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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 <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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