msb-public
/
QR-Code-generator
mirror of https://github.com/nayuki/QR-Code-generator
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Heavily rearranged functions in C code without making internal changes, also added/updated section heading comments.

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pull/11/head
Project Nayuki 9 years ago
parent 8cb33d44d8
commit aa50d1906d
1 changed files with 257 additions and 250 deletions
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507
c/qrcodegen.c
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@ -40,13 +40,15 @@
static int getTextProperties(const char *text, bool *isNumeric, bool *isAlphanumeric, int *textBits);
static int fitVersionToData(int minVersion, int maxVersion, enum qrcodegen_Ecc ecl, int dataLen, int dataBitLen, int ver1To9LenBits, int ver10To26LenBits, int ver27To40LenBits);
static void encodeQrCodeTail(uint8_t dataAndQrcode[], int bitLen, uint8_t tempBuffer[], int version, enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, bool boostEcl);
static long getPenaltyScore(const uint8_t qrcode[], int qrsize);
static void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[], int *bitLen);
static void appendErrorCorrection(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[]);
static int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl);
static int getNumRawDataModules(int version);
static bool getModule(const uint8_t qrcode[], int qrsize, int x, int y);
static void setModule(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack);
static void setModuleBounded(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack);
static void calcReedSolomonGenerator(int degree, uint8_t result[]);
static void calcReedSolomonRemainder(const uint8_t data[], int dataLen, const uint8_t generator[], int degree, uint8_t result[]);
static uint8_t finiteFieldMultiply(uint8_t x, uint8_t y);
static void initializeFunctionModules(int version, uint8_t qrcode[]);
static void drawWhiteFunctionModules(uint8_t qrcode[], int version);
@ -54,14 +56,13 @@ static void drawFormatBits(enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, uin
static int getAlignmentPatternPositions(int version, uint8_t result[7]);
static void fillRectangle(int left, int top, int width, int height, uint8_t qrcode[], int qrsize);
static void appendErrorCorrection(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[]);
static int getNumRawDataModules(int version);
static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[], int qrsize);
static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], int qrsize, int mask);
static long getPenaltyScore(const uint8_t qrcode[], int qrsize);
static void calcReedSolomonGenerator(int degree, uint8_t result[]);
static void calcReedSolomonRemainder(const uint8_t data[], int dataLen, const uint8_t generator[], int degree, uint8_t result[]);
static uint8_t finiteFieldMultiply(uint8_t x, uint8_t y);
static bool getModule(const uint8_t qrcode[], int qrsize, int x, int y);
static void setModule(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack);
static void setModuleBounded(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack);
@ -98,7 +99,7 @@ static const int PENALTY_N4 = 10;
/*---- Top-level QR Code encoding functions ----*/
/*---- High-level QR Code encoding functions ----*/
// Public function - see documentation comment in header file.
int qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[],
@ -170,6 +171,32 @@ int qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[
}
// Public function - see documentation comment in header file.
int qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcode[],
enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl) {
assert(qrcodegen_VERSION_MIN <= minVersion && minVersion <= maxVersion && maxVersion <= qrcodegen_VERSION_MAX);
assert(0 <= (int)ecl && (int)ecl <= 3 && -1 <= (int)mask && (int)mask <= 7);
// Check length and find version
if (dataLen > INT16_MAX / 8)
return 0;
// Now dataLen * 8 <= 32767 <= INT_MAX
int version = fitVersionToData(minVersion, maxVersion, ecl, (int)dataLen, (int)dataLen * 8, 8, 16, 16);
if (version == 0)
return 0;
// Make bit sequence and QR Code
memset(qrcode, 0, qrcodegen_BUFFER_LEN_FOR_VERSION(version) * sizeof(qrcode[0]));
int bitLen = 0;
appendBitsToBuffer(4, 4, qrcode, &bitLen);
appendBitsToBuffer((unsigned int)dataLen, (version <= 9 ? 8 : 16), qrcode, &bitLen);
for (size_t i = 0; i < dataLen; i++)
appendBitsToBuffer(dataAndTemp[i], 8, qrcode, &bitLen);
encodeQrCodeTail(qrcode, bitLen, dataAndTemp, version, ecl, mask, boostEcl);
return version;
}
// Scans the given string, returns the number of characters, and sets output variables.
