/usr/include/libavutil/lfg.h is in libavutil-dev 4:0.8.17-0ubuntu0.12.04.2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 | /*
* Lagged Fibonacci PRNG
* Copyright (c) 2008 Michael Niedermayer
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; 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);
/**
* 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){
c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
return c->state[c->index++ & 63];
}
/**
* 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];
return c->state[c->index++ & 63] = 2*a*b+a+b;
}
/**
* Get the next two numbers generated by a Box-Muller Gaussian
* generator using the random numbers issued by lfg.
*
* @param out array where the two generated numbers are placed
*/
void av_bmg_get(AVLFG *lfg, double out[2]);
#endif /* AVUTIL_LFG_H */
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