mirror of
https://github.com/FFmpeg/FFmpeg.git
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66531c75d3
The new code is faster and reuses the previous state in case of multiple calls. For testing the iterations are reduced and several entropy sources are disabled. Its based on SHA-1 Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
126 lines
2.9 KiB
C
126 lines
2.9 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 FFmpeg.
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*
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* FFmpeg 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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* FFmpeg 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 FFmpeg; 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 <math.h>
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#include <time.h>
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#include <string.h>
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#include "timer.h"
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#include "random_seed.h"
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#include "sha.h"
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#include "intreadwrite.h"
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#ifndef TEST
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#define TEST 0
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#endif
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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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uint8_t tmp[av_sha_size];
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struct AVSHA *sha = (void*)tmp;
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clock_t last_t = 0;
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static uint64_t i = 0;
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static uint32_t buffer[512] = {0};
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unsigned char digest[32];
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uint64_t last_i = i;
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if(TEST){
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memset(buffer, 0, sizeof(buffer));
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last_i = i = 0;
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}else{
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#ifdef AV_READ_TIME
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buffer[13] ^= AV_READ_TIME();
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buffer[41] ^= AV_READ_TIME()>>32;
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#endif
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}
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for (;;) {
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clock_t t = clock();
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if(last_t == t){
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buffer[i&511]++;
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}else{
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buffer[++i&511]+= (t-last_t) % 3294638521U;
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if(last_i && i-last_i > 4 || i-last_i > 64 || TEST && i-last_i > 8)
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break;
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}
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last_t = t;
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}
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if(TEST)
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buffer[0] = buffer[1] = 0;
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av_sha_init(sha, 160);
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av_sha_update(sha, (uint8_t*)buffer, sizeof(buffer));
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av_sha_final(sha, digest);
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return AV_RB32(digest) + AV_RB32(digest+32);
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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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#if TEST
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#undef printf
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#define N 256
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#include <stdio.h>
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int main(void)
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{
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int i, j, retry;
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uint32_t seeds[N];
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for (retry=0; retry<3; retry++){
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for (i=0; i<N; i++){
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seeds[i] = av_get_random_seed();
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for (j=0; j<i; j++)
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if (seeds[j] == seeds[i])
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goto retry;
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}
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printf("seeds OK\n");
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return 0;
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retry:;
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}
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printf("FAIL at %d with %X\n", j, seeds[j]);
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return 1;
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}
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#endif
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