public void WriteSimple()
{
var bs = new BitWriteStream(4);
bs.Write(0b_____101, 3);
bs.Write(0b_1001110, 7);
bs.Write(0b____0010, 4);
uint value = BitConverter.ToUInt32(bs.GetBytes(), 0);
Assert.AreEqual <uint>(0b_0010_1001110_101, value);
}
public void WriteOneBit()
{
var bs = new BitWriteStream(4);
uint expected = 0b10010011_11001001;
for (ulong b = expected; b != 0; b >>= 1)
{
bs.Write(b, 1);
}
uint value = BitConverter.ToUInt32(bs.GetBytes(), 0);
Assert.AreEqual <uint>(expected, value);
}
public void Combine()
{
var bs1 = new BitWriteStream();
bs1.Write(0b101010, 6);
bs1.Write(0b101010, 6);
var bs2 = new BitWriteStream();
bs2.Write(0b010101, 6);
bs2.Write(0b010101, 6);
var cb = BitWriteStream.Combine(new[] { bs1, bs2 });
Assert.AreEqual <byte>(0xAA, cb[0]);
Assert.AreEqual <byte>(0x5A, cb[1]);
Assert.AreEqual <byte>(0x55, cb[2]);
}
public EncodeResult Encode(byte[] data)
{
var flagOut = new List <BitWriteStream>();
var resOut = new BitWriteStream();
// Actual data length
int dataLength = data.Length;
// Perform specified number of rounds
for (int ri = 0; ri < rounds; ri++)
{
flagOut.Add(new BitWriteStream());
// Placeholder for header
resOut.Write(0UL, 8);
// Generate key set number
int kset = key.GetNextKeyset();
unsafe
{
// Use raw pointers to skip array bounds check
fixed(byte *dptr = data)
{
// Perform MV2 substitutions
for (int i = 0; i < dataLength; i++)
{
// Scramble byte values before MV2 lookup
byte val = key.Encode(key.XorByte(dptr[i], i), kset);
var(res, flag) = TransformTable.Encode(val);
resOut.Write(res);
flagOut[ri].Write(flag);
}
}
}
// Num. free bits in last byte
long fbits = 8 - (resOut.Position & 7);
// Fill the header
resOut[0] = (byte)((fbits & 7) | (kset << 3));
// Forward the residual to next round
data = resOut.GetBytesInternal();
dataLength = resOut.BytesWritten;
resOut.Reset();
// KLUDGE: Pad the flag bitstream to full byte
flagOut[ri].FinishByte();
// Terminate early if residual is too small
if (dataLength <= MinResidual)
{
break;
}
}
// Concatenate flag buffers into final array
var flagFinal = BitWriteStream.Combine(flagOut.Reverse <BitWriteStream>());
// Trim the residual
var resFinal = new byte[dataLength];
Array.Copy(data, resFinal, dataLength);
return(new EncodeResult {
Residual = resFinal, Flag = flagFinal
});
}
