1 /*
2 * QR Code generator library (C)
3 *
4 * Copyright (c) Project Nayuki. (MIT License)
5 * https://www.nayuki.io/page/qr-code-generator-library
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy of
8 * this software and associated documentation files (the "Software"), to deal in
9 * the Software without restriction, including without limitation the rights to
10 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
11 * the Software, and to permit persons to whom the Software is furnished to do so,
12 * subject to the following conditions:
13 * - The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 * - The Software is provided "as is", without warranty of any kind, express or
16 * implied, including but not limited to the warranties of merchantability,
17 * fitness for a particular purpose and noninfringement. In no event shall the
18 * authors or copyright holders be liable for any claim, damages or other
19 * liability, whether in an action of contract, tort or otherwise, arising from,
20 * out of or in connection with the Software or the use or other dealings in the
21 * Software.
22 */
23
24 #include <assert.h>
25 #include <limits.h>
26 #include <stdlib.h>
27 #include <string.h>
28 #include "qrcodegen.h"
29
30 #ifndef QRCODEGEN_TEST
31 #define testable static // Keep functions private
32 #else
33 #define testable // Expose private functions
34 #endif
35
36
37 /*---- Forward declarations for private functions ----*/
38
39 // Regarding all public and private functions defined in this source file:
40 // - They require all pointer/array arguments to be not null unless the array length is zero.
41 // - They only read input scalar/array arguments, write to output pointer/array
42 // arguments, and return scalar values; they are "pure" functions.
43 // - They don't read mutable global variables or write to any global variables.
44 // - They don't perform I/O, read the clock, print to console, etc.
45 // - They allocate a small and constant amount of stack memory.
46 // - They don't allocate or free any memory on the heap.
47 // - They don't recurse or mutually recurse. All the code
48 // could be inlined into the top-level public functions.
49 // - They run in at most quadratic time with respect to input arguments.
50 // Most functions run in linear time, and some in constant time.
51 // There are no unbounded loops or non-obvious termination conditions.
52 // - They are completely thread-safe if the caller does not give the
53 // same writable buffer to concurrent calls to these functions.
54
55 testable void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[], int *bitLen);
56
57 testable void addEccAndInterleave(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[]);
58 testable int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl);
59 testable int getNumRawDataModules(int ver);
60
61 testable void calcReedSolomonGenerator(int degree, uint8_t result[]);
62 testable void calcReedSolomonRemainder(const uint8_t data[], int dataLen,
63 const uint8_t generator[], int degree, uint8_t result[]);
64 testable uint8_t finiteFieldMultiply(uint8_t x, uint8_t y);
65
66 testable void initializeFunctionModules(int version, uint8_t qrcode[]);
67 static void drawWhiteFunctionModules(uint8_t qrcode[], int version);
68 static void drawFormatBits(enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, uint8_t qrcode[]);
69 testable int getAlignmentPatternPositions(int version, uint8_t result[7]);
70 static void fillRectangle(int left, int top, int width, int height, uint8_t qrcode[]);
71
72 static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[]);
73 static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], enum qrcodegen_Mask mask);
74 static long getPenaltyScore(const uint8_t qrcode[]);
75 static void addRunToHistory(unsigned char run, unsigned char history[7]);
76 static bool hasFinderLikePattern(const unsigned char runHistory[7]);
77
78 testable bool getModule(const uint8_t qrcode[], int x, int y);
79 testable void setModule(uint8_t qrcode[], int x, int y, bool isBlack);
80 testable void setModuleBounded(uint8_t qrcode[], int x, int y, bool isBlack);
81 static bool getBit(int x, int i);
82
83 testable int calcSegmentBitLength(enum qrcodegen_Mode mode, size_t numChars);
84 testable int getTotalBits(const struct qrcodegen_Segment segs[], size_t len, int version);
85 static int numCharCountBits(enum qrcodegen_Mode mode, int version);
86
87
88
89 /*---- Private tables of constants ----*/
90
91 // The set of all legal characters in alphanumeric mode, where each character
92 // value maps to the index in the string. For checking text and encoding segments.
93 static const char *ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
94
95 // For generating error correction codes.
96 testable const int8_t ECC_CODEWORDS_PER_BLOCK[4][41] = {
97 // Version: (note that index 0 is for padding, and is set to an illegal value)
98 //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
99 {-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
100 {-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
101 {-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
102 {-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
103 };
104
105 #define qrcodegen_REED_SOLOMON_DEGREE_MAX 30 // Based on the table above
106
107 // For generating error correction codes.
108 testable const int8_t NUM_ERROR_CORRECTION_BLOCKS[4][41] = {
109 // Version: (note that index 0 is for padding, and is set to an illegal value)
110 //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
111 {-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
112 {-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
113 {-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
114 {-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
115 };
116
117 // For automatic mask pattern selection.
118 static const int PENALTY_N1 = 3;
119 static const int PENALTY_N2 = 3;
120 static const int PENALTY_N3 = 40;
121 static const int PENALTY_N4 = 10;
122
123
124
125 /*---- High-level QR Code encoding functions ----*/
126
127 // Public function - see documentation comment in header file.
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)128 bool qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[],
129 enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl) {
130
131 size_t textLen = strlen(text);
132 if (textLen == 0)
133 return qrcodegen_encodeSegmentsAdvanced(NULL, 0, ecl, minVersion, maxVersion, mask, boostEcl, tempBuffer, qrcode);
134 size_t bufLen = qrcodegen_BUFFER_LEN_FOR_VERSION(maxVersion);
135
136 struct qrcodegen_Segment seg;
137 if (qrcodegen_isNumeric(text)) {
138 if (qrcodegen_calcSegmentBufferSize(qrcodegen_Mode_NUMERIC, textLen) > bufLen)
139 goto fail;
140 seg = qrcodegen_makeNumeric(text, tempBuffer);
141 } else if (qrcodegen_isAlphanumeric(text)) {
142 if (qrcodegen_calcSegmentBufferSize(qrcodegen_Mode_ALPHANUMERIC, textLen) > bufLen)
143 goto fail;
144 seg = qrcodegen_makeAlphanumeric(text, tempBuffer);
145 } else {
146 if (textLen > bufLen)
147 goto fail;
148 for (size_t i = 0; i < textLen; i++)
149 tempBuffer[i] = (uint8_t)text[i];
150 seg.mode = qrcodegen_Mode_BYTE;
151 seg.bitLength = calcSegmentBitLength(seg.mode, textLen);
152 if (seg.bitLength == -1)
153 goto fail;
154 seg.numChars = (int)textLen;
155 seg.data = tempBuffer;
156 }
157 return qrcodegen_encodeSegmentsAdvanced(&seg, 1, ecl, minVersion, maxVersion, mask, boostEcl, tempBuffer, qrcode);
158
159 fail:
160 qrcode[0] = 0; // Set size to invalid value for safety
161 return false;
162 }
163
164
165 // Public function - see documentation comment in header file.
