| Line | Branch | Exec | Source |
|---|---|---|---|
| 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 | /** | ||
| 28 | * Context structure for the Lagged Fibonacci PRNG. | ||
| 29 | * The exact layout, types and content of this struct may change and should | ||
| 30 | * not be accessed directly. Only its `sizeof()` is guaranteed to stay the same | ||
| 31 | * to allow easy instanciation. | ||
| 32 | */ | ||
| 33 | typedef struct AVLFG { | ||
| 34 | unsigned int state[64]; | ||
| 35 | int index; | ||
| 36 | } AVLFG; | ||
| 37 | |||
| 38 | void av_lfg_init(AVLFG *c, unsigned int seed); | ||
| 39 | |||
| 40 | /** | ||
| 41 | * Seed the state of the ALFG using binary data. | ||
| 42 | * | ||
| 43 | * @return 0 on success, negative value (AVERROR) on failure. | ||
| 44 | */ | ||
| 45 | int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length); | ||
| 46 | |||
| 47 | /** | ||
| 48 | * Get the next random unsigned 32-bit number using an ALFG. | ||
| 49 | * | ||
| 50 | * Please also consider a simple LCG like state= state*1664525+1013904223, | ||
| 51 | * it may be good enough and faster for your specific use case. | ||
| 52 | */ | ||
| 53 | 357870622 | static inline unsigned int av_lfg_get(AVLFG *c){ | |
| 54 | 357870622 | unsigned a = c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; | |
| 55 | 357870622 | c->index += 1U; | |
| 56 | 357870622 | return a; | |
| 57 | } | ||
| 58 | |||
| 59 | /** | ||
| 60 | * Get the next random unsigned 32-bit number using a MLFG. | ||
| 61 | * | ||
| 62 | * Please also consider av_lfg_get() above, it is faster. | ||
| 63 | */ | ||
| 64 | static inline unsigned int av_mlfg_get(AVLFG *c){ | ||
| 65 | unsigned int a= c->state[(c->index-55) & 63]; | ||
| 66 | unsigned int b= c->state[(c->index-24) & 63]; | ||
| 67 | a = c->state[c->index & 63] = 2*a*b+a+b; | ||
| 68 | c->index += 1U; | ||
| 69 | return a; | ||
| 70 | } | ||
| 71 | |||
| 72 | /** | ||
| 73 | * Get the next two numbers generated by a Box-Muller Gaussian | ||
| 74 | * generator using the random numbers issued by lfg. | ||
| 75 | * | ||
| 76 | * @param lfg pointer to the contex structure | ||
| 77 | * @param out array where the two generated numbers are placed | ||
| 78 | */ | ||
| 79 | void av_bmg_get(AVLFG *lfg, double out[2]); | ||
| 80 | |||
| 81 | #endif /* AVUTIL_LFG_H */ | ||
| 82 |