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#include <assert.h>#include <limits.h>#include <stdlib.h>#include <string.h>#include "qrcodegen.h"
#ifndef QRCODEGEN_TEST #define testable static // Keep functions private#else #define testable // Expose private functions#endif
/*---- Forward declarations for private functions ----*/
// Regarding all public and private functions defined in this source file:// - They require all pointer/array arguments to be not null unless the array length is zero.// - They only read input scalar/array arguments, write to output pointer/array// arguments, and return scalar values; they are "pure" functions.// - They don't read mutable global variables or write to any global variables.// - They don't perform I/O, read the clock, print to console, etc.// - They allocate a small and constant amount of stack memory.// - They don't allocate or free any memory on the heap.// - They don't recurse or mutually recurse. All the code// could be inlined into the top-level public functions.// - They run in at most quadratic time with respect to input arguments.// Most functions run in linear time, and some in constant time.// There are no unbounded loops or non-obvious termination conditions.// - They are completely thread-safe if the caller does not give the// same writable buffer to concurrent calls to these functions.
testable void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[], int *bitLen);
testable void addEccAndInterleave(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[]);testable int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl);testable int getNumRawDataModules(int ver);
testable void reedSolomonComputeDivisor(int degree, uint8_t result[]);testable void reedSolomonComputeRemainder(const uint8_t data[], int dataLen, const uint8_t generator[], int degree, uint8_t result[]);testable uint8_t reedSolomonMultiply(uint8_t x, uint8_t y);
testable void initializeFunctionModules(int version, uint8_t qrcode[]);static void drawLightFunctionModules(uint8_t qrcode[], int version);static void drawFormatBits(enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, uint8_t qrcode[]);testable int getAlignmentPatternPositions(int version, uint8_t result[7]);static void fillRectangle(int left, int top, int width, int height, uint8_t qrcode[]);
static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[]);static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], enum qrcodegen_Mask mask);static long getPenaltyScore(const uint8_t qrcode[]);static int finderPenaltyCountPatterns(const int runHistory[7], int qrsize);static int finderPenaltyTerminateAndCount(bool currentRunColor, int currentRunLength, int runHistory[7], int qrsize);static void finderPenaltyAddHistory(int currentRunLength, int runHistory[7], int qrsize);
testable bool getModuleBounded(const uint8_t qrcode[], int x, int y);testable void setModuleBounded(uint8_t qrcode[], int x, int y, bool isDark);testable void setModuleUnbounded(uint8_t qrcode[], int x, int y, bool isDark);static bool getBit(int x, int i);
testable int calcSegmentBitLength(enum qrcodegen_Mode mode, size_t numChars);testable int getTotalBits(const struct qrcodegen_Segment segs[], size_t len, int version);static int numCharCountBits(enum qrcodegen_Mode mode, int version);
/*---- Private tables of constants ----*/
// The set of all legal characters in alphanumeric mode, where each character// value maps to the index in the string. For checking text and encoding segments.static const char *ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
// Sentinel value for use in only some functions.#define LENGTH_OVERFLOW -1
// For generating error correction codes.testable const int8_t ECC_CODEWORDS_PER_BLOCK[4][41] = { // Version: (note that index 0 is for padding, and is set to an illegal value) //0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 Error correction level {-1, 7, 10, 15, 20, 26, 18, 20, 24, 30, 18, 20, 24, 26, 30, 22, 24, 28, 30, 28, 28, 28, 28, 30, 30, 26, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // Low {-1, 10, 16, 26, 18, 24, 16, 18, 22, 22, 26, 30, 22, 22, 24, 24, 28, 28, 26, 26, 26, 26, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28}, // Medium {-1, 13, 22, 18, 26, 18, 24, 18, 22, 20, 24, 28, 26, 24, 20, 30, 24, 28, 28, 26, 30, 28, 30, 30, 30, 30, 28, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // Quartile {-1, 17, 28, 22, 16, 22, 28, 26, 26, 24, 28, 24, 28, 22, 24, 24, 30, 28, 28, 26, 28, 30, 24, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30}, // High};
#define qrcodegen_REED_SOLOMON_DEGREE_MAX 30 // Based on the table above