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)166 bool qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcode[],
167 enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl) {
168
169 struct qrcodegen_Segment seg;
170 seg.mode = qrcodegen_Mode_BYTE;
171 seg.bitLength = calcSegmentBitLength(seg.mode, dataLen);
172 if (seg.bitLength == -1) {
173 qrcode[0] = 0; // Set size to invalid value for safety
174 return false;
175 }
176 seg.numChars = (int)dataLen;
177 seg.data = dataAndTemp;
178 return qrcodegen_encodeSegmentsAdvanced(&seg, 1, ecl, minVersion, maxVersion, mask, boostEcl, dataAndTemp, qrcode);
179 }
180
181
182 // Appends the given number of low-order bits of the given value to the given byte-based
183 // bit buffer, increasing the bit length. Requires 0 <= numBits <= 16 and val < 2^numBits.
appendBitsToBuffer(unsigned int val,int numBits,uint8_t buffer[],int * bitLen)184 testable void appendBitsToBuffer(unsigned int val, int numBits, uint8_t buffer[], int *bitLen) {
185 assert(0 <= numBits && numBits <= 16 && (unsigned long)val >> numBits == 0);
186 for (int i = numBits - 1; i >= 0; i--, (*bitLen)++)
187 buffer[*bitLen >> 3] |= ((val >> i) & 1) << (7 - (*bitLen & 7));
188 }
189
190
191
192 /*---- Low-level QR Code encoding functions ----*/
193
194 // Public function - see documentation comment in header file.
qrcodegen_encodeSegments(const struct qrcodegen_Segment segs[],size_t len,enum qrcodegen_Ecc ecl,uint8_t tempBuffer[],uint8_t qrcode[])195 bool qrcodegen_encodeSegments(const struct qrcodegen_Segment segs[], size_t len,
196 enum qrcodegen_Ecc ecl, uint8_t tempBuffer[], uint8_t qrcode[]) {
197 return qrcodegen_encodeSegmentsAdvanced(segs, len, ecl,
198 qrcodegen_VERSION_MIN, qrcodegen_VERSION_MAX, -1, true, tempBuffer, qrcode);
199 }
200
201
202 // Public function - see documentation comment in header file.
qrcodegen_encodeSegmentsAdvanced(const struct qrcodegen_Segment segs[],size_t len,enum qrcodegen_Ecc ecl,int minVersion,int maxVersion,int mask,bool boostEcl,uint8_t tempBuffer[],uint8_t qrcode[])203 bool qrcodegen_encodeSegmentsAdvanced(const struct qrcodegen_Segment segs[], size_t len, enum qrcodegen_Ecc ecl,
204 int minVersion, int maxVersion, int mask, bool boostEcl, uint8_t tempBuffer[], uint8_t qrcode[]) {
205 assert(segs != NULL || len == 0);
206 assert(qrcodegen_VERSION_MIN <= minVersion && minVersion <= maxVersion && maxVersion <= qrcodegen_VERSION_MAX);
207 assert(0 <= (int)ecl && (int)ecl <= 3 && -1 <= (int)mask && (int)mask <= 7);
208
209 // Find the minimal version number to use
210 int version, dataUsedBits;
211 for (version = minVersion; ; version++) {
212 int dataCapacityBits = getNumDataCodewords(version, ecl) * 8; // Number of data bits available
213 dataUsedBits = getTotalBits(segs, len, version);
214 if (dataUsedBits != -1 && dataUsedBits <= dataCapacityBits)
215 break; // This version number is found to be suitable
216 if (version >= maxVersion) { // All versions in the range could not fit the given data
217 qrcode[0] = 0; // Set size to invalid value for safety
218 return false;
219 }
220 }
221 assert(dataUsedBits != -1);
222
223 // Increase the error correction level while the data still fits in the current version number
224 for (int i = (int)qrcodegen_Ecc_MEDIUM; i <= (int)qrcodegen_Ecc_HIGH; i++) { // From low to high
225 if (boostEcl && dataUsedBits <= getNumDataCodewords(version, (enum qrcodegen_Ecc)i) * 8)
226 ecl = (enum qrcodegen_Ecc)i;
227 }
228
229 // Concatenate all segments to create the data bit string
230 memset(qrcode, 0, qrcodegen_BUFFER_LEN_FOR_VERSION(version) * sizeof(qrcode[0]));
231 int bitLen = 0;
232 for (size_t i = 0; i < len; i++) {
233 const struct qrcodegen_Segment *seg = &segs[i];
234 appendBitsToBuffer((int)seg->mode, 4, qrcode, &bitLen);
235 appendBitsToBuffer(seg->numChars, numCharCountBits(seg->mode, version), qrcode, &bitLen);
236 for (int j = 0; j < seg->bitLength; j++)
237 appendBitsToBuffer((seg->data[j >> 3] >> (7 - (j & 7))) & 1, 1, qrcode, &bitLen);
238 }
239 assert(bitLen == dataUsedBits);
240
241 // Add terminator and pad up to a byte if applicable
242 int dataCapacityBits = getNumDataCodewords(version, ecl) * 8;
243 assert(bitLen <= dataCapacityBits);
244 int terminatorBits = dataCapacityBits - bitLen;
245 if (terminatorBits > 4)
246 terminatorBits = 4;
247 appendBitsToBuffer(0, terminatorBits, qrcode, &bitLen);
248 appendBitsToBuffer(0, (8 - bitLen % 8) % 8, qrcode, &bitLen);
249 assert(bitLen % 8 == 0);
250
251 // Pad with alternating bytes until data capacity is reached
252 for (uint8_t padByte = 0xEC; bitLen < dataCapacityBits; padByte ^= 0xEC ^ 0x11)
253 appendBitsToBuffer(padByte, 8, qrcode, &bitLen);
254
255 // Draw function and data codeword modules
256 addEccAndInterleave(qrcode, version, ecl, tempBuffer);
257 initializeFunctionModules(version, qrcode);
258 drawCodewords(tempBuffer, getNumRawDataModules(version) / 8, qrcode);
259 drawWhiteFunctionModules(qrcode, version);
260 initializeFunctionModules(version, tempBuffer);
261
262 // Handle masking
263 if (mask == qrcodegen_Mask_AUTO) { // Automatically choose best mask
264 long minPenalty = LONG_MAX;
265 for (int i = 0; i < 8; i++) {
266 enum qrcodegen_Mask msk = (enum qrcodegen_Mask)i;
267 applyMask(tempBuffer, qrcode, msk);
268 drawFormatBits(ecl, msk, qrcode);
269 long penalty = getPenaltyScore(qrcode);
270 if (penalty < minPenalty) {
271 mask = msk;
272 minPenalty = penalty;
273 }
274 applyMask(tempBuffer, qrcode, msk); // Undoes the mask due to XOR
275 }
276 }
277 assert(0 <= (int)mask && (int)mask <= 7);
278 applyMask(tempBuffer, qrcode, mask);
279 drawFormatBits(ecl, mask, qrcode);
280 return true;
281 }
282
283
284
285 /*---- Error correction code generation functions ----*/
286
287 // Appends error correction bytes to each block of the given data array, then interleaves
288 // bytes from the blocks and stores them in the result array. data[0 : dataLen] contains
289 // the input data. data[dataLen : rawCodewords] is used as a temporary work area and will
290 // be clobbered by this function. The final answer is stored in result[0 : rawCodewords].