// Returns a negative number if the length would exceed INT16_MAX or textBits would exceed INT_MAX.
// Note that INT16_MAX <= 32767 <= INT_MAX and INT16_MAX < 65535 <= SIZE_MAX.
@ -203,32 +230,6 @@ static int getTextProperties(const char *text, bool *isNumeric, bool *isAlphanum
}
// Public function - see documentation comment in header file.
int qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcode[],
enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl) {
assert(qrcodegen_VERSION_MIN <= minVersion && minVersion <= maxVersion && maxVersion <= qrcodegen_VERSION_MAX);
assert(0 <= (int)ecl && (int)ecl <= 3 && -1 <= (int)mask && (int)mask <= 7);
// Check length and find version
if (dataLen > INT16_MAX / 8)
return 0;
// Now dataLen * 8 <= 32767 <= INT_MAX
int version = fitVersionToData(minVersion, maxVersion, ecl, (int)dataLen, (int)dataLen * 8, 8, 16, 16);
if (version == 0)
return 0;
// Make bit sequence and QR Code
memset(qrcode, 0, qrcodegen_BUFFER_LEN_FOR_VERSION(version) * sizeof(qrcode[0]));
int bitLen = 0;
appendBitsToBuffer(4, 4, qrcode, &bitLen);
appendBitsToBuffer((unsigned int)dataLen, (version <= 9 ? 8 : 16), qrcode, &bitLen);
for (size_t i = 0; i < dataLen; i++)
appendBitsToBuffer(dataAndTemp[i], 8, qrcode, &bitLen);
encodeQrCodeTail(qrcode, bitLen, dataAndTemp, version, ecl, mask, boostEcl);
return version;
}
// Returns the minimum possible version in the given range to fit one
// segment with the given characteristics, or 0 if no version fits the data.
static int fitVersionToData(int minVersion, int maxVersion, enum qrcodegen_Ecc ecl,
@ -312,88 +313,6 @@ static void encodeQrCodeTail(uint8_t dataAndQrcode[], int bitLen, uint8_t tempBu
}
// Calculates and returns the penalty score based on state of the given QR Code's current modules.
// This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
static long getPenaltyScore(const uint8_t qrcode[], int qrsize) {
long result = 0;
// Adjacent modules in row having same color
for (int y = 0; y < qrsize; y++) {
bool colorX = getModule(qrcode, qrsize, 0, y);
for (int x = 1, runX = 1; x < qrsize; x++) {
if (getModule(qrcode, qrsize, x, y) != colorX) {
colorX = getModule(qrcode, qrsize, x, y);
runX = 1;
} else {
runX++;
if (runX == 5)
result += PENALTY_N1;
else if (runX > 5)
result++;
}
}
}
// Adjacent modules in column having same color
for (int x = 0; x < qrsize; x++) {
bool colorY = getModule(qrcode, qrsize, x, 0);
for (int y = 1, runY = 1; y < qrsize; y++) {
if (getModule(qrcode, qrsize, x, y) != colorY) {
colorY = getModule(qrcode, qrsize, x, y);
runY = 1;
} else {
runY++;
if (runY == 5)
result += PENALTY_N1;
else if (runY > 5)
result++;
}
}
}
// 2*2 blocks of modules having same color
for (int y = 0; y < qrsize - 1; y++) {
for (int x = 0; x < qrsize - 1; x++) {
bool color = getModule(qrcode, qrsize, x, y);
if ( color == getModule(qrcode, qrsize, x + 1, y) &&
color == getModule(qrcode, qrsize, x, y + 1) &&
color == getModule(qrcode, qrsize, x + 1, y + 1))
result += PENALTY_N2;
}
}
// Finder-like pattern in rows
for (int y = 0; y < qrsize; y++) {
for (int x = 0, bits = 0; x < qrsize; x++) {
bits = ((bits << 1) & 0x7FF) | (getModule(qrcode, qrsize, x, y) ? 1 : 0);
if (x >= 10 && (bits == 0x05D || bits == 0x5D0)) // Needs 11 bits accumulated
result += PENALTY_N3;
}
}
// Finder-like pattern in columns
for (int x = 0; x < qrsize; x++) {
for (int y = 0, bits = 0; y < qrsize; y++) {
bits = ((bits << 1) & 0x7FF) | (getModule(qrcode, qrsize, x, y) ? 1 : 0);
if (y >= 10 && (bits == 0x05D || bits == 0x5D0)) // Needs 11 bits accumulated
result += PENALTY_N3;
}
}
// Balance of black and white modules
int black = 0;
for (int y = 0; y < qrsize; y++) {
for (int x = 0; x < qrsize; x++) {
if (getModule(qrcode, qrsize, x, y))
black++;
}
}
int total = qrsize * qrsize;
// Find smallest k such that (45-5k)% <= dark/total <= (55+5k)%
for (int k = 0; black*20L < (9L-k)*total || black*20L > (11L+k)*total; k++)
result += PENALTY_N4;
return result;
}
// Appends the given sequence of bits to the given byte-based bit buffer, increasing the bit length.
