FFmpeg coverage


Directory: ../../../ffmpeg/
File: src/libavutil/lfg.h
Date: 2024-02-16 17:37:06
Exec Total Coverage
Lines: 4 4 100.0%
Functions: 1 1 100.0%
Branches: 0 0 -%

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 353429490 static inline unsigned int av_lfg_get(AVLFG *c){
54 353429490 unsigned a = c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
55 353429490 c->index += 1U;
56 353429490 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