addEccAndInterleave(uint8_t data[],int version,enum qrcodegen_Ecc ecl,uint8_t result[])291 testable void addEccAndInterleave(uint8_t data[], int version, enum qrcodegen_Ecc ecl, uint8_t result[]) {
292 // Calculate parameter numbers
293 assert(0 <= (int)ecl && (int)ecl < 4 && qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
294 int numBlocks = NUM_ERROR_CORRECTION_BLOCKS[(int)ecl][version];
295 int blockEccLen = ECC_CODEWORDS_PER_BLOCK [(int)ecl][version];
296 int rawCodewords = getNumRawDataModules(version) / 8;
297 int dataLen = getNumDataCodewords(version, ecl);
298 int numShortBlocks = numBlocks - rawCodewords % numBlocks;
299 int shortBlockDataLen = rawCodewords / numBlocks - blockEccLen;
300
301 // Split data into blocks, calculate ECC, and interleave
302 // (not concatenate) the bytes into a single sequence
303 uint8_t generator[qrcodegen_REED_SOLOMON_DEGREE_MAX];
304 calcReedSolomonGenerator(blockEccLen, generator);
305 const uint8_t *dat = data;
306 for (int i = 0; i < numBlocks; i++) {
307 int datLen = shortBlockDataLen + (i < numShortBlocks ? 0 : 1);
308 uint8_t *ecc = &data[dataLen]; // Temporary storage
309 calcReedSolomonRemainder(dat, datLen, generator, blockEccLen, ecc);
310 for (int j = 0, k = i; j < datLen; j++, k += numBlocks) { // Copy data
311 if (j == shortBlockDataLen)
312 k -= numShortBlocks;
313 result[k] = dat[j];
314 }
315 for (int j = 0, k = dataLen + i; j < blockEccLen; j++, k += numBlocks) // Copy ECC
316 result[k] = ecc[j];
317 dat += datLen;
318 }
319 }
320
321
322 // Returns the number of 8-bit codewords that can be used for storing data (not ECC),
323 // for the given version number and error correction level. The result is in the range [9, 2956].
getNumDataCodewords(int version,enum qrcodegen_Ecc ecl)324 testable int getNumDataCodewords(int version, enum qrcodegen_Ecc ecl) {
325 int v = version, e = (int)ecl;
326 assert(0 <= e && e < 4);
327 return getNumRawDataModules(v) / 8
328 - ECC_CODEWORDS_PER_BLOCK [e][v]
329 * NUM_ERROR_CORRECTION_BLOCKS[e][v];
330 }
331
332
333 // Returns the number of data bits that can be stored in a QR Code of the given version number, after
334 // all function modules are excluded. This includes remainder bits, so it might not be a multiple of 8.
335 // The result is in the range [208, 29648]. This could be implemented as a 40-entry lookup table.
getNumRawDataModules(int ver)336 testable int getNumRawDataModules(int ver) {
337 assert(qrcodegen_VERSION_MIN <= ver && ver <= qrcodegen_VERSION_MAX);
338 int result = (16 * ver + 128) * ver + 64;
339 if (ver >= 2) {
340 int numAlign = ver / 7 + 2;
341 result -= (25 * numAlign - 10) * numAlign - 55;
342 if (ver >= 7)
343 result -= 36;
344 }
345 return result;
346 }
347
348
349
350 /*---- Reed-Solomon ECC generator functions ----*/
351
352 // Calculates the Reed-Solomon generator polynomial of the given degree, storing in result[0 : degree].
calcReedSolomonGenerator(int degree,uint8_t result[])353 testable void calcReedSolomonGenerator(int degree, uint8_t result[]) {
354 // Start with the monomial x^0
355 assert(1 <= degree && degree <= qrcodegen_REED_SOLOMON_DEGREE_MAX);
356 memset(result, 0, degree * sizeof(result[0]));
357 result[degree - 1] = 1;
358
359 // Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}),
360 // drop the highest term, and store the rest of the coefficients in order of descending powers.
361 // Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D).
