mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-07 11:13:41 +02:00
946de27d25
Reviewed-by: Nicolas George <nicolas.george@normalesup.org> Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
109 lines
2.5 KiB
C
109 lines
2.5 KiB
C
/*
|
|
* Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
|
|
*
|
|
* This file is part of FFmpeg.
|
|
*
|
|
* FFmpeg is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* FFmpeg is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with FFmpeg; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
#include <unistd.h>
|
|
#include <fcntl.h>
|
|
#include <math.h>
|
|
#include <time.h>
|
|
#include "timer.h"
|
|
#include "random_seed.h"
|
|
|
|
static int read_random(uint32_t *dst, const char *file)
|
|
{
|
|
int fd = open(file, O_RDONLY);
|
|
int err = -1;
|
|
|
|
if (fd == -1)
|
|
return -1;
|
|
err = read(fd, dst, sizeof(*dst));
|
|
close(fd);
|
|
|
|
return err;
|
|
}
|
|
|
|
static uint32_t get_generic_seed(void)
|
|
{
|
|
clock_t last_t = 0;
|
|
int bits = 0;
|
|
uint64_t random = 0;
|
|
unsigned i;
|
|
float s = 0.000000000001;
|
|
|
|
for (i = 0; bits < 64; i++) {
|
|
clock_t t = clock();
|
|
if (last_t && fabs(t - last_t) > s || t == (clock_t) -1) {
|
|
if (i < 10000 && s < (1 << 24)) {
|
|
s += s;
|
|
i = t = 0;
|
|
} else {
|
|
random = 2 * random + (i & 1);
|
|
bits++;
|
|
}
|
|
}
|
|
last_t = t;
|
|
}
|
|
#ifdef AV_READ_TIME
|
|
random ^= AV_READ_TIME();
|
|
#else
|
|
random ^= clock();
|
|
#endif
|
|
|
|
random += random >> 32;
|
|
|
|
return random;
|
|
}
|
|
|
|
uint32_t av_get_random_seed(void)
|
|
{
|
|
uint32_t seed;
|
|
|
|
if (read_random(&seed, "/dev/urandom") == sizeof(seed))
|
|
return seed;
|
|
if (read_random(&seed, "/dev/random") == sizeof(seed))
|
|
return seed;
|
|
return get_generic_seed();
|
|
}
|
|
|
|
#ifdef TEST
|
|
#undef printf
|
|
#define N 256
|
|
#include <stdio.h>
|
|
|
|
int main(void)
|
|
{
|
|
int i, j, retry;
|
|
uint32_t seeds[N];
|
|
|
|
for (retry=0; retry<3; retry++){
|
|
for (i=0; i<N; i++){
|
|
seeds[i] = av_get_random_seed();
|
|
for (j=0; j<i; j++)
|
|
if (seeds[j] == seeds[i])
|
|
goto retry;
|
|
}
|
|
printf("seeds OK\n");
|
|
return 0;
|
|
retry:;
|
|
}
|
|
printf("FAIL at %d with %X\n", j, seeds[j]);
|
|
return 1;
|
|
}
|
|
#endif
|