/* * 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 "config.h" #if HAVE_UNISTD_H #include <unistd.h> #endif #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) { #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) { 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(); }