FFmpeg/libavutil/lfg.h
Stefano Sabatini 987903826b Globally rename the header inclusion guard names.
Consistently apply this rule: the guard name is obtained from the
filename by stripping the leading "lib", converting '/' and '.'  to
'_' and uppercasing the resulting name. Guard names in the root
directory have to be prefixed by "FFMPEG_".

Originally committed as revision 15120 to svn://svn.ffmpeg.org/ffmpeg/trunk
2008-08-31 07:39:47 +00:00

55 lines
1.7 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
typedef struct {
unsigned int state[64];
int index;
} AVLFG;
void av_lfg_init(AVLFG *c, unsigned int seed);
/**
* Gets the next random unsigned 32bit number using a 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){
c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
return c->state[c->index++ & 63];
}
/**
* Gets the next random unsigned 32bit number using a MLFG.
*
* Please also consider the 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];
return c->state[c->index++ & 63] = 2*a*b+a+b;
}
#endif /* AVUTIL_LFG_H */