/* * 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 <unistd.h> #include <fcntl.h> #include "timer.h" #include "time.h" #include "random_seed.h" #include "avutil.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(); }