static void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[], int *bitLen) {
assert(0 <= numBits && numBits <= 16 && (long)val >> numBits == 0);
@ -402,6 +321,52 @@ static void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[],
}
/*---- Error correction code generation functions ----*/
// Appends error correction bytes to each block of the given data array, then interleaves bytes
// from the blocks and stores them in the result array. data[0 : rawCodewords - totalEcc] contains
// the input data. data[rawCodewords - totalEcc : rawCodewords] is used as a temporary work area
// and will be clobbered by this function. The final answer is stored in result[0 : rawCodewords].
static void appendErrorCorrection(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[]) {
// Calculate parameter numbers
assert(0 <= (int)ecl && (int)ecl < 4 && qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[(int)ecl][version];
int blockEccLen = ECC_CODEWORDS_PER_BLOCK[(int)ecl][version];
int rawCodewords = getNumRawDataModules(version) / 8;
int dataLen = rawCodewords - blockEccLen * numBlocks;
int numShortBlocks = numBlocks - rawCodewords % numBlocks;
int shortBlockDataLen = rawCodewords / numBlocks - blockEccLen;
// Split data into blocks and append ECC after all data
uint8_t generator[30];
calcReedSolomonGenerator(blockEccLen, generator);
for (int i = 0, j = dataLen, k = 0; i < numBlocks; i++) {
int blockLen = shortBlockDataLen;
if (i >= numShortBlocks)
blockLen++;
calcReedSolomonRemainder(&data[k], blockLen, generator, blockEccLen, &data[j]);
j += blockEccLen;
k += blockLen;
}
// Interleave (not concatenate) the bytes from every block into a single sequence
for (int i = 0, k = 0; i < numBlocks; i++) {
for (int j = 0, l = i; j < shortBlockDataLen; j++, k++, l += numBlocks)
result[l] = data[k];
if (i >= numShortBlocks)
k++;
}
for (int i = numShortBlocks, k = (numShortBlocks + 1) * shortBlockDataLen, l = numBlocks * shortBlockDataLen;
i < numBlocks; i++, k += shortBlockDataLen + 1, l++)
result[l] = data[k];
for (int i = 0, k = dataLen; i < numBlocks; i++) {
for (int j = 0, l = dataLen + i; j < blockEccLen; j++, k++, l += numBlocks)
result[l] = data[k];
}
}
// Returns the number of 8-bit codewords that can be used for storing data (not ECC),
// for the given version number and error correction level. The result is in the range [9, 2956].
static int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl) {
@ -410,55 +375,78 @@ static int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl) {
}
/*---- Basic QR Code information functions ----*/
// Public function - see documentation comment in header file.
int qrcodegen_getSize(int version) {
// Returns the number of data bits that can be stored in a QR Code of the given version number, after
// all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8.
// The result is in the range [208, 29648].
static int getNumRawDataModules(int version) {
assert(qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
return version * 4 + 17;
int result = (16 * version + 128) * version + 64;
if (version >= 2) {
int numAlign = version / 7 + 2;
result -= (25 * numAlign - 10) * numAlign - 55;
if (version >= 7)
result -= 18 * 2; // Subtract version information
}
return result;
}
// Public function - see documentation comment in header file.
bool qrcodegen_getModule(const uint8_t qrcode[], int version, int x, int y) {
int qrsize = qrcodegen_getSize(version);
return (0 <= x && x < qrsize && 0 <= y && y < qrsize) && getModule(qrcode, qrsize, x, y);
}
/*---- Reed-Solomon ECC generator functions ----*/
// Gets the module at the given coordinates, which must be in bounds.