// For generating error correction codes.testable const int8_t NUM_ERROR_CORRECTION_BLOCKS[4][41] = { // Version: (note that index 0 is for padding, and is set to an illegal value) //0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 Error correction level {-1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 4, 4, 4, 4, 4, 6, 6, 6, 6, 7, 8, 8, 9, 9, 10, 12, 12, 12, 13, 14, 15, 16, 17, 18, 19, 19, 20, 21, 22, 24, 25}, // Low {-1, 1, 1, 1, 2, 2, 4, 4, 4, 5, 5, 5, 8, 9, 9, 10, 10, 11, 13, 14, 16, 17, 17, 18, 20, 21, 23, 25, 26, 28, 29, 31, 33, 35, 37, 38, 40, 43, 45, 47, 49}, // Medium {-1, 1, 1, 2, 2, 4, 4, 6, 6, 8, 8, 8, 10, 12, 16, 12, 17, 16, 18, 21, 20, 23, 23, 25, 27, 29, 34, 34, 35, 38, 40, 43, 45, 48, 51, 53, 56, 59, 62, 65, 68}, // Quartile {-1, 1, 1, 2, 4, 4, 4, 5, 6, 8, 8, 11, 11, 16, 16, 18, 16, 19, 21, 25, 25, 25, 34, 30, 32, 35, 37, 40, 42, 45, 48, 51, 54, 57, 60, 63, 66, 70, 74, 77, 81}, // High};
// For automatic mask pattern selection.static const int PENALTY_N1 = 3;static const int PENALTY_N2 = 3;static const int PENALTY_N3 = 40;static const int PENALTY_N4 = 10;
/*---- High-level QR Code encoding functions ----*/
// Public function - see documentation comment in header file.bool qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[], enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl) { size_t textLen = strlen(text); if (textLen == 0) return qrcodegen_encodeSegmentsAdvanced(NULL, 0, ecl, minVersion, maxVersion, mask, boostEcl, tempBuffer, qrcode); size_t bufLen = (size_t)qrcodegen_BUFFER_LEN_FOR_VERSION(maxVersion); struct qrcodegen_Segment seg; if (qrcodegen_isNumeric(text)) { if (qrcodegen_calcSegmentBufferSize(qrcodegen_Mode_NUMERIC, textLen) > bufLen) goto fail; seg = qrcodegen_makeNumeric(text, tempBuffer); } else if (qrcodegen_isAlphanumeric(text)) { if (qrcodegen_calcSegmentBufferSize(qrcodegen_Mode_ALPHANUMERIC, textLen) > bufLen) goto fail; seg = qrcodegen_makeAlphanumeric(text, tempBuffer); } else { if (textLen > bufLen) goto fail; for (size_t i = 0; i < textLen; i++) tempBuffer[i] = (uint8_t)text[i]; seg.mode = qrcodegen_Mode_BYTE; seg.bitLength = calcSegmentBitLength(seg.mode, textLen); if (seg.bitLength == LENGTH_OVERFLOW) goto fail; seg.numChars = (int)textLen; seg.data = tempBuffer; } return qrcodegen_encodeSegmentsAdvanced(&seg, 1, ecl, minVersion, maxVersion, mask, boostEcl, tempBuffer, qrcode); fail: qrcode[0] = 0; // Set size to invalid value for safety return false;}
// Public function - see documentation comment in header file.bool 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) { struct qrcodegen_Segment seg; seg.mode = qrcodegen_Mode_BYTE; seg.bitLength = calcSegmentBitLength(seg.mode, dataLen); if (seg.bitLength == LENGTH_OVERFLOW) { qrcode[0] = 0; // Set size to invalid value for safety return false; } seg.numChars = (int)dataLen; seg.data = dataAndTemp; return qrcodegen_encodeSegmentsAdvanced(&seg, 1, ecl, minVersion, maxVersion, mask, boostEcl, dataAndTemp, qrcode);}
// Appends the given number of low-order bits of the given value to the given byte-based// bit buffer, increasing the bit length. Requires 0 <= numBits <= 16 and val < 2^numBits.testable void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[], int *bitLen) { assert(0 <= numBits && numBits <= 16 && (unsigned long)val >> numBits == 0); for (int i = numBits - 1; i >= 0; i--, (*bitLen)++) buffer[*bitLen >> 3] |= ((val >> i) & 1) << (7 - (*bitLen & 7));}
/*---- Low-level QR Code encoding functions ----*/
// Public function - see documentation comment in header file.bool qrcodegen_encodeSegments(const struct qrcodegen_Segment segs[], size_t len, enum qrcodegen_Ecc ecl, uint8_t tempBuffer[], uint8_t qrcode[]) { return qrcodegen_encodeSegmentsAdvanced(segs, len, ecl, qrcodegen_VERSION_MIN, qrcodegen_VERSION_MAX, qrcodegen_Mask_AUTO, true, tempBuffer, qrcode);}
// Public function - see documentation comment in header file.bool qrcodegen_encodeSegmentsAdvanced(const struct qrcodegen_Segment segs[], size_t len, enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl, uint8_t tempBuffer[], uint8_t qrcode[]) { assert(segs != NULL || len == 0); assert(qrcodegen_VERSION_MIN <= minVersion && minVersion <= maxVersion && maxVersion <= qrcodegen_VERSION_MAX); assert(0 <= (int)ecl && (int)ecl <= 3 && -1 <= (int)mask && (int)mask <= 7); // Find the minimal version number to use int version, dataUsedBits; for (version = minVersion; ; version++) { int dataCapacityBits = getNumDataCodewords(version, ecl) * 8; // Number of data bits available dataUsedBits = getTotalBits(segs, len, version); if (dataUsedBits != LENGTH_OVERFLOW && dataUsedBits <= dataCapacityBits) break; // This version number is found to be suitable if (version >= maxVersion) { // All versions in the range could not fit the given data qrcode[0] = 0; // Set size to invalid value for safety return false; } } assert(dataUsedBits != LENGTH_OVERFLOW); // Increase the error correction level while the data still fits in the current version number for (int i = (int)qrcodegen_Ecc_MEDIUM; i <= (int)qrcodegen_Ecc_HIGH; i++) { // From low to high if (boostEcl && dataUsedBits <= getNumDataCodewords(version, (enum qrcodegen_Ecc)i) * 8) ecl = (enum qrcodegen_Ecc)i; } // Concatenate all segments to create the data bit string memset(qrcode, 0, (size_t)qrcodegen_BUFFER_LEN_FOR_VERSION(version) * sizeof(qrcode[0])); int bitLen = 0; for (size_t i = 0; i < len; i++) { const struct qrcodegen_Segment *seg = &segs[i]; appendBitsToBuffer((unsigned int)seg->mode, 4, qrcode, &bitLen); appendBitsToBuffer((unsigned int)seg->numChars, numCharCountBits(seg->mode, version), qrcode, &bitLen); for (int j = 0; j < seg->bitLength; j++) { int bit = (seg->data[j >> 3] >> (7 - (j & 7))) & 1; appendBitsToBuffer((unsigned int)bit, 1, qrcode, &bitLen); } } assert(bitLen == dataUsedBits); // Add terminator and pad up to a byte if applicable int dataCapacityBits = getNumDataCodewords(version, ecl) * 8; assert(bitLen <= dataCapacityBits); int terminatorBits = dataCapacityBits - bitLen; if (terminatorBits > 4) terminatorBits = 4; appendBitsToBuffer(0, terminatorBits, qrcode, &bitLen); appendBitsToBuffer(0, (8 - bitLen % 8) % 8, qrcode, &bitLen); assert(bitLen % 8 == 0); // Pad with alternating bytes until data capacity is reached for (uint8_t padByte = 0xEC; bitLen < dataCapacityBits; padByte ^= 0xEC ^ 0x11) appendBitsToBuffer(padByte, 8, qrcode, &bitLen); // Compute ECC, draw modules addEccAndInterleave(qrcode, version, ecl, tempBuffer); initializeFunctionModules(version, qrcode); drawCodewords(tempBuffer, getNumRawDataModules(version) / 8, qrcode); drawLightFunctionModules(qrcode, version); initializeFunctionModules(version, tempBuffer); // Do masking if (mask == qrcodegen_Mask_AUTO) { // Automatically choose best mask long minPenalty = LONG_MAX; for (int i = 0; i < 8; i++) { enum qrcodegen_Mask msk = (enum qrcodegen_Mask)i; applyMask(tempBuffer, qrcode, msk); drawFormatBits(ecl, msk, qrcode); long penalty = getPenaltyScore(qrcode); if (penalty < minPenalty) { mask = msk; minPenalty = penalty; } applyMask(tempBuffer, qrcode, msk); // Undoes the mask due to XOR } } assert(0 <= (int)mask && (int)mask <= 7); applyMask(tempBuffer, qrcode, mask); // Apply the final choice of mask drawFormatBits(ecl, mask, qrcode); // Overwrite old format bits return true;}
/*---- 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 : dataLen] contains// the input data. data[dataLen : rawCodewords] is used as a temporary work area and will// be clobbered by this function. The final answer is stored in result[0 : rawCodewords].testable void addEccAndInterleave(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 = getNumDataCodewords(version, ecl); int numShortBlocks = numBlocks - rawCodewords % numBlocks; int shortBlockDataLen = rawCodewords / numBlocks - blockEccLen; // Split data into blocks, calculate ECC, and interleave // (not concatenate) the bytes into a single sequence uint8_t rsdiv[qrcodegen_REED_SOLOMON_DEGREE_MAX]; reedSolomonComputeDivisor(blockEccLen, rsdiv); const uint8_t *dat = data; for (int i = 0; i < numBlocks; i++) { int datLen = shortBlockDataLen + (i < numShortBlocks ? 0 : 1); uint8_t *ecc = &data[dataLen]; // Temporary storage reedSolomonComputeRemainder(dat, datLen, rsdiv, blockEccLen, ecc); for (int j = 0, k = i; j < datLen; j++, k += numBlocks) { // Copy data if (j == shortBlockDataLen) k -= numShortBlocks; result[k] = dat[j]; } for (int j = 0, k = dataLen + i; j < blockEccLen; j++, k += numBlocks) // Copy ECC result[k] = ecc[j]; dat += datLen; }}
// 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].testable int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl) { int v = version, e = (int)ecl; assert(0 <= e && e < 4); return getNumRawDataModules(v) / 8 - ECC_CODEWORDS_PER_BLOCK [e][v] * NUM_ERROR_CORRECTION_BLOCKS[e][v];}
// 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]. This could be implemented as a 40-entry lookup table.testable int getNumRawDataModules(int ver) { assert(qrcodegen_VERSION_MIN <= ver && ver <= qrcodegen_VERSION_MAX); int result = (16 * ver + 128) * ver + 64; if (ver >= 2) { int numAlign = ver / 7 + 2; result -= (25 * numAlign - 10) * numAlign - 55; if (ver >= 7) result -= 36; } assert(208 <= result && result <= 29648); return result;}