362 uint8_t root = 1;
363 for (int i = 0; i < degree; i++) {
364 // Multiply the current product by (x - r^i)
365 for (int j = 0; j < degree; j++) {
366 result[j] = finiteFieldMultiply(result[j], root);
367 if (j + 1 < degree)
368 result[j] ^= result[j + 1];
369 }
370 root = finiteFieldMultiply(root, 0x02);
371 }
372 }
373
374
375 // Calculates the remainder of the polynomial data[0 : dataLen] when divided by the generator[0 : degree], where all
376 // polynomials are in big endian and the generator has an implicit leading 1 term, storing the result in result[0 : degree].
calcReedSolomonRemainder(const uint8_t data[],int dataLen,const uint8_t generator[],int degree,uint8_t result[])377 testable void calcReedSolomonRemainder(const uint8_t data[], int dataLen,
378 const uint8_t generator[], int degree, uint8_t result[]) {
379
380 // Perform polynomial division
381 assert(1 <= degree && degree <= qrcodegen_REED_SOLOMON_DEGREE_MAX);
382 memset(result, 0, degree * sizeof(result[0]));
383 for (int i = 0; i < dataLen; i++) {
384 uint8_t factor = data[i] ^ result[0];
385 memmove(&result[0], &result[1], (degree - 1) * sizeof(result[0]));
386 result[degree - 1] = 0;
387 for (int j = 0; j < degree; j++)
388 result[j] ^= finiteFieldMultiply(generator[j], factor);
389 }
390 }
391
392 #undef qrcodegen_REED_SOLOMON_DEGREE_MAX
393
394
395 // Returns the product of the two given field elements modulo GF(2^8/0x11D).
396 // All inputs are valid. This could be implemented as a 256*256 lookup table.
finiteFieldMultiply(uint8_t x,uint8_t y)397 testable uint8_t finiteFieldMultiply(uint8_t x, uint8_t y) {
398 // Russian peasant multiplication
399 uint8_t z = 0;
400 for (int i = 7; i >= 0; i--) {
401 z = (z << 1) ^ ((z >> 7) * 0x11D);
402 z ^= ((y >> i) & 1) * x;
403 }
404 return z;
405 }
406
407
408
409 /*---- Drawing function modules ----*/
410
411 // Clears the given QR Code grid with white modules for the given
412 // version's size, then marks every function module as black.
initializeFunctionModules(int version,uint8_t qrcode[])413 testable void initializeFunctionModules(int version, uint8_t qrcode[]) {
414 // Initialize QR Code
415 int qrsize = version * 4 + 17;
416 memset(qrcode, 0, ((qrsize * qrsize + 7) / 8 + 1) * sizeof(qrcode[0]));
417 qrcode[0] = (uint8_t)qrsize;
418
419 // Fill horizontal and vertical timing patterns
420 fillRectangle(6, 0, 1, qrsize, qrcode);
421 fillRectangle(0, 6, qrsize, 1, qrcode);
422
423 // Fill 3 finder patterns (all corners except bottom right) and format bits
424 fillRectangle(0, 0, 9, 9, qrcode);
425 fillRectangle(qrsize - 8, 0, 8, 9, qrcode);
426 fillRectangle(0, qrsize - 8, 9, 8, qrcode);
427
428 // Fill numerous alignment patterns
429 uint8_t alignPatPos[7];
430 int numAlign = getAlignmentPatternPositions(version, alignPatPos);
431 for (int i = 0; i < numAlign; i++) {
432 for (int j = 0; j < numAlign; j++) {
433 // Don't draw on the three finder corners
434 if (!((i == 0 && j == 0) || (i == 0 && j == numAlign - 1) || (i == numAlign - 1 && j == 0)))
435 fillRectangle(alignPatPos[i] - 2, alignPatPos[j] - 2, 5, 5, qrcode);
436 }
437 }
438
439 // Fill version blocks
440 if (version >= 7) {
441 fillRectangle(qrsize - 11, 0, 3, 6, qrcode);
442 fillRectangle(0, qrsize - 11, 6, 3, qrcode);
443 }
444 }
445
446
447 // Draws white function modules and possibly some black modules onto the given QR Code, without changing
448 // non-function modules. This does not draw the format bits. This requires all function modules to be previously
449 // marked black (namely by initializeFunctionModules()), because this may skip redrawing black function modules.
drawWhiteFunctionModules(uint8_t qrcode[],int version)450 static void drawWhiteFunctionModules(uint8_t qrcode[], int version) {
451 // Draw horizontal and vertical timing patterns
452 int qrsize = qrcodegen_getSize(qrcode);
453 for (int i = 7; i < qrsize - 7; i += 2) {
454 setModule(qrcode, 6, i, false);
455 setModule(qrcode, i, 6, false);
456 }
457
458 // Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules)
459 for (int dy = -4; dy <= 4; dy++) {
460 for (int dx = -4; dx <= 4; dx++) {
461 int dist = abs(dx);
462 if (abs(dy) > dist)
463 dist = abs(dy);
464 if (dist == 2 || dist == 4) {
465 setModuleBounded(qrcode, 3 + dx, 3 + dy, false);
466 setModuleBounded(qrcode, qrsize - 4 + dx, 3 + dy, false);
467 setModuleBounded(qrcode, 3 + dx, qrsize - 4 + dy, false);
468 }
469 }
470 }
471
472 // Draw numerous alignment patterns
473 uint8_t alignPatPos[7];
474 int numAlign = getAlignmentPatternPositions(version, alignPatPos);
475 for (int i = 0; i < numAlign; i++) {
476 for (int j = 0; j < numAlign; j++) {
477 if ((i == 0 && j == 0) || (i == 0 && j == numAlign - 1) || (i == numAlign - 1 && j == 0))
478 continue; // Don't draw on the three finder corners
479 for (int dy = -1; dy <= 1; dy++) {
480 for (int dx = -1; dx <= 1; dx++)
481 setModule(qrcode, alignPatPos[i] + dx, alignPatPos[j] + dy, dx == 0 && dy == 0);
482 }
483 }
484 }
485
486 // Draw version blocks
487 if (version >= 7) {
488 // Calculate error correction code and pack bits
489 int rem = version; // version is uint6, in the range [7, 40]
490 for (int i = 0; i < 12; i++)
491 rem = (rem << 1) ^ ((rem >> 11) * 0x1F25);
492 long bits = (long)version << 12 | rem; // uint18
493 assert(bits >> 18 == 0);
494
495 // Draw two copies
496 for (int i = 0; i < 6; i++) {
497 for (int j = 0; j < 3; j++) {
498 int k = qrsize - 11 + j;
499 setModule(qrcode, k, i, (bits & 1) != 0);
500 setModule(qrcode, i, k, (bits & 1) != 0);
501 bits >>= 1;
502 }
503 }
504 }
505 }
506
507
508 // Draws two copies of the format bits (with its own error correction code) based
509 // on the given mask and error correction level. This always draws all modules of
510 // the format bits, unlike drawWhiteFunctionModules() which might skip black modules.
