mirror of
https://git.ffmpeg.org/ffmpeg.git
synced 2024-12-21 06:50:44 +00:00
82 lines
2.5 KiB
C
82 lines
2.5 KiB
C
/*
|
|
* Lagged Fibonacci PRNG
|
|
* Copyright (c) 2008 Michael Niedermayer
|
|
*
|
|
* 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
|
|
*/
|
|
|
|
#ifndef AVUTIL_LFG_H
|
|
#define AVUTIL_LFG_H
|
|
|
|
#include <stdint.h>
|
|
|
|
/**
|
|
* Context structure for the Lagged Fibonacci PRNG.
|
|
* The exact layout, types and content of this struct may change and should
|
|
* not be accessed directly. Only its `sizeof()` is guaranteed to stay the same
|
|
* to allow easy instanciation.
|
|
*/
|
|
typedef struct AVLFG {
|
|
unsigned int state[64];
|
|
int index;
|
|
} AVLFG;
|
|
|
|
void av_lfg_init(AVLFG *c, unsigned int seed);
|
|
|
|
/**
|
|
* Seed the state of the ALFG using binary data.
|
|
*
|
|
* @return 0 on success, negative value (AVERROR) on failure.
|
|
*/
|
|
int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length);
|
|
|
|
/**
|
|
* Get the next random unsigned 32-bit number using an ALFG.
|
|
*
|
|
* Please also consider a simple LCG like state= state*1664525+1013904223,
|
|
* it may be good enough and faster for your specific use case.
|
|
*/
|
|
static inline unsigned int av_lfg_get(AVLFG *c){
|
|
unsigned a = c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
|
|
c->index += 1U;
|
|
return a;
|
|
}
|
|
|
|
/**
|
|
* Get the next random unsigned 32-bit number using a MLFG.
|
|
*
|
|
* Please also consider av_lfg_get() above, it is faster.
|
|
*/
|
|
static inline unsigned int av_mlfg_get(AVLFG *c){
|
|
unsigned int a= c->state[(c->index-55) & 63];
|
|
unsigned int b= c->state[(c->index-24) & 63];
|
|
a = c->state[c->index & 63] = 2*a*b+a+b;
|
|
c->index += 1U;
|
|
return a;
|
|
}
|
|
|
|
/**
|
|
* Get the next two numbers generated by a Box-Muller Gaussian
|
|
* generator using the random numbers issued by lfg.
|
|
*
|
|
* @param lfg pointer to the contex structure
|
|
* @param out array where the two generated numbers are placed
|
|
*/
|
|
void av_bmg_get(AVLFG *lfg, double out[2]);
|
|
|
|
#endif /* AVUTIL_LFG_H */
|