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QR-Code-generator
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Updated and added numerous comments in C code.

This commit is contained in:
Project Nayuki 2017-04-20 06:39:03 +00:00
parent c91d29dcee
commit 9a100aed7d
2 changed files with 36 additions and 15 deletions
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48
c/qrcodegen.c
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@ -31,6 +31,12 @@
/*---- Forward declarations for private functions ----*/
// Note: All public and private functions defined in this source file are "pure", in the sense that
// they take input data only from arguments, return output data or store in pointer arguments,
// perform no I/O (e.g. reading clock or writing to console), and don't read/write global variables.
// Also, each of these functions allocate only a small constant amount of memory on the stack,
// they don't allocate or free anything on the heap, and they are thread-safe.
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);
@ -99,8 +105,8 @@ int qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[
int textLen = 0;
bool isNumeric = true;
bool isAlphanumeric = true;
for (const char *p = text; *p != '\0'; p++, textLen++) {
if (textLen == INT16_MAX) // Note: INT16_MAX < INT_MAX && INT16_MAX < SIZE_MAX
for (const char *p = text; *p != '\0'; p++, textLen++) { // Read every character
if (textLen == INT16_MAX) // Note: INT16_MAX <= INT_MAX && INT16_MAX <= SIZE_MAX
return 0;
char c = *p;
if (c < '0' || c > '9') {
@ -128,12 +134,15 @@ int qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[
(isNumeric ? 10 : 9), (isNumeric ? 12 : 11), (isNumeric ? 14 : 13));
if (version == 0)
return 0;
// Make header of bit sequence
memset(qrcode, 0, qrcodegen_BUFFER_LEN_FOR_VERSION(version) * sizeof(qrcode[0]));
int bitLen = 0;
appendBitsToBuffer((isNumeric ? 1 : 2), 4, qrcode, &bitLen);
int lengthBits = (version <= 9 ? 9 : (version <= 26 ? 11 : 13)) + (isNumeric ? 1 : 0);
appendBitsToBuffer((unsigned int)textLen, lengthBits, qrcode, &bitLen);
// Append data segment bits
if (isNumeric) {
int accumData = 0;
int accumCount = 0;
@ -164,6 +173,7 @@ int qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[
appendBitsToBuffer(accumData, 6, qrcode, &bitLen);
}
// Make QR Code
encodeQrCodeTail(qrcode, bitLen, tempBuffer, version, ecl, mask, boostEcl);
return version;
}
@ -175,13 +185,15 @@ int qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcode
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 <= 65535 <= INT_MAX
// 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);
@ -221,9 +233,11 @@ static int fitVersionToData(int minVersion, int maxVersion, enum qrcodegen_Ecc e
}
// Given data codewords in dataAndQrcode already padded to the length specified by the
// version and ECC level, this function adds ECC bytes, interleaves blocks, renders the
// QR Code symbol back to the array dataAndQrcode, and handles automatic mask selection.
// Given a data bit sequence in dataAndQrcode without terminator or padding or ECC, plus the given QR Code
// encoding parameters, this function handles ECC level boosting, bit stream termination and padding,
// ECC computation, and block interleaving. Then the function renders the QR Code symbol back to the array
// dataAndQrcode and handles automatic mask selection. The initial bit length must fit the given version and
// ECC level, and each of the two arrays must have length at least qrcodegen_BUFFER_LEN_FOR_VERSION(version).
static void encodeQrCodeTail(uint8_t dataAndQrcode[], int bitLen, uint8_t tempBuffer[],
int version, enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, bool boostEcl) {
@ -234,6 +248,7 @@ static void encodeQrCodeTail(uint8_t dataAndQrcode[], int bitLen, uint8_t tempBu
}
int dataCapacityBits = getNumDataCodewords(version, ecl) * 8;
// Add terminator, bit padding, byte padding
int terminatorBits = dataCapacityBits - bitLen;
if (terminatorBits > 4)
terminatorBits = 4;
@ -243,12 +258,15 @@ static void encodeQrCodeTail(uint8_t dataAndQrcode[], int bitLen, uint8_t tempBu
appendBitsToBuffer(padByte, 8, dataAndQrcode, &bitLen);
assert(bitLen % 8 == 0);
// Draw function and data codeword modules
int qrsize = qrcodegen_getSize(version);
appendErrorCorrection(dataAndQrcode, version, ecl, tempBuffer);
initializeFunctionModules(version, dataAndQrcode);
drawCodewords(tempBuffer, getNumRawDataModules(version) / 8, dataAndQrcode, qrsize);
drawWhiteFunctionModules(dataAndQrcode, version);
initializeFunctionModules(version, tempBuffer);
// Handle masking
if (mask == qrcodegen_Mask_AUTO) { // Automatically choose best mask
long minPenalty = LONG_MAX;
for (int i = 0; i < 8; i++) {
@ -416,8 +434,8 @@ static void setModuleBounded(uint8_t qrcode[], int qrsize, int x, int y, bool is
/*---- QR Code drawing functions ----*/
// Fills the given QR Code grid with white modules for the given version's size,
// then marks every function module in the QR Code as black.
// Clears the given QR Code grid with white modules for the given
// version's size, then marks every function module as black.
static void initializeFunctionModules(int version, uint8_t qrcode[]) {
// Initialize QR Code
int qrsize = qrcodegen_getSize(version);
@ -444,7 +462,7 @@ static void initializeFunctionModules(int version, uint8_t qrcode[]) {
}
}
// Fill version
// Fill version blocks
if (version >= 7) {
fillRectangle(qrsize - 11, 0, 3, 6, qrcode, qrsize);
fillRectangle(0, qrsize - 11, 6, 3, qrcode, qrsize);
@ -463,7 +481,7 @@ static void drawWhiteFunctionModules(uint8_t qrcode[], int version) {
setModule(qrcode, qrsize, i, 6, false);
}
// Draw 3 finder patterns
// Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules)
for (int i = -4; i <= 4; i++) {
for (int j = -4; j <= 4; j++) {
int dist = abs(i);
@ -493,7 +511,7 @@ static void drawWhiteFunctionModules(uint8_t qrcode[], int version) {
}
}
// Draw version block
// Draw version blocks
if (version >= 7) {
// Calculate error correction code and pack bits
int rem = version; // version is uint6, in the range [7, 40]
@ -515,8 +533,9 @@ static void drawWhiteFunctionModules(uint8_t qrcode[], int version) {
}
// Based on the given ECC level and mask, this calculates the format bits
// and draws their black and white modules onto the given QR Code.
// 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 drawWhiteFunctionModules() which might skip black modules.
static void drawFormatBits(enum qrcodegen_Ecc ecl, enum qrcodegen_Mask mask, uint8_t qrcode[], int qrsize) {
// Calculate error correction code and pack bits
assert(0 <= (int)mask && (int)mask <= 7);
@ -626,7 +645,8 @@ static void appendErrorCorrection(uint8_t data[], int version, enum qrcodegen_Ec
// 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 may not be a multiple of 8.
// 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;

3
c/qrcodegen.h
View File

@ -81,7 +81,8 @@ enum qrcodegen_Mask {
* Encodes the given text data to a QR Code symbol, returning the actual version number used.
* If the data is too long to fit in any version in the given range at the given ECC level,
* then 0 is returned. Both dataAndTemp and qrcode each must have length at least
* qrcodegen_BUFFER_LEN_FOR_VERSION(maxVersion).
* qrcodegen_BUFFER_LEN_FOR_VERSION(maxVersion). The text must be encoded in UTF-8.
* The resulting QR Code may use numeric, alphanumeric, or byte mode to encode the text.
*/
int 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);