drawFormatBits(enum qrcodegen_Ecc ecl,enum qrcodegen_Mask mask,uint8_t qrcode[])511 static void drawFormatBits(enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, uint8_t qrcode[]) {
512 // Calculate error correction code and pack bits
513 assert(0 <= (int)mask && (int)mask <= 7);
514 static const int table[] = {1, 0, 3, 2};
515 int data = table[(int)ecl] << 3 | (int)mask; // errCorrLvl is uint2, mask is uint3
516 int rem = data;
517 for (int i = 0; i < 10; i++)
518 rem = (rem << 1) ^ ((rem >> 9) * 0x537);
519 int bits = (data << 10 | rem) ^ 0x5412; // uint15
520 assert(bits >> 15 == 0);
521
522 // Draw first copy
523 for (int i = 0; i <= 5; i++)
524 setModule(qrcode, 8, i, getBit(bits, i));
525 setModule(qrcode, 8, 7, getBit(bits, 6));
526 setModule(qrcode, 8, 8, getBit(bits, 7));
527 setModule(qrcode, 7, 8, getBit(bits, 8));
528 for (int i = 9; i < 15; i++)
529 setModule(qrcode, 14 - i, 8, getBit(bits, i));
530
531 // Draw second copy
532 int qrsize = qrcodegen_getSize(qrcode);
533 for (int i = 0; i < 8; i++)
534 setModule(qrcode, qrsize - 1 - i, 8, getBit(bits, i));
535 for (int i = 8; i < 15; i++)
536 setModule(qrcode, 8, qrsize - 15 + i, getBit(bits, i));
537 setModule(qrcode, 8, qrsize - 8, true); // Always black
538 }
539
540
541 // Calculates and stores an ascending list of positions of alignment patterns
542 // for this version number, returning the length of the list (in the range [0,7]).
543 // Each position is in the range [0,177), and are used on both the x and y axes.
544 // This could be implemented as lookup table of 40 variable-length lists of unsigned bytes.
getAlignmentPatternPositions(int version,uint8_t result[7])545 testable int getAlignmentPatternPositions(int version, uint8_t result[7]) {
546 if (version == 1)
547 return 0;
548 int numAlign = version / 7 + 2;
549 int step = (version == 32) ? 26 :
550 (version*4 + numAlign*2 + 1) / (numAlign*2 - 2) * 2;
551 for (int i = numAlign - 1, pos = version * 4 + 10; i >= 1; i--, pos -= step)
552 result[i] = pos;
553 result[0] = 6;
554 return numAlign;
555 }
556
557
558 // Sets every pixel in the range [left : left + width] * [top : top + height] to black.
fillRectangle(int left,int top,int width,int height,uint8_t qrcode[])559 static void fillRectangle(int left, int top, int width, int height, uint8_t qrcode[]) {
560 for (int dy = 0; dy < height; dy++) {
561 for (int dx = 0; dx < width; dx++)
562 setModule(qrcode, left + dx, top + dy, true);
563 }
564 }
565
566
567
568 /*---- Drawing data modules and masking ----*/
569
570 // Draws the raw codewords (including data and ECC) onto the given QR Code. This requires the initial state of
571 // the QR Code to be black at function modules and white at codeword modules (including unused remainder bits).
drawCodewords(const uint8_t data[],int dataLen,uint8_t qrcode[])572 static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[]) {
573 int qrsize = qrcodegen_getSize(qrcode);
574 int i = 0; // Bit index into the data
575 // Do the funny zigzag scan
576 for (int right = qrsize - 1; right >= 1; right -= 2) { // Index of right column in each column pair
577 if (right == 6)
578 right = 5;
579 for (int vert = 0; vert < qrsize; vert++) { // Vertical counter
580 for (int j = 0; j < 2; j++) {
581 int x = right - j; // Actual x coordinate
582 bool upward = ((right + 1) & 2) == 0;
583 int y = upward ? qrsize - 1 - vert : vert; // Actual y coordinate
584 if (!getModule(qrcode, x, y) && i < dataLen * 8) {
585 bool black = getBit(data[i >> 3], 7 - (i & 7));
586 setModule(qrcode, x, y, black);
587 i++;
588 }
589 // If this QR Code has any remainder bits (0 to 7), they were assigned as
590 // 0/false/white by the constructor and are left unchanged by this method
591 }
592 }
593 }
594 assert(i == dataLen * 8);
595 }
596
597
598 // XORs the codeword modules in this QR Code with the given mask pattern.
599 // The function modules must be marked and the codeword bits must be drawn
600 // before masking. Due to the arithmetic of XOR, calling applyMask() with
601 // the same mask value a second time will undo the mask. A final well-formed
602 // QR Code needs exactly one (not zero, two, etc.) mask applied.
applyMask(const uint8_t functionModules[],uint8_t qrcode[],enum qrcodegen_Mask mask)603 static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], enum qrcodegen_Mask mask) {
604 assert(0 <= (int)mask && (int)mask <= 7); // Disallows qrcodegen_Mask_AUTO
605 int qrsize = qrcodegen_getSize(qrcode);
606 for (int y = 0; y < qrsize; y++) {
607 for (int x = 0; x < qrsize; x++) {
608 if (getModule(functionModules, x, y))
609 continue;
610 bool invert;
611 switch ((int)mask) {
612 case 0: invert = (x + y) % 2 == 0; break;
613 case 1: invert = y % 2 == 0; break;
614 case 2: invert = x % 3 == 0; break;
615 case 3: invert = (x + y) % 3 == 0; break;
616 case 4: invert = (x / 3 + y / 2) % 2 == 0; break;
617 case 5: invert = x * y % 2 + x * y % 3 == 0; break;
618 case 6: invert = (x * y % 2 + x * y % 3) % 2 == 0; break;
619 case 7: invert = ((x + y) % 2 + x * y % 3) % 2 == 0; break;
620 default: assert(false); return;
621 }
622 bool val = getModule(qrcode, x, y);
623 setModule(qrcode, x, y, val ^ invert);
624 }
625 }
626 }
627
628
629 // Calculates and returns the penalty score based on state of the given QR Code's current modules.
