mirror of https://git.ffmpeg.org/ffmpeg.git
83 lines
2.0 KiB
C
83 lines
2.0 KiB
C
/*
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* Copyright (c) 2009 Baptiste Coudurier <baptiste.coudurier@gmail.com>
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <unistd.h>
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#include <fcntl.h>
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#include "timer.h"
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#include "time.h"
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#include "random_seed.h"
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#include "avutil.h"
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static int read_random(uint32_t *dst, const char *file)
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{
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int fd = open(file, O_RDONLY);
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int err = -1;
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if (fd == -1)
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return -1;
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err = read(fd, dst, sizeof(*dst));
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close(fd);
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return err;
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}
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static uint32_t get_generic_seed(void)
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{
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clock_t last_t=0;
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int bits=0;
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uint64_t random=0;
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unsigned i;
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float s=0.000000000001;
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for(i=0;bits<64;i++){
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clock_t t= clock();
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if(last_t && fabs(t-last_t)>s || t==(clock_t)-1){
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if(i<10000 && s<(1<<24)){
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s+=s;
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i=t=0;
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}else{
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random= 2*random + (i&1);
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bits++;
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}
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}
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last_t= t;
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}
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#ifdef AV_READ_TIME
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random ^= AV_READ_TIME();
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#else
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random ^= clock();
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#endif
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random += random>>32;
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return random;
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}
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uint32_t av_get_random_seed(void)
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{
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uint32_t seed;
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if (read_random(&seed, "/dev/urandom") == sizeof(seed))
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return seed;
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if (read_random(&seed, "/dev/random") == sizeof(seed))
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return seed;
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return get_generic_seed();
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}
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