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util/rand_xor: fallback Linux to time-based instead of fixed seed

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When the caller asked for a randomised_seed, we should fall back to the
time-based seed instead of the fixed seed.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/2316>
This commit is contained in:
Eric Engestrom 2019-10-13 16:09:22 +01:00 • committed by Marge Bot
parent e0ce684aae
commit d76abe98cf
1 changed files with 14 additions and 22 deletions
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36
src/util/rand_xor.c
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@ -28,10 +28,10 @@
#endif
#include <unistd.h>
#include <fcntl.h>
#else
#include <time.h>
#endif
#include <time.h>
#include "rand_xor.h"
/* Super fast random number generator.
@ -56,8 +56,12 @@ rand_xorshift128plus(uint64_t seed[2])
void
s_rand_xorshift128plus(uint64_t seed[2], bool randomised_seed)
{
if (!randomised_seed)
goto fixed_seed;
if (!randomised_seed) {
/* Use a fixed seed */
seed[0] = 0x3bffb83978e24f88;
seed[1] = 0x9238d5d56c71cd35;
return;
}
#if defined(__linux__)
size_t seed_size = sizeof(uint64_t) * 2;
@ -69,27 +73,15 @@ s_rand_xorshift128plus(uint64_t seed[2], bool randomised_seed)
#endif
int fd = open("/dev/urandom", O_RDONLY);
if (fd < 0)
goto fixed_seed;
if (read(fd, seed, seed_size) != seed_size) {
if (fd >= 0) {
if (read(fd, seed, seed_size) == seed_size) {
close(fd);
return;
}
close(fd);
goto fixed_seed;
}
close(fd);
return;
#else
seed[0] = 0x3bffb83978e24f88;
seed[1] = time(NULL);
return;
#endif
fixed_seed:
/* Fallback to a fixed seed */
seed[0] = 0x3bffb83978e24f88;
seed[1] = 0x9238d5d56c71cd35;
seed[1] = time(NULL);
}