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Simplified the arithmetic of an internal C function.

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Project Nayuki
2018-09-18 08:58:30 +00:00
parent a19c7aa21b
commit aa264f5a4d
1 changed files with 17 additions and 37 deletions
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c/qrcodegen.c
+17 -37
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@@ -714,48 +714,28 @@ size_t qrcodegen_calcSegmentBufferSize(enum qrcodegen_Mode mode, size_t numChars
// - 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) {
const int LIMIT = INT16_MAX; // Can be configured as high as INT_MAX
if (numChars > (unsigned int)LIMIT)
// All calculations are designed to avoid overflow on all platforms
if (numChars > (unsigned int)INT16_MAX)
return -1;
int n = (int)numChars;
int result;
if (mode == qrcodegen_Mode_NUMERIC) {
// n * 3 + ceil(n / 3)
if (n > LIMIT / 3)
goto overflow;
result = n * 3;
int temp = n / 3 + (n % 3 > 0 ? 1 : 0);
if (temp > LIMIT - result)
goto overflow;
result += temp;
} else if (mode == qrcodegen_Mode_ALPHANUMERIC) {
// n * 5 + ceil(n / 2)
if (n > LIMIT / 5)
goto overflow;
result = n * 5;
int temp = n / 2 + n % 2;
if (temp > LIMIT - result)
goto overflow;
result += temp;
} else if (mode == qrcodegen_Mode_BYTE) {
if (n > LIMIT / 8)
goto overflow;
result = n * 8;
} else if (mode == qrcodegen_Mode_KANJI) {
if (n > LIMIT / 13)
goto overflow;
result = n * 13;
} else if (mode == qrcodegen_Mode_ECI && numChars == 0)
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 {
else { // Invalid argument
assert(false);
return -1;
}
assert(0 <= result && result <= LIMIT);
return result;
overflow:
return -1;
assert(result >= 0);
if (result > (unsigned int)INT16_MAX)
return -1;
return (int)result;
}