55 lines
1.6 KiB
C++
55 lines
1.6 KiB
C++
/*
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* Copyright 2016 Huy Cuong Nguyen
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* Copyright 2016 ZXing authors
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*/
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// SPDX-License-Identifier: Apache-2.0
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#include "ReedSolomonEncoder.h"
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#include "GenericGF.h"
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#include <algorithm>
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#include <iterator>
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#include <stdexcept>
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namespace ZXing {
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ReedSolomonEncoder::ReedSolomonEncoder(const GenericGF& field)
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: _field(&field)
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{
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_cachedGenerators.push_back(GenericGFPoly(field, { 1 }));
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}
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const GenericGFPoly&
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ReedSolomonEncoder::buildGenerator(int degree)
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{
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int cachedGenSize = Size(_cachedGenerators);
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if (degree >= cachedGenSize) {
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GenericGFPoly lastGenerator = _cachedGenerators.back();
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for (int d = cachedGenSize; d <= degree; d++) {
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lastGenerator.multiply(GenericGFPoly(*_field, { 1, _field->exp(d - 1 + _field->generatorBase()) }));
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_cachedGenerators.push_back(lastGenerator);
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}
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}
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return *std::next(_cachedGenerators.begin(), degree);
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}
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void
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ReedSolomonEncoder::encode(std::vector<int>& message, const int numECCodeWords)
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{
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if (numECCodeWords == 0 || numECCodeWords >= Size(message))
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throw std::invalid_argument("Invalid number of error correction code words");
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GenericGFPoly info = GenericGFPoly(*_field, std::vector<int>(message.begin(), message.end() - numECCodeWords));
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info.multiplyByMonomial(1, numECCodeWords);
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GenericGFPoly _;
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info.divide(buildGenerator(numECCodeWords), _);
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auto& coefficients = info.coefficients();
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int numZeroCoefficients = numECCodeWords - Size(coefficients);
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std::fill_n(message.end() - numECCodeWords, numZeroCoefficients, 0);
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std::copy(coefficients.begin(), coefficients.end(), message.end() - numECCodeWords + numZeroCoefficients);
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}
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} // ZXing
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