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@@ -1575,25 +1575,32 @@ mg_snprintf(const struct mg_connection *conn,
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static int64_t
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get_random(void)
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{
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- static uint64_t lfsr = 0;
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- static uint64_t lcg = 0;
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+ static uint64_t lfsr = 0; /* Linear feedback shift register */
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+ static uint64_t lcg = 0; /* Linear congruential generator */
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struct timespec now;
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memset(&now, 0, sizeof(now));
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clock_gettime(CLOCK_MONOTONIC, &now);
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if (lfsr == 0) {
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- lfsr = (((uint64_t)now.tv_sec) << 21) ^ (uint64_t)now.tv_nsec
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- ^ (uint64_t)(ptrdiff_t)&now;
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+ /* lfsr will be only 0 if has not been initialized,
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+ * so this code is called only once. */
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+ lfsr = (((uint64_t)now.tv_sec) << 21) ^ ((uint64_t)now.tv_nsec)
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+ ^ ((uint64_t)(ptrdiff_t)&now) ^ ((uint64_t)pthread_self())
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+ ^ (((uint64_t)time(NULL)) << 33);
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lcg = (((uint64_t)now.tv_sec) << 25) + (uint64_t)now.tv_nsec
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+ (uint64_t)(ptrdiff_t)&now;
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} else {
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+ /* Get the next step of both random number generators. */
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lfsr = (lfsr >> 1)
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| ((((lfsr >> 0) ^ (lfsr >> 1) ^ (lfsr >> 3) ^ (lfsr >> 4)) & 1)
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<< 63);
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lcg = lcg * 6364136223846793005 + 1442695040888963407;
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}
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+ /* Combining two pseudo-random number generators and a high resolution part
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+ * of the current server time will make it hard (impossible?) to guess the
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+ * next number. */
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return (lfsr ^ lcg ^ now.tv_nsec);
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}
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bel2125