630 // This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
getPenaltyScore(const uint8_t qrcode[])631 static long getPenaltyScore(const uint8_t qrcode[]) {
632 int qrsize = qrcodegen_getSize(qrcode);
633 long result = 0;
634
635 // Adjacent modules in row having same color, and finder-like patterns
636 for (int y = 0; y < qrsize; y++) {
637 unsigned char runHistory[7] = {0};
638 bool color = false;
639 unsigned char runX = 0;
640 for (int x = 0; x < qrsize; x++) {
641 if (getModule(qrcode, x, y) == color) {
642 runX++;
643 if (runX == 5)
644 result += PENALTY_N1;
645 else if (runX > 5)
646 result++;
647 } else {
648 addRunToHistory(runX, runHistory);
649 if (!color && hasFinderLikePattern(runHistory))
650 result += PENALTY_N3;
651 color = getModule(qrcode, x, y);
652 runX = 1;
653 }
654 }
655 addRunToHistory(runX, runHistory);
656 if (color)
657 addRunToHistory(0, runHistory); // Dummy run of white
658 if (hasFinderLikePattern(runHistory))
659 result += PENALTY_N3;
660 }
661 // Adjacent modules in column having same color, and finder-like patterns
662 for (int x = 0; x < qrsize; x++) {
663 unsigned char runHistory[7] = {0};
664 bool color = false;
665 unsigned char runY = 0;
666 for (int y = 0; y < qrsize; y++) {
667 if (getModule(qrcode, x, y) == color) {
668 runY++;
669 if (runY == 5)
670 result += PENALTY_N1;
671 else if (runY > 5)
672 result++;
673 } else {
674 addRunToHistory(runY, runHistory);
675 if (!color && hasFinderLikePattern(runHistory))
676 result += PENALTY_N3;
677 color = getModule(qrcode, x, y);
678 runY = 1;
679 }
680 }
681 addRunToHistory(runY, runHistory);
682 if (color)
683 addRunToHistory(0, runHistory); // Dummy run of white
684 if (hasFinderLikePattern(runHistory))
685 result += PENALTY_N3;
686 }
687
688 // 2*2 blocks of modules having same color
689 for (int y = 0; y < qrsize - 1; y++) {
690 for (int x = 0; x < qrsize - 1; x++) {
691 bool color = getModule(qrcode, x, y);
692 if ( color == getModule(qrcode, x + 1, y) &&
693 color == getModule(qrcode, x, y + 1) &&
694 color == getModule(qrcode, x + 1, y + 1))
695 result += PENALTY_N2;
696 }
697 }
698
699 // Balance of black and white modules
700 int black = 0;
701 for (int y = 0; y < qrsize; y++) {
702 for (int x = 0; x < qrsize; x++) {
703 if (getModule(qrcode, x, y))
704 black++;
705 }
706 }
707 int total = qrsize * qrsize; // Note that size is odd, so black/total != 1/2
708 // Compute the smallest integer k >= 0 such that (45-5k)% <= black/total <= (55+5k)%
709 int k = (int)((labs(black * 20L - total * 10L) + total - 1) / total) - 1;
710 result += k * PENALTY_N4;
711 return result;
712 }
713
714
715 // Inserts the given value to the front of the given array, which shifts over the
716 // existing values and deletes the last value. A helper function for getPenaltyScore().
addRunToHistory(unsigned char run,unsigned char history[7])717 static void addRunToHistory(unsigned char run, unsigned char history[7]) {
718 memmove(&history[1], &history[0], 6 * sizeof(history[0]));
719 history[0] = run;
720 }
721
722
723 // Tests whether the given run history has the pattern of ratio 1:1:3:1:1 in the middle, and
724 // surrounded by at least 4 on either or both ends. A helper function for getPenaltyScore().
725 // Must only be called immediately after a run of white modules has ended.
hasFinderLikePattern(const unsigned char runHistory[7])726 static bool hasFinderLikePattern(const unsigned char runHistory[7]) {
727 unsigned char n = runHistory[1];
728 // The maximum QR Code size is 177, hence the run length n <= 177.
729 // Arithmetic is promoted to int, so n*4 will not overflow.
730 return n > 0 && runHistory[2] == n && runHistory[4] == n && runHistory[5] == n
731 && runHistory[3] == n * 3 && (runHistory[0] >= n * 4 || runHistory[6] >= n * 4);
732 }
733
734
735
736 /*---- Basic QR Code information ----*/
737
738 // Public function - see documentation comment in header file.
qrcodegen_getSize(const uint8_t qrcode[])739 int qrcodegen_getSize(const uint8_t qrcode[]) {
740 assert(qrcode != NULL);
741 int result = qrcode[0];
742 assert((qrcodegen_VERSION_MIN * 4 + 17) <= result
743 && result <= (qrcodegen_VERSION_MAX * 4 + 17));
744 return result;
745 }
746
747
748 // Public function - see documentation comment in header file.
qrcodegen_getModule(const uint8_t qrcode[],int x,int y)749 bool qrcodegen_getModule(const uint8_t qrcode[], int x, int y) {
750 assert(qrcode != NULL);
751 int qrsize = qrcode[0];
752 return (0 <= x && x < qrsize && 0 <= y && y < qrsize) && getModule(qrcode, x, y);
753 }
754
755
756 // Gets the module at the given coordinates, which must be in bounds.
getModule(const uint8_t qrcode[],int x,int y)757 testable bool getModule(const uint8_t qrcode[], int x, int y) {
758 int qrsize = qrcode[0];
759 assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
760 int index = y * qrsize + x;
761 return getBit(qrcode[(index >> 3) + 1], index & 7);
762 }
763
764
765 // Sets the module at the given coordinates, which must be in bounds.
setModule(uint8_t qrcode[],int x,int y,bool isBlack)766 testable void setModule(uint8_t qrcode[], int x, int y, bool isBlack) {
767 int qrsize = qrcode[0];
768 assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
769 int index = y * qrsize + x;
770 int bitIndex = index & 7;
771 int byteIndex = (index >> 3) + 1;
772 if (isBlack)
773 qrcode[byteIndex] |= 1 << bitIndex;
774 else
775 qrcode[byteIndex] &= (1 << bitIndex) ^ 0xFF;
776 }
777
778
779 // Sets the module at the given coordinates, doing nothing if out of bounds.
