ffmpeg.libavutil.lfg source code

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 module ffmpeg.libavutil.lfg;
22 extern (C) @nogc nothrow:
23 
24 /**
25  * Context structure for the Lagged Fibonacci PRNG.
26  * The exact layout, types and content of this struct may change and should
27  * not be accessed directly. Only its sizeof() is guranteed to stay the same
28  * to allow easy instanciation.
29  */
30 struct AVLFG
31 {
32     uint[64] state;
33     int index;
34 }
35 
36 void av_lfg_init (AVLFG* c, uint seed);
37 
38 /**
39  * Seed the state of the ALFG using binary data.
40  *
41  * Return value: 0 on success, negative value (AVERROR) on failure.
42  */
43 int av_lfg_init_from_data (AVLFG* c, const(ubyte)* data, uint length);
44 
45 /**
46  * Get the next random unsigned 32-bit number using an ALFG.
47  *
48  * Please also consider a simple LCG like state= state*1664525+1013904223,
49  * it may be good enough and faster for your specific use case.
50  */
51 uint av_lfg_get (AVLFG* c);
52 
53 /**
54  * Get the next random unsigned 32-bit number using a MLFG.
55  *
56  * Please also consider av_lfg_get() above, it is faster.
57  */
58 uint av_mlfg_get (AVLFG* c);
59 
60 /**
61  * Get the next two numbers generated by a Box-Muller Gaussian
62  * generator using the random numbers issued by lfg.
63  *
64  * @param out array where the two generated numbers are placed
65  */
66 void av_bmg_get (AVLFG* lfg, ref double[2] out_);
67 
68 /* AVUTIL_LFG_H */