static bool getModule(const uint8_t qrcode[], int qrsize, int x, int y) {
assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
int index = y * qrsize + x;
int bitIndex = index & 7;
int byteIndex = index >> 3;
return ((qrcode[byteIndex] >> bitIndex) & 1) != 0;
// Calculates the Reed-Solomon generator polynomial of the given degree, storing in result[0 : degree].
static void calcReedSolomonGenerator(int degree, uint8_t result[]) {
// Start with the monomial x^0
assert(1 <= degree && degree <= 30);
memset(result, 0, degree * sizeof(result[0]));
result[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).
int root = 1;
for (int i = 0; i < degree; i++) {
// Multiply the current product by (x - r^i)
for (int j = 0; j < degree; j++) {
result[j] = finiteFieldMultiply(result[j], (uint8_t)root);
if (j + 1 < degree)
result[j] ^= result[j + 1];
}
root = (root << 1) ^ ((root >> 7) * 0x11D); // Multiply by 0x02 mod GF(2^8/0x11D)
}
}
// Sets the module at the given coordinates, which must be in bounds.
static void setModule(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack) {
assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
int index = y * qrsize + x;
int bitIndex = index & 7;
int byteIndex = index >> 3;
if (isBlack)
qrcode[byteIndex] |= 1 << bitIndex;
else
qrcode[byteIndex] &= (1 << bitIndex) ^ 0xFF;
// Calculates the remainder of the polynomial data[0 : dataLen] when divided by the generator[0 : degree], where all
// polynomials are in big endian and the generator has an implicit leading 1 term, storing the result in result[0 : degree].
static void calcReedSolomonRemainder(const uint8_t data[], int dataLen, const uint8_t generator[], int degree, uint8_t result[]) {
// Perform polynomial division
assert(1 <= degree && degree <= 30);
memset(result, 0, degree * sizeof(result[0]));
for (int i = 0; i < dataLen; i++) {
uint8_t factor = data[i] ^ result[0];
memmove(&result[0], &result[1], (degree - 1) * sizeof(result[0]));
result[degree - 1] = 0;
for (int j = 0; j < degree; j++)
result[j] ^= finiteFieldMultiply(generator[j], factor);
}
}
// Sets the module at the given coordinates, doing nothing if out of bounds.
static void setModuleBounded(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack) {
if (0 <= x && x < qrsize && 0 <= y && y < qrsize)
setModule(qrcode, qrsize, x, y, isBlack);
// Returns the product of the two given field elements modulo GF(2^8/0x11D). All argument values are valid.
static uint8_t finiteFieldMultiply(uint8_t x, uint8_t y) {
// Russian peasant multiplication
uint8_t z = 0;
for (int i = 7; i >= 0; i--) {
z = (z << 1) ^ ((z >> 7) * 0x11D);
z ^= ((y >> i) & 1) * x;
}
return z;
}
/*---- QR Code drawing functions ----*/
/*---- Drawing function modules ----*/
// Clears the given QR Code grid with white modules for the given
// version's size, then marks every function module as black.
@ -627,64 +615,8 @@ static void fillRectangle(int left, int top, int width, int height, uint8_t qrco
}
// Appends error correction bytes to each block of the given data array, then interleaves bytes
// from the blocks and stores them in the result array. data[0 : rawCodewords - totalEcc] contains
// the input data. data[rawCodewords - totalEcc : rawCodewords] is used as a temporary work area
// and will be clobbered by this function. The final answer is stored in result[0 : rawCodewords].