setModuleBounded(uint8_t qrcode[],int x,int y,bool isBlack)780 testable void setModuleBounded(uint8_t qrcode[], int x, int y, bool isBlack) {
781 int qrsize = qrcode[0];
782 if (0 <= x && x < qrsize && 0 <= y && y < qrsize)
783 setModule(qrcode, x, y, isBlack);
784 }
785
786
787 // Returns true iff the i'th bit of x is set to 1. Requires x >= 0 and 0 <= i <= 14.
getBit(int x,int i)788 static bool getBit(int x, int i) {
789 return ((x >> i) & 1) != 0;
790 }
791
792
793
794 /*---- Segment handling ----*/
795
796 // Public function - see documentation comment in header file.
qrcodegen_isAlphanumeric(const char * text)797 bool qrcodegen_isAlphanumeric(const char *text) {
798 assert(text != NULL);
799 for (; *text != '\0'; text++) {
800 if (strchr(ALPHANUMERIC_CHARSET, *text) == NULL)
801 return false;
802 }
803 return true;
804 }
805
806
807 // Public function - see documentation comment in header file.
qrcodegen_isNumeric(const char * text)808 bool qrcodegen_isNumeric(const char *text) {
809 assert(text != NULL);
810 for (; *text != '\0'; text++) {
811 if (*text < '0' || *text > '9')
812 return false;
813 }
814 return true;
815 }
816
817
818 // Public function - see documentation comment in header file.
qrcodegen_calcSegmentBufferSize(enum qrcodegen_Mode mode,size_t numChars)819 size_t qrcodegen_calcSegmentBufferSize(enum qrcodegen_Mode mode, size_t numChars) {
820 int temp = calcSegmentBitLength(mode, numChars);
821 if (temp == -1)
822 return SIZE_MAX;
823 assert(0 <= temp && temp <= INT16_MAX);
824 return ((size_t)temp + 7) / 8;
825 }
826
827
828 // Returns the number of data bits needed to represent a segment
829 // containing the given number of characters using the given mode. Notes:
830 // - Returns -1 on failure, i.e. numChars > INT16_MAX or
831 // the number of needed bits exceeds INT16_MAX (i.e. 32767).
832 // - Otherwise, all valid results are in the range [0, INT16_MAX].
833 // - For byte mode, numChars measures the number of bytes, not Unicode code points.
834 // - For ECI mode, numChars must be 0, and the worst-case number of bits is returned.
835 // An actual ECI segment can have shorter data. For non-ECI modes, the result is exact.
calcSegmentBitLength(enum qrcodegen_Mode mode,size_t numChars)836 testable int calcSegmentBitLength(enum qrcodegen_Mode mode, size_t numChars) {
837 // All calculations are designed to avoid overflow on all platforms
838 if (numChars > (unsigned int)INT16_MAX)
839 return -1;
840 long result = (long)numChars;
841 if (mode == qrcodegen_Mode_NUMERIC)
842 result = (result * 10 + 2) / 3; // ceil(10/3 * n)
843 else if (mode == qrcodegen_Mode_ALPHANUMERIC)
844 result = (result * 11 + 1) / 2; // ceil(11/2 * n)
845 else if (mode == qrcodegen_Mode_BYTE)
846 result *= 8;
847 else if (mode == qrcodegen_Mode_KANJI)
848 result *= 13;
849 else if (mode == qrcodegen_Mode_ECI && numChars == 0)
850 result = 3 * 8;
851 else { // Invalid argument
852 assert(false);
853 return -1;
854 }
855 assert(result >= 0);
856 if ((unsigned int)result > (unsigned int)INT16_MAX)
857 return -1;
858 return (int)result;
859 }
860
861
862 // Public function - see documentation comment in header file.
qrcodegen_makeBytes(const uint8_t data[],size_t len,uint8_t buf[])863 struct qrcodegen_Segment qrcodegen_makeBytes(const uint8_t data[], size_t len, uint8_t buf[]) {
864 assert(data != NULL || len == 0);
865 struct qrcodegen_Segment result;
866 result.mode = qrcodegen_Mode_BYTE;
867 result.bitLength = calcSegmentBitLength(result.mode, len);
868 assert(result.bitLength != -1);
869 result.numChars = (int)len;
870 if (len > 0)
871 memcpy(buf, data, len * sizeof(buf[0]));
872 result.data = buf;
873 return result;
874 }
875
876
877 // Public function - see documentation comment in header file.
qrcodegen_makeNumeric(const char * digits,uint8_t buf[])878 struct qrcodegen_Segment qrcodegen_makeNumeric(const char *digits, uint8_t buf[]) {
879 assert(digits != NULL);
880 struct qrcodegen_Segment result;
881 size_t len = strlen(digits);
882 result.mode = qrcodegen_Mode_NUMERIC;
883 int bitLen = calcSegmentBitLength(result.mode, len);
884 assert(bitLen != -1);
885 result.numChars = (int)len;
886 if (bitLen > 0)
887 memset(buf, 0, ((size_t)bitLen + 7) / 8 * sizeof(buf[0]));
888 result.bitLength = 0;
889
890 unsigned int accumData = 0;
891 int accumCount = 0;
892 for (; *digits != '\0'; digits++) {
893 char c = *digits;
894 assert('0' <= c && c <= '9');
895 accumData = accumData * 10 + (unsigned int)(c - '0');
896 accumCount++;
897 if (accumCount == 3) {
898 appendBitsToBuffer(accumData, 10, buf, &result.bitLength);
899 accumData = 0;
900 accumCount = 0;
901 }
902 }
903 if (accumCount > 0) // 1 or 2 digits remaining
904 appendBitsToBuffer(accumData, accumCount * 3 + 1, buf, &result.bitLength);
905 assert(result.bitLength == bitLen);
906 result.data = buf;
907 return result;
908 }
909
910
911 // Public function - see documentation comment in header file.
