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QR-Code-generator
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Added C functions to do basic arithmetic with overflow checks, updated code to use these functions.

This commit is contained in:
Project Nayuki 2017-04-20 05:12:55 +00:00
parent 6229fa48cd
commit 481a1c0de3
1 changed files with 34 additions and 20 deletions
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54
c/qrcodegen.c
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@ -51,6 +51,9 @@ static int getNumRawDataModules(int version);
static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[], int qrsize);
static void applyMask(const uint8_t functionModules[], uint8_t qrcode[], int qrsize, int mask);
static int checkedAdd(int x, int y);
static int checkedMultiply(int x, int y);
static void calcReedSolomonGenerator(int degree, uint8_t result[]);
static void calcReedSolomonRemainder(const uint8_t data[], int dataLen, const uint8_t generator[], int degree, uint8_t result[]);
static uint8_t finiteFieldMultiply(uint8_t x, uint8_t y);
@ -110,19 +113,13 @@ int qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[
int textBits;
if (isNumeric) { // textBits = textLen * 3 + ceil(textLen / 3)
if (textLen > INT_MAX / 3)
textBits = checkedAdd(checkedMultiply(textLen, 3), checkedAdd(textLen, 2) / 3);
if (textBits < 0)
return 0;
textBits = textLen * 3;
if (textLen > INT_MAX - 2 || (textLen + 2) / 3 > INT_MAX - textBits)
return 0;
textBits += (textLen + 2) / 3;
} else if (isAlphanumeric) { // textBits = textLen * 5 + ceil(textLen / 2)
if (textLen > INT_MAX / 5)
textBits = checkedAdd(checkedMultiply(textLen, 5), checkedAdd(textLen, 1) / 2);
if (textBits < 0)
return 0;
textBits = textLen * 5;
if (textLen > INT_MAX - 1 || (textLen + 1) / 2 > INT_MAX - textBits)
return 0;
textBits += (textLen + 1) / 2;
} else { // Use binary mode
if (textLen > qrcodegen_BUFFER_LEN_FOR_VERSION(maxVersion))
return 0;
@ -144,11 +141,8 @@ int qrcodegen_encodeText(const char *text, uint8_t tempBuffer[], uint8_t qrcode[
lengthBits = isNumeric ? 14 : 13;
if (textLen < (1 << lengthBits)) {
dataCapacityBits = getNumDataCodewords(version, ecl) * 8; // Number of data bits available
dataUsedBits = 4 + lengthBits;
if (textBits > INT_MAX - dataUsedBits)
continue;
dataUsedBits += textBits;
if (dataUsedBits <= dataCapacityBits)
dataUsedBits = checkedAdd(4 + lengthBits, textBits);
if (0 <= dataUsedBits && 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
@ -199,6 +193,9 @@ int qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcode
enum qrcodegen_Ecc ecl, int minVersion, int maxVersion, enum qrcodegen_Mask mask, bool boostEcl) {
assert(qrcodegen_VERSION_MIN <= minVersion && minVersion <= maxVersion && maxVersion <= qrcodegen_VERSION_MAX);
assert(0 <= (int)ecl && (int)ecl <= 3 && -1 <= (int)mask && (int)mask <= 7);
if (dataLen > INT16_MAX)
return 0;
// Now dataLen <= INT_MAX, since int has at least 16 bits
int version;
int dataUsedBits = -1;
@ -206,11 +203,8 @@ int qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcode
for (version = minVersion; ; version++) {
if ((version <= 9 && dataLen < (1U << 8)) || dataLen < (1U << 16)) {
dataCapacityBits = getNumDataCodewords(version, ecl) * 8; // Number of data bits available
dataUsedBits = 4 + (version <= 9 ? 8 : 16);
if (dataLen > (unsigned int)INT_MAX / 8 || (unsigned int)(INT_MAX - dataUsedBits) < dataLen * 8)
continue;
dataUsedBits += dataLen * 8;
if (dataUsedBits <= dataCapacityBits)
dataUsedBits = checkedAdd(4 + (version <= 9 ? 8 : 16), checkedMultiply((int)dataLen, 8));
if (0 <= dataUsedBits && 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
@ -675,6 +669,26 @@ static void drawCodewords(const uint8_t data[], int dataLen, uint8_t qrcode[], i
}
// Tries to add the given non-negative integers, with strict overflow checking.
// Negative inputs or output indicate the computation would overflow.
static int checkedAdd(int x, int y) {
if (x < 0 || y < 0 || x > INT_MAX - y)
return -1;
else
return x + y;
}
// Tries to multiply the given non-negative integers, with strict overflow checking.
// Negative inputs or output indicate the computation would overflow.
static int checkedMultiply(int x, int y) {
if (x < 0 || y < 0 || x > INT_MAX / y)
return -1;
else
return x * y;
}
/*---- Reed-Solomon ECC generator functions ----*/