static void appendErrorCorrection(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[]) {
// Calculate parameter numbers
assert(0 <= (int)ecl && (int)ecl < 4 && qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[(int)ecl][version];
int blockEccLen = ECC_CODEWORDS_PER_BLOCK[(int)ecl][version];
int rawCodewords = getNumRawDataModules(version) / 8;
int dataLen = rawCodewords - blockEccLen * numBlocks;
int numShortBlocks = numBlocks - rawCodewords % numBlocks;
int shortBlockDataLen = rawCodewords / numBlocks - blockEccLen;
// Split data into blocks and append ECC after all data
uint8_t generator[30];
calcReedSolomonGenerator(blockEccLen, generator);
for (int i = 0, j = dataLen, k = 0; i < numBlocks; i++) {
int blockLen = shortBlockDataLen;
if (i >= numShortBlocks)
blockLen++;
calcReedSolomonRemainder(&data[k], blockLen, generator, blockEccLen, &data[j]);
j += blockEccLen;
k += blockLen;
}
// Interleave (not concatenate) the bytes from every block into a single sequence
for (int i = 0, k = 0; i < numBlocks; i++) {
for (int j = 0, l = i; j < shortBlockDataLen; j++, k++, l += numBlocks)
result[l] = data[k];
if (i >= numShortBlocks)
k++;
}
for (int i = numShortBlocks, k = (numShortBlocks + 1) * shortBlockDataLen, l = numBlocks * shortBlockDataLen;
i < numBlocks; i++, k += shortBlockDataLen + 1, l++)
result[l] = data[k];
for (int i = 0, k = dataLen; i < numBlocks; i++) {
for (int j = 0, l = dataLen + i; j < blockEccLen; j++, k++, l += numBlocks)
result[l] = data[k];
}
}
// Returns the number of data bits that can be stored in a QR Code of the given version number, after
// all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8.
// The result is in the range [208, 29648].
static int getNumRawDataModules(int version) {
assert(qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
int result = (16 * version + 128) * version + 64;
if (version >= 2) {
int numAlign = version / 7 + 2;
result -= (25 * numAlign - 10) * numAlign - 55;
if (version >= 7)
result -= 18 * 2; // Subtract version information
}
return result;
}
/*---- Drawing data modules and masking ----*/
// Draws the raw codewords (including data and ECC) onto the given QR Code. This requires the initial state of
// the QR Code to be black at function modules and white at codeword modules (including unused remainder bits).
@ -713,9 +645,6 @@ static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[], i
}
/*---- Reed-Solomon ECC generator functions ----*/
// XORs the data modules in this QR Code with the given mask pattern. Due to XOR's mathematical
// properties, calling applyMask(..., m) twice with the same value is equivalent to no change at all.
// This means it is possible to apply a mask, undo it, and try another mask. Note that a final
@ -745,52 +674,130 @@ static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], int qrs
}
// Calculates the Reed-Solomon generator polynomial of the given degree, storing in result[0 : degree].
static void calcReedSolomonGenerator(int degree, uint8_t result[]) {
// Start with the monomial x^0
assert(1 <= degree && degree <= 30);
memset(result, 0, degree * sizeof(result[0]));
result[degree - 1] = 1;
// Calculates and returns the penalty score based on state of the given QR Code's current modules.
// This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
static long getPenaltyScore(const uint8_t qrcode[], int qrsize) {
long result = 0;
// 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).
int root = 1;
for (int i = 0; i < degree; i++) {
// Multiply the current product by (x - r^i)
for (int j = 0; j < degree; j++) {
result[j] = finiteFieldMultiply(result[j], (uint8_t)root);
if (j + 1 < degree)
result[j] ^= result[j + 1];
// Adjacent modules in row having same color
for (int y = 0; y < qrsize; y++) {
bool colorX = getModule(qrcode, qrsize, 0, y);
for (int x = 1, runX = 1; x < qrsize; x++) {
if (getModule(qrcode, qrsize, x, y) != colorX) {
colorX = getModule(qrcode, qrsize, x, y);
runX = 1;
} else {
runX++;
if (runX == 5)
result += PENALTY_N1;
else if (runX > 5)
result++;
}
}
}
// Adjacent modules in column having same color
for (int x = 0; x < qrsize; x++) {
bool colorY = getModule(qrcode, qrsize, x, 0);
for (int y = 1, runY = 1; y < qrsize; y++) {
