Method appendErrorCorrection

Libraries/QRCode/tests/QrCode.cpp:301–340

std::vector<uint8_t> qrcodegen::QrCode::appendErrorCorrection(const std::vector<uint8_t> &data) const {
	if (data.size() != static_cast<unsigned int>(getNumDataCodewords(version, errorCorrectionLevel)))
		throw "Invalid argument";
	
	// Calculate parameter numbers
	int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[errorCorrectionLevel.ordinal][version];
	int totalEcc = NUM_ERROR_CORRECTION_CODEWORDS[errorCorrectionLevel.ordinal][version];
	if (totalEcc % numBlocks != 0)
		throw "Assertion error";
	int blockEccLen = totalEcc / numBlocks;
	int numShortBlocks = numBlocks - getNumRawDataModules(version) / 8 % numBlocks;
	int shortBlockLen = getNumRawDataModules(version) / 8 / numBlocks;
	
	// Split data into blocks and append ECC to each block
	std::vector<std::vector<uint8_t> > blocks;
	const ReedSolomonGenerator rs(blockEccLen);
	for (int i = 0, k = 0; i < numBlocks; i++) {
		std::vector<uint8_t> dat;
		dat.insert(dat.begin(), data.begin() + k, data.begin() + (k + shortBlockLen - blockEccLen + (i < numShortBlocks ? 0 : 1)));
		k += dat.size();
		const std::vector<uint8_t> ecc(rs.getRemainder(dat));
		if (i < numShortBlocks)
			dat.push_back(0);
		dat.insert(dat.end(), ecc.begin(), ecc.end());
		blocks.push_back(dat);
	}
	
	// Interleave (not concatenate) the bytes from every block into a single sequence
	std::vector<uint8_t> result;
	for (int i = 0; static_cast<unsigned int>(i) < blocks.at(0).size(); i++) {
		for (int j = 0; static_cast<unsigned int>(j) < blocks.size(); j++) {
			// Skip the padding byte in short blocks
			if (i != shortBlockLen - blockEccLen || j >= numShortBlocks)
				result.push_back(blocks.at(j).at(i));
		}
	}
	if (result.size() != static_cast<unsigned int>(getNumRawDataModules(version) / 8))
		throw "Assertion error";
	return result;
}


void qrcodegen::QrCode::drawCodewords(const std::vector<uint8_t> &data) {