/*---- Reed-Solomon ECC generator functions ----*/
// Computes a Reed-Solomon ECC generator polynomial for the given degree, storing in result[0 : degree].// This could be implemented as a lookup table over all possible parameter values, instead of as an algorithm.testable void reedSolomonComputeDivisor(int degree, uint8_t result[]) { assert(1 <= degree && degree <= qrcodegen_REED_SOLOMON_DEGREE_MAX); // 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}. memset(result, 0, (size_t)degree * sizeof(result[0])); result[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}), // 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 (int j = 0; j < degree; j++) { result[j] = reedSolomonMultiply(result[j], root); if (j + 1 < degree) result[j] ^= result[j + 1]; } root = reedSolomonMultiply(root, 0x02); }}
// Computes the Reed-Solomon error correction codeword for the given data and divisor polynomials.// The remainder when data[0 : dataLen] is divided by divisor[0 : degree] is stored in result[0 : degree].// All polynomials are in big endian, and the generator has an implicit leading 1 term.testable void reedSolomonComputeRemainder(const uint8_t data[], int dataLen, const uint8_t generator[], int degree, uint8_t result[]) { assert(1 <= degree && degree <= qrcodegen_REED_SOLOMON_DEGREE_MAX); memset(result, 0, (size_t)degree * sizeof(result[0])); for (int i = 0; i < dataLen; i++) { // Polynomial division uint8_t factor = data[i] ^ result[0]; memmove(&result[0], &result[1], (size_t)(degree - 1) * sizeof(result[0])); result[degree - 1] = 0; for (int j = 0; j < degree; j++) result[j] ^= reedSolomonMultiply(generator[j], factor); }}
#undef qrcodegen_REED_SOLOMON_DEGREE_MAX
// Returns the product of the two given field elements modulo GF(2^8/0x11D).// All inputs are valid. This could be implemented as a 256*256 lookup table.testable uint8_t reedSolomonMultiply(uint8_t x, uint8_t y) { // Russian peasant multiplication uint8_t z = 0; for (int i = 7; i >= 0; i--) { z = (uint8_t)((z << 1) ^ ((z >> 7) * 0x11D)); z ^= ((y >> i) & 1) * x; } return z;}
/*---- Drawing function modules ----*/
// Clears the given QR Code grid with light modules for the given// version's size, then marks every function module as dark.testable void initializeFunctionModules(int version, uint8_t qrcode[]) { // Initialize QR Code int qrsize = version * 4 + 17; memset(qrcode, 0, (size_t)((qrsize * qrsize + 7) / 8 + 1) * sizeof(qrcode[0])); qrcode[0] = (uint8_t)qrsize; // Fill horizontal and vertical timing patterns fillRectangle(6, 0, 1, qrsize, qrcode); fillRectangle(0, 6, qrsize, 1, qrcode); // Fill 3 finder patterns (all corners except bottom right) and format bits fillRectangle(0, 0, 9, 9, qrcode); fillRectangle(qrsize - 8, 0, 8, 9, qrcode); fillRectangle(0, qrsize - 8, 9, 8, qrcode); // Fill numerous alignment patterns uint8_t alignPatPos[7]; int numAlign = getAlignmentPatternPositions(version, alignPatPos); for (int i = 0; i < numAlign; i++) { for (int j = 0; j < numAlign; j++) { // Don't draw on the three finder corners if (!((i == 0 && j == 0) || (i == 0 && j == numAlign - 1) || (i == numAlign - 1 && j == 0))) fillRectangle(alignPatPos[i] - 2, alignPatPos[j] - 2, 5, 5, qrcode); } } // Fill version blocks if (version >= 7) { fillRectangle(qrsize - 11, 0, 3, 6, qrcode); fillRectangle(0, qrsize - 11, 6, 3, qrcode); }}
// Draws light function modules and possibly some dark modules onto the given QR Code, without changing// non-function modules. This does not draw the format bits. This requires all function modules to be previously// marked dark (namely by initializeFunctionModules()), because this may skip redrawing dark function modules.static void drawLightFunctionModules(uint8_t qrcode[], int version) { // Draw horizontal and vertical timing patterns int qrsize = qrcodegen_getSize(qrcode); for (int i = 7; i < qrsize - 7; i += 2) { setModuleBounded(qrcode, 6, i, false); setModuleBounded(qrcode, i, 6, false); } // Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules) for (int dy = -4; dy <= 4; dy++) { for (int dx = -4; dx <= 4; dx++) { int dist = abs(dx); if (abs(dy) > dist) dist = abs(dy); if (dist == 2 || dist == 4) { setModuleUnbounded(qrcode, 3 + dx, 3 + dy, false); setModuleUnbounded(qrcode, qrsize - 4 + dx, 3 + dy, false); setModuleUnbounded(qrcode, 3 + dx, qrsize - 4 + dy, false); } } } // Draw numerous alignment patterns uint8_t alignPatPos[7]; int numAlign = getAlignmentPatternPositions(version, alignPatPos); for (int i = 0; i < numAlign; i++) { for (int j = 0; j < numAlign; j++) { if ((i == 0 && j == 0) || (i == 0 && j == numAlign - 1) || (i == numAlign - 1 && j == 0)) continue; // Don't draw on the three finder corners for (int dy = -1; dy <= 1; dy++) { for (int dx = -1; dx <= 1; dx++) setModuleBounded(qrcode, alignPatPos[i] + dx, alignPatPos[j] + dy, dx == 0 && dy == 0); } } } // Draw version blocks if (version >= 7) { // Calculate error correction code and pack bits int rem = version; // version is uint6, in the range [7, 40] for (int i = 0; i < 12; i++) rem = (rem << 1) ^ ((rem >> 11) * 0x1F25); long bits = (long)version << 12 | rem; // uint18 assert(bits >> 18 == 0); // Draw two copies for (int i = 0; i < 6; i++) { for (int j = 0; j < 3; j++) { int k = qrsize - 11 + j; setModuleBounded(qrcode, k, i, (bits & 1) != 0); setModuleBounded(qrcode, i, k, (bits & 1) != 0); bits >>= 1; } } }}
// Draws two copies of the format bits (with its own error correction code) based// on the given mask and error correction level. This always draws all modules of// the format bits, unlike drawLightFunctionModules() which might skip dark modules.static void drawFormatBits(enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, uint8_t qrcode[]) { // Calculate error correction code and pack bits assert(0 <= (int)mask && (int)mask <= 7); static const int table[] = {1, 0, 3, 2}; int data = table[(int)ecl] << 3 | (int)mask; // errCorrLvl is uint2, mask is uint3 int rem = data; for (int i = 0; i < 10; i++) rem = (rem << 1) ^ ((rem >> 9) * 0x537); int bits = (data << 10 | rem) ^ 0x5412; // uint15 assert(bits >> 15 == 0); // Draw first copy for (int i = 0; i <= 5; i++) setModuleBounded(qrcode, 8, i, getBit(bits, i)); setModuleBounded(qrcode, 8, 7, getBit(bits, 6)); setModuleBounded(qrcode, 8, 8, getBit(bits, 7)); setModuleBounded(qrcode, 7, 8, getBit(bits, 8)); for (int i = 9; i < 15; i++) setModuleBounded(qrcode, 14 - i, 8, getBit(bits, i)); // Draw second copy int qrsize = qrcodegen_getSize(qrcode); for (int i = 0; i < 8; i++) setModuleBounded(qrcode, qrsize - 1 - i, 8, getBit(bits, i)); for (int i = 8; i < 15; i++) setModuleBounded(qrcode, 8, qrsize - 15 + i, getBit(bits, i)); setModuleBounded(qrcode, 8, qrsize - 8, true); // Always dark}
// Calculates and stores an ascending list of positions of alignment patterns// for this version number, returning the length of the list (in the range [0,7]).// Each position is in the range [0,177), and are used on both the x and y axes.// This could be implemented as lookup table of 40 variable-length lists of unsigned bytes.testable int getAlignmentPatternPositions(int version, uint8_t result[7]) { if (version == 1) return 0; int numAlign = version / 7 + 2; int step = (version * 8 + numAlign * 3 + 5) / (numAlign * 4 - 4) * 2; for (int i = numAlign - 1, pos = version * 4 + 10; i >= 1; i--, pos -= step) result[i] = (uint8_t)pos; result[0] = 6; return numAlign;}
// Sets every module in the range [left : left + width] * [top : top + height] to dark.static void fillRectangle(int left, int top, int width, int height, uint8_t qrcode[]) { for (int dy = 0; dy < height; dy++) { for (int dx = 0; dx < width; dx++) setModuleBounded(qrcode, left + dx, top + dy, true); }}
/*---- 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 dark at function modules and light at codeword modules (including unused remainder bits).static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[]) { int qrsize = qrcodegen_getSize(qrcode); int i = 0; // Bit index into the data // Do the funny zigzag scan for (int right = qrsize - 1; right >= 1; right -= 2) { // Index of right column in each column pair if (right == 6) right = 5; for (int vert = 0; vert < qrsize; vert++) { // Vertical counter for (int j = 0; j < 2; j++) { int x = right - j; // Actual x coordinate bool upward = ((right + 1) & 2) == 0; int y = upward ? qrsize - 1 - vert : vert; // Actual y coordinate if (!getModuleBounded(qrcode, x, y) && i < dataLen * 8) { bool dark = getBit(data[i >> 3], 7 - (i & 7)); setModuleBounded(qrcode, x, y, dark); i++; } // If this QR Code has any remainder bits (0 to 7), they were assigned as // 0/false/light by the constructor and are left unchanged by this method } } } assert(i == dataLen * 8);}
