{ ++_counterStruct.UlongValue; };
this.cryptoTransform.TransformBlock(counterBuffer_KeyStreamBuffer, 0, AesConstants.AES_BLOCK_SIZE, counterBuffer_KeyStreamBuffer, AesConstants.AES_BLOCK_SIZE);
for (i = 0; i < partialBlockSize; ++i) outputBuffer[outputOffset + i] = (byte)(counterBuffer_KeyStreamBuffer[AesConstants.AES_BLOCK_SIZE + i] ^ inputBuffer[inputOffset + i]);
this.keyStreamBytesRemaining = AesConstants.AES_BLOCK_SIZE - partialBlockSize;
}//if partialBlockSize > 0
this.counterStruct = _counterStruct;
return inputCount;
}// TransformBlock()
