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avutil/random_seed: Improve get_generic_seed() with higher precission clock()

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Tested-by: Thomas Turner <thomastdt@googlemail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit da73d95bad4736c5e0a6b4b1a811f4dd4525bb4c)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2016-12-22 03:59:03 +01:00
parent 1825f7670a
commit 02073b5ab1
1 changed files with 6 additions and 4 deletions
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10
libavutil/random_seed.c
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@ -67,6 +67,7 @@ static uint32_t get_generic_seed(void)
uint8_t tmp[120];
struct AVSHA *sha = (void*)tmp;
clock_t last_t = 0;
clock_t last_td = 0;
static uint64_t i = 0;
static uint32_t buffer[512] = { 0 };
unsigned char digest[20];
@ -86,11 +87,12 @@ static uint32_t get_generic_seed(void)
for (;;) {
clock_t t = clock();
if (last_t == t) {
buffer[i & 511]++;
if (last_t + 2*last_td + 1 >= t) {
last_td = t - last_t;
buffer[i & 511] = 1664525*buffer[i & 511] + 1013904223 + (last_td % 3294638521U);
} else {
buffer[++i & 511] += (t - last_t) % 3294638521U;
last_td = t - last_t;
buffer[++i & 511] += last_td % 3294638521U;
if (last_i && i - last_i > 4 || i - last_i > 64 || TEST && i - last_i > 8)
break;
}