Demoted ReedSolomonGenerator from a class to a set of functions, and changed some names and comments, in all languages except C. This reduces code verbosity but doesn't change public APIs or visible behavior. The code organization is similar to the finder-like-pattern-detector feature.

cpp/QrCode.cpp

@@ -345,11 +345,11 @@ vector<uint8_t> QrCode::addEccAndInterleave(const vector<uint8_t> &data) const {
 	
 	// Split data into blocks and append ECC to each block
 	vector<vector<uint8_t> > blocks;
-	const ReedSolomonGenerator rs(blockEccLen);
+	const vector<uint8_t> rsDiv = reedSolomonComputeDivisor(blockEccLen);
 	for (int i = 0, k = 0; i < numBlocks; i++) {
 		vector<uint8_t> dat(data.cbegin() + k, data.cbegin() + (k + shortBlockLen - blockEccLen + (i < numShortBlocks ? 0 : 1)));
 		k += dat.size();
-		const vector<uint8_t> ecc = rs.getRemainder(dat);
+		const vector<uint8_t> ecc = reedSolomonComputeRemainder(dat, rsDiv);
 		if (i < numShortBlocks)
 			dat.push_back(0);
 		dat.insert(dat.end(), ecc.cbegin(), ecc.cend());
@@ -538,6 +538,57 @@ int QrCode::getNumDataCodewords(int ver, Ecc ecl) {
 }
 
 
+vector<uint8_t> QrCode::reedSolomonComputeDivisor(int degree) {
+	if (degree < 1 || degree > 255)
+		throw std::domain_error("Degree out of range");
+	// Polynomial coefficients are stored from highest to lowest power, excluding the leading term which is always 1.
+	// For example the polynomial x^3 + 255x^2 + 8x + 93 is stored as the uint8 array {255, 8, 93}.
+	vector<uint8_t> result(degree);
+	result.at(degree - 1) = 1;  // Start off with the monomial x^0
+	
+	// Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}),
+	// and drop the highest monomial term which is always 1x^degree.
+	// Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D).
+	uint8_t root = 1;
+	for (int i = 0; i < degree; i++) {
+		// Multiply the current product by (x - r^i)
+		for (size_t j = 0; j < result.size(); j++) {
+			result.at(j) = reedSolomonMultiply(result.at(j), root);
+			if (j + 1 < result.size())
+				result.at(j) ^= result.at(j + 1);
+		}
+		root = reedSolomonMultiply(root, 0x02);
+	}
+	return result;
+}
+
+
+vector<uint8_t> QrCode::reedSolomonComputeRemainder(const vector<uint8_t> &data, const vector<uint8_t> &divisor) {
+	vector<uint8_t> result(divisor.size());
+	for (uint8_t b : data) {  // Polynomial division
+		uint8_t factor = b ^ result.at(0);
+		result.erase(result.begin());
+		result.push_back(0);
+		for (size_t j = 0; j < result.size(); j++)
+			result.at(j) ^= reedSolomonMultiply(divisor.at(j), factor);
+	}
+	return result;
+}
+
+
+uint8_t QrCode::reedSolomonMultiply(uint8_t x, uint8_t y) {
+	// Russian peasant multiplication
+	int z = 0;
+	for (int i = 7; i >= 0; i--) {
+		z = (z << 1) ^ ((z >> 7) * 0x11D);
+		z ^= ((y >> i) & 1) * x;
+	}
+	if (z >> 8 != 0)
+		throw std::logic_error("Assertion error");
+	return static_cast<uint8_t>(z);
+}
+
+
 int QrCode::finderPenaltyCountPatterns(const std::array<int,7> &runHistory) const {
 	int n = runHistory.at(1);
 	if (n > size * 3)
@@ -597,58 +648,6 @@ const int8_t QrCode::NUM_ERROR_CORRECTION_BLOCKS[4][41] = {
 };
 
 
-QrCode::ReedSolomonGenerator::ReedSolomonGenerator(int degree) :
-		coefficients() {
-	if (degree < 1 || degree > 255)
-		throw std::domain_error("Degree out of range");
-	
-	// Start with the monomial x^0
-	coefficients.resize(degree);
-	coefficients.at(degree - 1) = 1;
-	
-	// Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}),
-	// drop the highest term, and store the rest of the coefficients in order of descending powers.
-	// Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D).
-	uint8_t root = 1;
-	for (int i = 0; i < degree; i++) {
-		// Multiply the current product by (x - r^i)
-		for (size_t j = 0; j < coefficients.size(); j++) {
-			coefficients.at(j) = multiply(coefficients.at(j), root);
-			if (j + 1 < coefficients.size())
-				coefficients.at(j) ^= coefficients.at(j + 1);
-		}
-		root = multiply(root, 0x02);
-	}
-}
-
-
-vector<uint8_t> QrCode::ReedSolomonGenerator::getRemainder(const vector<uint8_t> &data) const {
-	// Compute the remainder by performing polynomial division
-	vector<uint8_t> result(coefficients.size());
-	for (uint8_t b : data) {
-		uint8_t factor = b ^ result.at(0);
-		result.erase(result.begin());
-		result.push_back(0);
-		for (size_t j = 0; j < result.size(); j++)
-			result.at(j) ^= multiply(coefficients.at(j), factor);
-	}
-	return result;
-}
-
-
-uint8_t QrCode::ReedSolomonGenerator::multiply(uint8_t x, uint8_t y) {
-	// Russian peasant multiplication
-	int z = 0;
-	for (int i = 7; i >= 0; i--) {
-		z = (z << 1) ^ ((z >> 7) * 0x11D);
-		z ^= ((y >> i) & 1) * x;
-	}
-	if (z >> 8 != 0)
-		throw std::logic_error("Assertion error");
-	return static_cast<uint8_t>(z);
-}
-
-
 data_too_long::data_too_long(const std::string &msg) :
 	std::length_error(msg) {}