qrcodegen_makeAlphanumeric(const char * text,uint8_t buf[])912 struct qrcodegen_Segment qrcodegen_makeAlphanumeric(const char *text, uint8_t buf[]) {
913 assert(text != NULL);
914 struct qrcodegen_Segment result;
915 size_t len = strlen(text);
916 result.mode = qrcodegen_Mode_ALPHANUMERIC;
917 int bitLen = calcSegmentBitLength(result.mode, len);
918 assert(bitLen != -1);
919 result.numChars = (int)len;
920 if (bitLen > 0)
921 memset(buf, 0, ((size_t)bitLen + 7) / 8 * sizeof(buf[0]));
922 result.bitLength = 0;
923
924 unsigned int accumData = 0;
925 int accumCount = 0;
926 for (; *text != '\0'; text++) {
927 const char *temp = strchr(ALPHANUMERIC_CHARSET, *text);
928 assert(temp != NULL);
929 accumData = accumData * 45 + (unsigned int)(temp - ALPHANUMERIC_CHARSET);
930 accumCount++;
931 if (accumCount == 2) {
932 appendBitsToBuffer(accumData, 11, buf, &result.bitLength);
933 accumData = 0;
934 accumCount = 0;
935 }
936 }
937 if (accumCount > 0) // 1 character remaining
938 appendBitsToBuffer(accumData, 6, buf, &result.bitLength);
939 assert(result.bitLength == bitLen);
940 result.data = buf;
941 return result;
942 }
943
944
945 // Public function - see documentation comment in header file.
qrcodegen_makeEci(long assignVal,uint8_t buf[])946 struct qrcodegen_Segment qrcodegen_makeEci(long assignVal, uint8_t buf[]) {
947 struct qrcodegen_Segment result;
948 result.mode = qrcodegen_Mode_ECI;
949 result.numChars = 0;
950 result.bitLength = 0;
951 if (assignVal < 0) {
952 assert(false);
953 } else if (assignVal < (1 << 7)) {
954 memset(buf, 0, 1 * sizeof(buf[0]));
955 appendBitsToBuffer(assignVal, 8, buf, &result.bitLength);
956 } else if (assignVal < (1 << 14)) {
957 memset(buf, 0, 2 * sizeof(buf[0]));
958 appendBitsToBuffer(2, 2, buf, &result.bitLength);
959 appendBitsToBuffer(assignVal, 14, buf, &result.bitLength);
960 } else if (assignVal < 1000000L) {
961 memset(buf, 0, 3 * sizeof(buf[0]));
962 appendBitsToBuffer(6, 3, buf, &result.bitLength);
963 appendBitsToBuffer(assignVal >> 10, 11, buf, &result.bitLength);
964 appendBitsToBuffer(assignVal & 0x3FF, 10, buf, &result.bitLength);
965 } else {
966 assert(false);
967 }
968 result.data = buf;
969 return result;
970 }
971
972
973 // Calculates the number of bits needed to encode the given segments at the given version.
974 // Returns a non-negative number if successful. Otherwise returns -1 if a segment has too
975 // many characters to fit its length field, or the total bits exceeds INT16_MAX.
getTotalBits(const struct qrcodegen_Segment segs[],size_t len,int version)976 testable int getTotalBits(const struct qrcodegen_Segment segs[], size_t len, int version) {
977 assert(segs != NULL || len == 0);
978 long result = 0;
979 for (size_t i = 0; i < len; i++) {
980 int numChars = segs[i].numChars;
981 int bitLength = segs[i].bitLength;
982 assert(0 <= numChars && numChars <= INT16_MAX);
983 assert(0 <= bitLength && bitLength <= INT16_MAX);
984 int ccbits = numCharCountBits(segs[i].mode, version);
985 assert(0 <= ccbits && ccbits <= 16);
986 if (numChars >= (1L << ccbits))
987 return -1; // The segment's length doesn't fit the field's bit width
988 result += 4L + ccbits + bitLength;
989 if (result > INT16_MAX)
990 return -1; // The sum might overflow an int type
991 }
992 assert(0 <= result && result <= INT16_MAX);
993 return (int)result;
994 }
995
996
997 // Returns the bit width of the character count field for a segment in the given mode
998 // in a QR Code at the given version number. The result is in the range [0, 16].
numCharCountBits(enum qrcodegen_Mode mode,int version)999 static int numCharCountBits(enum qrcodegen_Mode mode, int version) {
1000 assert(qrcodegen_VERSION_MIN <= version && version <= qrcodegen_VERSION_MAX);
1001 int i = (version + 7) / 17;
1002 switch (mode) {
1003 case qrcodegen_Mode_NUMERIC : { static const int temp[] = {10, 12, 14}; return temp[i]; }
1004 case qrcodegen_Mode_ALPHANUMERIC: { static const int temp[] = { 9, 11, 13}; return temp[i]; }
1005 case qrcodegen_Mode_BYTE : { static const int temp[] = { 8, 16, 16}; return temp[i]; }
1006 case qrcodegen_Mode_KANJI : { static const int temp[] = { 8, 10, 12}; return temp[i]; }
1007 case qrcodegen_Mode_ECI : return 0;
1008 default: assert(false); return -1; // Dummy value
1009 }
1010 }
1011
qrcodegen_getMinFitVersion(enum qrcodegen_Ecc ecl,size_t dataLen)1012 int qrcodegen_getMinFitVersion(enum qrcodegen_Ecc ecl, size_t dataLen)
1013 {
1014 struct qrcodegen_Segment seg;
1015 seg.mode = qrcodegen_Mode_BYTE;
1016 seg.bitLength = calcSegmentBitLength(seg.mode, dataLen);
1017 seg.numChars = (int)dataLen;
1018
1019 for (int version = qrcodegen_VERSION_MIN; version <= qrcodegen_VERSION_MAX; version++) {
1020 int dataCapacityBits = getNumDataCodewords(version, ecl) * 8; // Number of data bits available
1021 int dataUsedBits = getTotalBits(&seg, 1, version);
1022 if (dataUsedBits != -1 && dataUsedBits <= dataCapacityBits)
1023 return version;
1024 }
1025 return -1;
1026 }
1027
qrcodegen_version2size(int version)1028 int qrcodegen_version2size(int version)
1029 {
1030 if (version < qrcodegen_VERSION_MIN || version > qrcodegen_VERSION_MAX) {
1031 return -1;
1032 }
1033
1034 return ((version - 1)*4 + 21);
1035 }
1036