// XORs the codeword modules in this QR Code with the given mask pattern// and given pattern of function modules. The codeword bits must be drawn// before masking. Due to the arithmetic of XOR, calling applyMask() with// the same mask value a second time will undo the mask. A final well-formed// QR Code needs exactly one (not zero, two, etc.) mask applied.static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], enum qrcodegen_Mask mask) { assert(0 <= (int)mask && (int)mask <= 7); // Disallows qrcodegen_Mask_AUTO int qrsize = qrcodegen_getSize(qrcode); for (int y = 0; y < qrsize; y++) { for (int x = 0; x < qrsize; x++) { if (getModuleBounded(functionModules, x, y)) continue; bool invert; switch ((int)mask) { case 0: invert = (x + y) % 2 == 0; break; case 1: invert = y % 2 == 0; break; case 2: invert = x % 3 == 0; break; case 3: invert = (x + y) % 3 == 0; break; case 4: invert = (x / 3 + y / 2) % 2 == 0; break; case 5: invert = x * y % 2 + x * y % 3 == 0; break; case 6: invert = (x * y % 2 + x * y % 3) % 2 == 0; break; case 7: invert = ((x + y) % 2 + x * y % 3) % 2 == 0; break; default: assert(false); return; } bool val = getModuleBounded(qrcode, x, y); setModuleBounded(qrcode, x, y, val ^ invert); } }}
// 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 = qrcodegen_getSize(qrcode); long result = 0; // Adjacent modules in row having same color, and finder-like patterns for (int y = 0; y < qrsize; y++) { bool runColor = false; int runX = 0; int runHistory[7] = {0}; for (int x = 0; x < qrsize; x++) { if (getModuleBounded(qrcode, x, y) == runColor) { runX++; if (runX == 5) result += PENALTY_N1; else if (runX > 5) result++; } else { finderPenaltyAddHistory(runX, runHistory, qrsize); if (!runColor) result += finderPenaltyCountPatterns(runHistory, qrsize) * PENALTY_N3; runColor = getModuleBounded(qrcode, x, y); runX = 1; } } result += finderPenaltyTerminateAndCount(runColor, runX, runHistory, qrsize) * PENALTY_N3; } // Adjacent modules in column having same color, and finder-like patterns for (int x = 0; x < qrsize; x++) { bool runColor = false; int runY = 0; int runHistory[7] = {0}; for (int y = 0; y < qrsize; y++) { if (getModuleBounded(qrcode, x, y) == runColor) { runY++; if (runY == 5) result += PENALTY_N1; else if (runY > 5) result++; } else { finderPenaltyAddHistory(runY, runHistory, qrsize); if (!runColor) result += finderPenaltyCountPatterns(runHistory, qrsize) * PENALTY_N3; runColor = getModuleBounded(qrcode, x, y); runY = 1; } } result += finderPenaltyTerminateAndCount(runColor, runY, runHistory, qrsize) * PENALTY_N3; } // 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 = getModuleBounded(qrcode, x, y); if ( color == getModuleBounded(qrcode, x + 1, y) && color == getModuleBounded(qrcode, x, y + 1) && color == getModuleBounded(qrcode, x + 1, y + 1)) result += PENALTY_N2; } } // Balance of dark and light modules int dark = 0; for (int y = 0; y < qrsize; y++) { for (int x = 0; x < qrsize; x++) { if (getModuleBounded(qrcode, x, y)) dark++; } } int total = qrsize * qrsize; // Note that size is odd, so dark/total != 1/2 // Compute the smallest integer k >= 0 such that (45-5k)% <= dark/total <= (55+5k)% int k = (int)((labs(dark * 20L - total * 10L) + total - 1) / total) - 1; assert(0 <= k && k <= 9); result += k * PENALTY_N4; assert(0 <= result && result <= 2568888L); // Non-tight upper bound based on default values of PENALTY_N1, ..., N4 return result;}
// Can only be called immediately after a light run is added, and// returns either 0, 1, or 2. A helper function for getPenaltyScore().static int finderPenaltyCountPatterns(const int runHistory[7], int qrsize) { int n = runHistory[1]; assert(n <= qrsize * 3); (void)qrsize; bool core = n > 0 && runHistory[2] == n && runHistory[3] == n * 3 && runHistory[4] == n && runHistory[5] == n; // The maximum QR Code size is 177, hence the dark run length n <= 177. // Arithmetic is promoted to int, so n*4 will not overflow. return (core && runHistory[0] >= n * 4 && runHistory[6] >= n ? 1 : 0) + (core && runHistory[6] >= n * 4 && runHistory[0] >= n ? 1 : 0);}
// Must be called at the end of a line (row or column) of modules. A helper function for getPenaltyScore().static int finderPenaltyTerminateAndCount(bool currentRunColor, int currentRunLength, int runHistory[7], int qrsize) { if (currentRunColor) { // Terminate dark run finderPenaltyAddHistory(currentRunLength, runHistory, qrsize); currentRunLength = 0; } currentRunLength += qrsize; // Add light border to final run finderPenaltyAddHistory(currentRunLength, runHistory, qrsize); return finderPenaltyCountPatterns(runHistory, qrsize);}
// Pushes the given value to the front and drops the last value. A helper function for getPenaltyScore().static void finderPenaltyAddHistory(int currentRunLength, int runHistory[7], int qrsize) { if (runHistory[0] == 0) currentRunLength += qrsize; // Add light border to initial run memmove(&runHistory[1], &runHistory[0], 6 * sizeof(runHistory[0])); runHistory[0] = currentRunLength;}
