void ReedSolomonDecoder::decode(ArrayRef<int> received, int twoS) {
Ref<GenericGFPoly> poly(new GenericGFPoly(field, received));
#ifdef DEBUG
cout << "decoding with poly " << *poly << "\n";
#endif
ArrayRef<int> syndromeCoefficients(new Array<int> (twoS));
#ifdef DEBUG
cout << "syndromeCoefficients array = " <<
syndromeCoefficients.array_ << "\n";
#endif
bool dataMatrix = (field.object_ == GenericGF::DATA_MATRIX_FIELD_256.object_);
bool noError = true;
for (int i = 0; i < twoS; i++) {
int eval = poly->evaluateAt(field->exp(dataMatrix ? i + 1 : i));
syndromeCoefficients[syndromeCoefficients->size() - 1 - i] = eval;
if (eval != 0) {
noError = false;
}
}
if (noError) {
return;
}
Ref<GenericGFPoly> syndrome(new GenericGFPoly(field, syndromeCoefficients));
Ref<GenericGFPoly> monomial = field->buildMonomial(twoS, 1);
vector<Ref<GenericGFPoly> > sigmaOmega = runEuclideanAlgorithm(monomial, syndrome, twoS);
ArrayRef<int> errorLocations = findErrorLocations(sigmaOmega[0]);
ArrayRef<int> errorMagitudes = findErrorMagnitudes(sigmaOmega[1], errorLocations, dataMatrix);
for (unsigned i = 0; i < errorLocations->size(); i++) {
int position = received->size() - 1 - field->log(errorLocations[i]);
//TODO: check why the position would be invalid
if (position < 0 || (size_t)position >= received.size())
throw IllegalArgumentException("Invalid position (ReedSolomonDecoder)");
received[position] = GenericGF::addOrSubtract(received[position], errorMagitudes[i]);
}
}
void ReedSolomonDecoder::decode(ArrayRef<int> received, int twoS) {
Ref<GF256Poly> poly(new GF256Poly(field, received));
#ifdef DEBUG
cout << "decoding with poly " << *poly << "\n";
#endif
ArrayRef<int> syndromeCoefficients(new Array<int>(twoS));
#ifdef DEBUG
cout << "syndromeCoefficients array = " <<
syndromeCoefficients.array_ << "\n";
#endif
bool noError = true;
for (int i = 0; i < twoS; i++) {
int eval = poly->evaluateAt(field.exp(i));
syndromeCoefficients[syndromeCoefficients->size() - 1 - i] = eval;
if (eval != 0) {
noError = false;
}
}
if (noError) {
return;
}
Ref<GF256Poly> syndrome(new GF256Poly(field, syndromeCoefficients));
Ref<GF256Poly> monomial(field.buildMonomial(twoS, 1));
vector<Ref<GF256Poly> > sigmaOmega
(runEuclideanAlgorithm(monomial, syndrome, twoS));
ArrayRef<int> errorLocations = findErrorLocations(sigmaOmega[0]);
ArrayRef<int> errorMagitudes = findErrorMagnitudes(sigmaOmega[1],
errorLocations);
for (unsigned i = 0; i < errorLocations->size(); i++) {
int position = received->size() - 1 - field.log(errorLocations[i]);
received[position] = GF256::addOrSubtract(received[position],
errorMagitudes[i]);
}
}
