Method decode

deps/zxing/core/src/zxing/pdf417/decoder/ec/ErrorCorrection.cpp:47–104

}

void ErrorCorrection::decode(ArrayRef<int> received,
                             int numECCodewords,
                             ArrayRef<int> erasures)
{
  Ref<ModulusPoly> poly (new ModulusPoly(field_, received));
  ArrayRef<int> S( new Array<int>(numECCodewords));
  bool error = false;
  for (int i = numECCodewords; i > 0; i--) {
    int eval = poly->evaluateAt(field_.exp(i));
    S[numECCodewords - i] = eval;
    if (eval != 0) {
      error = true;
    }
  }

  if (error) {

    Ref<ModulusPoly> knownErrors = field_.getOne();
    for (int i=0;i<erasures->size();i++) {
      int b = field_.exp(received->size() - 1 - erasures[i]);
      // Add (1 - bx) term:
      ArrayRef<int> one_minus_b_x(new Array<int>(2));
      one_minus_b_x[1]=field_.subtract(0,b);
      one_minus_b_x[0]=1;
      Ref<ModulusPoly> term (new ModulusPoly(field_,one_minus_b_x));
      knownErrors = knownErrors->multiply(term);
    }

    Ref<ModulusPoly> syndrome (new ModulusPoly(field_, S));
    //syndrome = syndrome.multiply(knownErrors);

    vector<Ref<ModulusPoly> > sigmaOmega (
        runEuclideanAlgorithm(field_.buildMonomial(numECCodewords, 1), syndrome, numECCodewords));
    Ref<ModulusPoly> sigma = sigmaOmega[0];
    Ref<ModulusPoly> omega = sigmaOmega[1];

    //sigma = sigma.multiply(knownErrors);

    ArrayRef<int> errorLocations = findErrorLocations(sigma);
    ArrayRef<int> errorMagnitudes = findErrorMagnitudes(omega, sigma, errorLocations);

    for (int i = 0; i < errorLocations->size(); i++) {
      int position = received->size() - 1 - field_.log(errorLocations[i]);
      if (position < 0) {
        throw ReedSolomonException("Bad error location!");
      }
      received[position] = field_.subtract(received[position], errorMagnitudes[i]);
#if (defined (DEBUG)  && defined _WIN32)
      {
        WCHAR szmsg[256];
        swprintf(szmsg,L"ErrorCorrection::decode: fix @ %d, new value = %d\n",
                 position, received[position]);
        OutputDebugString(szmsg);
      }
#endif
    }
  }
}