/*---- Basic QR Code information ----*/
// Public function - see documentation comment in header file.int qrcodegen_getSize(const uint8_t qrcode[]) { assert(qrcode != NULL); int result = qrcode[0]; assert((qrcodegen_VERSION_MIN * 4 + 17) <= result && result <= (qrcodegen_VERSION_MAX * 4 + 17)); return result;}
// Public function - see documentation comment in header file.bool qrcodegen_getModule(const uint8_t qrcode[], int x, int y) { assert(qrcode != NULL); int qrsize = qrcode[0]; return (0 <= x && x < qrsize && 0 <= y && y < qrsize) && getModuleBounded(qrcode, x, y);}
// Returns the color of the module at the given coordinates, which must be in bounds.testable bool getModuleBounded(const uint8_t qrcode[], int x, int y) { int qrsize = qrcode[0]; assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize); int index = y * qrsize + x; return getBit(qrcode[(index >> 3) + 1], index & 7);}
// Sets the color of the module at the given coordinates, which must be in bounds.testable void setModuleBounded(uint8_t qrcode[], int x, int y, bool isDark) { int qrsize = qrcode[0]; 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) + 1; if (isDark) qrcode[byteIndex] |= 1 << bitIndex; else qrcode[byteIndex] &= (1 << bitIndex) ^ 0xFF;}
// Sets the color of the module at the given coordinates, doing nothing if out of bounds.testable void setModuleUnbounded(uint8_t qrcode[], int x, int y, bool isDark) { int qrsize = qrcode[0]; if (0 <= x && x < qrsize && 0 <= y && y < qrsize) setModuleBounded(qrcode, x, y, isDark);}
// Returns true iff the i'th bit of x is set to 1. Requires x >= 0 and 0 <= i <= 14.static bool getBit(int x, int i) { return ((x >> i) & 1) != 0;}
/*---- Segment handling ----*/
// Public function - see documentation comment in header file.bool qrcodegen_isNumeric(const char *text) { assert(text != NULL); for (; *text != '\0'; text++) { if (*text < '0' || *text > '9') return false; } return true;}
// Public function - see documentation comment in header file.bool qrcodegen_isAlphanumeric(const char *text) { assert(text != NULL); for (; *text != '\0'; text++) { if (strchr(ALPHANUMERIC_CHARSET, *text) == NULL) return false; } return true;}
// Public function - see documentation comment in header file.size_t qrcodegen_calcSegmentBufferSize(enum qrcodegen_Mode mode, size_t numChars) { int temp = calcSegmentBitLength(mode, numChars); if (temp == LENGTH_OVERFLOW) return SIZE_MAX; assert(0 <= temp && temp <= INT16_MAX); return ((size_t)temp + 7) / 8;}
// Returns the number of data bits needed to represent a segment// containing the given number of characters using the given mode. Notes:// - Returns LENGTH_OVERFLOW on failure, i.e. numChars > INT16_MAX// or the number of needed bits exceeds INT16_MAX (i.e. 32767).// - Otherwise, all valid results are in the range [0, INT16_MAX].// - For byte mode, numChars measures the number of bytes, not Unicode code points.// - For ECI mode, numChars must be 0, and the worst-case number of bits is returned.// An actual ECI segment can have shorter data. For non-ECI modes, the result is exact.testable int calcSegmentBitLength(enum qrcodegen_Mode mode, size_t numChars) { // All calculations are designed to avoid overflow on all platforms if (numChars > (unsigned int)INT16_MAX) return LENGTH_OVERFLOW; long result = (long)numChars; if (mode == qrcodegen_Mode_NUMERIC) result = (result * 10 + 2) / 3; // ceil(10/3 * n) else if (mode == qrcodegen_Mode_ALPHANUMERIC) result = (result * 11 + 1) / 2; // ceil(11/2 * n) else if (mode == qrcodegen_Mode_BYTE) result *= 8; else if (mode == qrcodegen_Mode_KANJI) result *= 13; else if (mode == qrcodegen_Mode_ECI && numChars == 0) result = 3 * 8; else { // Invalid argument assert(false); return LENGTH_OVERFLOW; } assert(result >= 0); if (result > INT16_MAX) return LENGTH_OVERFLOW; return (int)result;}
// Public function - see documentation comment in header file.struct qrcodegen_Segment qrcodegen_makeBytes(const uint8_t data[], size_t len, uint8_t buf[]) { assert(data != NULL || len == 0); struct qrcodegen_Segment result; result.mode = qrcodegen_Mode_BYTE; result.bitLength = calcSegmentBitLength(result.mode, len); assert(result.bitLength != LENGTH_OVERFLOW); result.numChars = (int)len; if (len > 0) memcpy(buf, data, len * sizeof(buf[0])); result.data = buf; return result;}