if (getModule(qrcode, qrsize, x, y) != colorY) {
colorY = getModule(qrcode, qrsize, x, y);
runY = 1;
} else {
runY++;
if (runY == 5)
result += PENALTY_N1;
else if (runY > 5)
result++;
}
}
}
// 2*2 blocks of modules having same color
for (int y = 0; y < qrsize - 1; y++) {
for (int x = 0; x < qrsize - 1; x++) {
bool color = getModule(qrcode, qrsize, x, y);
if ( color == getModule(qrcode, qrsize, x + 1, y) &&
color == getModule(qrcode, qrsize, x, y + 1) &&
color == getModule(qrcode, qrsize, x + 1, y + 1))
result += PENALTY_N2;
}
root = (root << 1) ^ ((root >> 7) * 0x11D); // Multiply by 0x02 mod GF(2^8/0x11D)
}
// Finder-like pattern in rows
for (int y = 0; y < qrsize; y++) {
for (int x = 0, bits = 0; x < qrsize; x++) {
bits = ((bits << 1) & 0x7FF) | (getModule(qrcode, qrsize, x, y) ? 1 : 0);
if (x >= 10 && (bits == 0x05D || bits == 0x5D0)) // Needs 11 bits accumulated
result += PENALTY_N3;
}
}
// Finder-like pattern in columns
for (int x = 0; x < qrsize; x++) {
for (int y = 0, bits = 0; y < qrsize; y++) {
bits = ((bits << 1) & 0x7FF) | (getModule(qrcode, qrsize, x, y) ? 1 : 0);
if (y >= 10 && (bits == 0x05D || bits == 0x5D0)) // Needs 11 bits accumulated
result += PENALTY_N3;
}
}
// Balance of black and white modules
int black = 0;
for (int y = 0; y < qrsize; y++) {
for (int x = 0; x < qrsize; x++) {
if (getModule(qrcode, qrsize, x, y))
black++;
}
}
int total = qrsize * qrsize;
// Find smallest k such that (45-5k)% <= dark/total <= (55+5k)%
for (int k = 0; black*20L < (9L-k)*total || black*20L > (11L+k)*total; k++)
result += PENALTY_N4;
return result;
}
// Calculates the remainder of the polynomial data[0 : dataLen] when divided by the generator[0 : degree], where all
// polynomials are in big endian and the generator has an implicit leading 1 term, storing the result in result[0 : degree].
static void calcReedSolomonRemainder(const uint8_t data[], int dataLen, const uint8_t generator[], int degree, uint8_t result[]) {
// Perform polynomial division
assert(1 <= degree && degree <= 30);
memset(result, 0, degree * sizeof(result[0]));
for (int i = 0; i < dataLen; i++) {
uint8_t factor = data[i] ^ result[0];
memmove(&result[0], &result[1], (degree - 1) * sizeof(result[0]));
result[degree - 1] = 0;
for (int j = 0; j < degree; j++)
result[j] ^= finiteFieldMultiply(generator[j], factor);
}
/*---- Basic QR Code information ----*/
// Public function - see documentation comment in header file.
int qrcodegen_getSize(int version) {
assert(qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
return version * 4 + 17;
}
// Returns the product of the two given field elements modulo GF(2^8/0x11D). All argument values are valid.
static uint8_t finiteFieldMultiply(uint8_t x, uint8_t y) {
// Russian peasant multiplication
uint8_t z = 0;
for (int i = 7; i >= 0; i--) {
z = (z << 1) ^ ((z >> 7) * 0x11D);
z ^= ((y >> i) & 1) * x;
}
return z;
// Public function - see documentation comment in header file.
bool qrcodegen_getModule(const uint8_t qrcode[], int version, int x, int y) {
int qrsize = qrcodegen_getSize(version);
return (0 <= x && x < qrsize && 0 <= y && y < qrsize) && getModule(qrcode, qrsize, x, y);
}
// Gets the module at the given coordinates, which must be in bounds.
static bool getModule(const uint8_t qrcode[], int qrsize, int x, int y) {
assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
int index = y * qrsize + x;
int bitIndex = index & 7;
int byteIndex = index >> 3;
return ((qrcode[byteIndex] >> bitIndex) & 1) != 0;
}
// Sets the module at the given coordinates, which must be in bounds.
static void setModule(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack) {
assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
int index = y * qrsize + x;
int bitIndex = index & 7;
int byteIndex = index >> 3;
if (isBlack)
qrcode[byteIndex] |= 1 << bitIndex;
else
qrcode[byteIndex] &= (1 << bitIndex) ^ 0xFF;
}
// Sets the module at the given coordinates, doing nothing if out of bounds.
static void setModuleBounded(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack) {
if (0 <= x && x < qrsize && 0 <= y && y < qrsize)
setModule(qrcode, qrsize, x, y, isBlack);
}

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