| /* |
| * 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(); |
| } |
| |
| #ifdef TEST |
| #undef printf |
| #define N 256 |
| #include <stdio.h> |
| |
| int main(void) |
| { |
| int i, j, retry; |
| uint32_t seeds[N]; |
| |
| for (retry=0; retry<3; retry++){ |
| for (i=0; i<N; i++){ |
| seeds[i] = av_get_random_seed(); |
| for (j=0; j<i; j++) |
| if (seeds[j] == seeds[i]) |
| goto retry; |
| } |
| printf("seeds OK\n"); |
| return 0; |
| retry:; |
| } |
| printf("FAIL at %d with %X\n", j, seeds[j]); |
| return 1; |
| } |
| #endif |