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/*
* 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 <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();
}
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