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/*
* 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 "config.h"
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <fcntl.h>
#include <math.h>
#include <time.h>
#include <string.h>
#include "avassert.h"
#include "timer.h"
#include "random_seed.h"
#include "sha.h"
#include "intreadwrite.h"
#ifndef TEST
#define TEST 0
#endif
static int read_random(uint32_t *dst, const char *file)
{
#if HAVE_UNISTD_H
int fd = open(file, O_RDONLY);
int err = -1;
if (fd == -1)
return -1;
err = read(fd, dst, sizeof(*dst));
close(fd);
return err;
#else
return -1;
#endif
}
static uint32_t get_generic_seed(void)
{
uint8_t tmp[120];
struct AVSHA *sha = (void*)tmp;
clock_t last_t = 0;
static uint64_t i = 0;
static uint32_t buffer[512] = {0};
unsigned char digest[20];
uint64_t last_i = i;
av_assert0(sizeof(tmp) >= av_sha_size);
if(TEST){
memset(buffer, 0, sizeof(buffer));
last_i = i = 0;
}else{
#ifdef AV_READ_TIME
buffer[13] ^= AV_READ_TIME();
buffer[41] ^= AV_READ_TIME()>>32;
#endif
}
for (;;) {
clock_t t = clock();
if(last_t == t){
buffer[i&511]++;
}else{
buffer[++i&511]+= (t-last_t) % 3294638521U;
if(last_i && i-last_i > 4 || i-last_i > 64 || TEST && i-last_i > 8)
break;
}
last_t = t;
}
if(TEST)
buffer[0] = buffer[1] = 0;
av_sha_init(sha, 160);
av_sha_update(sha, (uint8_t*)buffer, sizeof(buffer));
av_sha_final(sha, digest);
return AV_RB32(digest) + AV_RB32(digest+16);
}
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 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
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