blob: 03f779ad8a4d2957bc72447c7ca17b2863120338
| 1 | /* |
| 2 | * Lagged Fibonacci PRNG |
| 3 | * Copyright (c) 2008 Michael Niedermayer |
| 4 | * |
| 5 | * This file is part of FFmpeg. |
| 6 | * |
| 7 | * FFmpeg is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of the GNU Lesser General Public |
| 9 | * License as published by the Free Software Foundation; either |
| 10 | * version 2.1 of the License, or (at your option) any later version. |
| 11 | * |
| 12 | * FFmpeg is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | * Lesser General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU Lesser General Public |
| 18 | * License along with FFmpeg; if not, write to the Free Software |
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 20 | */ |
| 21 | |
| 22 | #ifndef AVUTIL_LFG_H |
| 23 | #define AVUTIL_LFG_H |
| 24 | |
| 25 | #include <stdint.h> |
| 26 | |
| 27 | typedef struct AVLFG { |
| 28 | unsigned int state[64]; |
| 29 | int index; |
| 30 | } AVLFG; |
| 31 | |
| 32 | void av_lfg_init(AVLFG *c, unsigned int seed); |
| 33 | |
| 34 | /** |
| 35 | * Seed the state of the ALFG using binary data. |
| 36 | * |
| 37 | * Return value: 0 on success, negative value (AVERROR) on failure. |
| 38 | */ |
| 39 | int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length); |
| 40 | |
| 41 | /** |
| 42 | * Get the next random unsigned 32-bit number using an ALFG. |
| 43 | * |
| 44 | * Please also consider a simple LCG like state= state*1664525+1013904223, |
| 45 | * it may be good enough and faster for your specific use case. |
| 46 | */ |
| 47 | static inline unsigned int av_lfg_get(AVLFG *c){ |
| 48 | c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; |
| 49 | return c->state[c->index++ & 63]; |
| 50 | } |
| 51 | |
| 52 | /** |
| 53 | * Get the next random unsigned 32-bit number using a MLFG. |
| 54 | * |
| 55 | * Please also consider av_lfg_get() above, it is faster. |
| 56 | */ |
| 57 | static inline unsigned int av_mlfg_get(AVLFG *c){ |
| 58 | unsigned int a= c->state[(c->index-55) & 63]; |
| 59 | unsigned int b= c->state[(c->index-24) & 63]; |
| 60 | return c->state[c->index++ & 63] = 2*a*b+a+b; |
| 61 | } |
| 62 | |
| 63 | /** |
| 64 | * Get the next two numbers generated by a Box-Muller Gaussian |
| 65 | * generator using the random numbers issued by lfg. |
| 66 | * |
| 67 | * @param out array where the two generated numbers are placed |
| 68 | */ |
| 69 | void av_bmg_get(AVLFG *lfg, double out[2]); |
| 70 | |
| 71 | #endif /* AVUTIL_LFG_H */ |
| 72 |