mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-12-22 15:23:11 +00:00
91 lines
2.2 KiB
C
91 lines
2.2 KiB
C
/*
|
|
* Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
|
|
*
|
|
* This file is part of Libav.
|
|
*
|
|
* Libav 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.
|
|
*
|
|
* Libav 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 Libav; 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 "timer.h"
|
|
#include "time.h"
|
|
#include "random_seed.h"
|
|
#include "avutil.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();
|
|
}
|
|
|
|
#if LIBAVUTIL_VERSION_MAJOR < 51
|
|
attribute_deprecated uint32_t ff_random_get_seed(void);
|
|
uint32_t ff_random_get_seed(void)
|
|
{
|
|
return av_get_random_seed();
|
|
}
|
|
#endif
|