mirror of https://github.com/aria2/aria2
SimpleRandmizer: Fix certain bits generated by getRandomBytes are always 0
This is because in Linux RAND_MAX is 2**31-1 and we used int32_t to hold random number from random() and got each bytes. This means that highest bit is always unset. In little endian system, every 4n-th (n >=0) byte has highest bit is unset. To fix this, we just use lower 2 bytes of random().pull/135/merge
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ac996737e5
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7f18494a8c
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@ -123,11 +123,12 @@ void SimpleRandomizer::getRandomBytes(unsigned char *buf, size_t len)
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}
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#else
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while (len) {
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// If RAND_MAX is less than 2**16-1, we are in trouble.
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union {
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int32_t r;
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uint8_t b[4];
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} r = { (int32_t)random() };
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for (auto i = 0; i < 4 && len; ++i, --len) {
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uint16_t r;
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uint8_t b[2];
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} r = { (uint16_t)(random() & 0xffffu) };
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for (auto i = 0; i < 2 && len; ++i, --len) {
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*buf++ = r.b[i];
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}
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}
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