// This code is Reed Mahler's decoder for RM (30,14)
// The code is not universal, optimized for tetra
// Recovers 3 bits out of 30 transmitted.
public unsafe void Test()
{
var rnd = new Random();
var inTestBuffer = UnsafeBuffer.Create(32, sizeof(byte));
var inTestBufferPtr = (byte *)inTestBuffer;
var outTestBuffer = UnsafeBuffer.Create(14, sizeof(byte));
var outTestBufferPtr = (byte *)outTestBuffer;
var result = (uint)0;
var checkBit = (uint)0;
var error = 0;
// All possible options, 16K x 30 bits
for (int j = 1; j < 16384; j++)
{
result = 0;
for (int column = 0; column < 30; column++)
{
checkBit = 0;
for (int row = 0; row < 14; row++)
{
checkBit ^= (uint)((j >> (13 - row)) & 1) & gMatrix[row, column];
}
result <<= 1;
result |= (uint)checkBit;
}
var data = result;
for (int n = 0; n < 3; n++)
{
var bitNum = rnd.Next(0, 29);
data ^= (1u << bitNum);
}
TetraUtils.UIntToBits(data, inTestBufferPtr, 2);
Process(inTestBufferPtr, outTestBufferPtr);
data = TetraUtils.BitsToUInt32(outTestBufferPtr, 0, 14);
if ((result >> 16) != data)
{
error++;
}
}
}
public unsafe bool Process(byte *inBuffer, byte *outBuffer)
{
uint alphaValue = 0;
int counter = 0;
//Принятое кодовое слово
var vector = TetraUtils.BitsToUInt32(inBuffer, 0, n);
int syndromeI = 0;
for (int i = 0; i < nk; i++)
{
alphaValue = vector & _hMatrixUintPtr[i];
counter = _onesCounterPtr[alphaValue & 0xff]
+ _onesCounterPtr[(alphaValue >> 8) & 0xff]
+ _onesCounterPtr[(alphaValue >> 16) & 0xff]
+ _onesCounterPtr[(alphaValue >> 24) & 0xff];
syndromeI <<= 1;
syndromeI |= (counter & 1);
}
var noErrors = (syndromeI == 0);
if (!noErrors)
{
var bitMask = _syndromesDecoderPtr[syndromeI];
vector ^= bitMask;
noErrors = bitMask != 0;
}
for (int i = 0; i < k; i++)
{
outBuffer[i] = (byte)((vector & msb) == 0 ? 0 : 1);
vector <<= 1;
}
return(noErrors);
}