// Public function - see documentation comment in header file.struct qrcodegen_Segment qrcodegen_makeNumeric(const char *digits, uint8_t buf[]) { assert(digits != NULL); struct qrcodegen_Segment result; size_t len = strlen(digits); result.mode = qrcodegen_Mode_NUMERIC; int bitLen = calcSegmentBitLength(result.mode, len); assert(bitLen != LENGTH_OVERFLOW); result.numChars = (int)len; if (bitLen > 0) memset(buf, 0, ((size_t)bitLen + 7) / 8 * sizeof(buf[0])); result.bitLength = 0; unsigned int accumData = 0; int accumCount = 0; for (; *digits != '\0'; digits++) { char c = *digits; assert('0' <= c && c <= '9'); accumData = accumData * 10 + (unsigned int)(c - '0'); accumCount++; if (accumCount == 3) { appendBitsToBuffer(accumData, 10, buf, &result.bitLength); accumData = 0; accumCount = 0; } } if (accumCount > 0) // 1 or 2 digits remaining appendBitsToBuffer(accumData, accumCount * 3 + 1, buf, &result.bitLength); assert(result.bitLength == bitLen); result.data = buf; return result;}
// Public function - see documentation comment in header file.struct qrcodegen_Segment qrcodegen_makeAlphanumeric(const char *text, uint8_t buf[]) { assert(text != NULL); struct qrcodegen_Segment result; size_t len = strlen(text); result.mode = qrcodegen_Mode_ALPHANUMERIC; int bitLen = calcSegmentBitLength(result.mode, len); assert(bitLen != LENGTH_OVERFLOW); result.numChars = (int)len; if (bitLen > 0) memset(buf, 0, ((size_t)bitLen + 7) / 8 * sizeof(buf[0])); result.bitLength = 0; unsigned int accumData = 0; int accumCount = 0; for (; *text != '\0'; text++) { const char *temp = strchr(ALPHANUMERIC_CHARSET, *text); assert(temp != NULL); accumData = accumData * 45 + (unsigned int)(temp - ALPHANUMERIC_CHARSET); accumCount++; if (accumCount == 2) { appendBitsToBuffer(accumData, 11, buf, &result.bitLength); accumData = 0; accumCount = 0; } } if (accumCount > 0) // 1 character remaining appendBitsToBuffer(accumData, 6, buf, &result.bitLength); assert(result.bitLength == bitLen); result.data = buf; return result;}
// Public function - see documentation comment in header file.struct qrcodegen_Segment qrcodegen_makeEci(long assignVal, uint8_t buf[]) { struct qrcodegen_Segment result; result.mode = qrcodegen_Mode_ECI; result.numChars = 0; result.bitLength = 0; if (assignVal < 0) assert(false); else if (assignVal < (1 << 7)) { memset(buf, 0, 1 * sizeof(buf[0])); appendBitsToBuffer((unsigned int)assignVal, 8, buf, &result.bitLength); } else if (assignVal < (1 << 14)) { memset(buf, 0, 2 * sizeof(buf[0])); appendBitsToBuffer(2, 2, buf, &result.bitLength); appendBitsToBuffer((unsigned int)assignVal, 14, buf, &result.bitLength); } else if (assignVal < 1000000L) { memset(buf, 0, 3 * sizeof(buf[0])); appendBitsToBuffer(6, 3, buf, &result.bitLength); appendBitsToBuffer((unsigned int)(assignVal >> 10), 11, buf, &result.bitLength); appendBitsToBuffer((unsigned int)(assignVal & 0x3FF), 10, buf, &result.bitLength); } else assert(false); result.data = buf; return result;}
// Calculates the number of bits needed to encode the given segments at the given version.// Returns a non-negative number if successful. Otherwise returns LENGTH_OVERFLOW if a segment// has too many characters to fit its length field, or the total bits exceeds INT16_MAX.testable int getTotalBits(const struct qrcodegen_Segment segs[], size_t len, int version) { assert(segs != NULL || len == 0); long result = 0; for (size_t i = 0; i < len; i++) { int numChars = segs[i].numChars; int bitLength = segs[i].bitLength; assert(0 <= numChars && numChars <= INT16_MAX); assert(0 <= bitLength && bitLength <= INT16_MAX); int ccbits = numCharCountBits(segs[i].mode, version); assert(0 <= ccbits && ccbits <= 16); if (numChars >= (1L << ccbits)) return LENGTH_OVERFLOW; // The segment's length doesn't fit the field's bit width result += 4L + ccbits + bitLength; if (result > INT16_MAX) return LENGTH_OVERFLOW; // The sum might overflow an int type } assert(0 <= result && result <= INT16_MAX); return (int)result;}
// Returns the bit width of the character count field for a segment in the given mode// in a QR Code at the given version number. The result is in the range [0, 16].static int numCharCountBits(enum qrcodegen_Mode mode, int version) { assert(qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX); int i = (version + 7) / 17; switch (mode) { case qrcodegen_Mode_NUMERIC : { static const int temp[] = {10, 12, 14}; return temp[i]; } case qrcodegen_Mode_ALPHANUMERIC: { static const int temp[] = { 9, 11, 13}; return temp[i]; } case qrcodegen_Mode_BYTE : { static const int temp[] = { 8, 16, 16}; return temp[i]; } case qrcodegen_Mode_KANJI : { static const int temp[] = { 8, 10, 12}; return temp[i]; } case qrcodegen_Mode_ECI : return 0; default: assert(false); return -1; // Dummy value }}
#undef LENGTH_OVERFLOW