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libavutil/lfg.h

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00001 /*
00002  * Lagged Fibonacci PRNG
00003  * Copyright (c) 2008 Michael Niedermayer
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #ifndef AVUTIL_LFG_H
00023 #define AVUTIL_LFG_H
00024 
00025 typedef struct {
00026     unsigned int state[64];
00027     int index;
00028 } AVLFG;
00029 
00030 void av_lfg_init(AVLFG *c, unsigned int seed);
00031 
00038 static inline unsigned int av_lfg_get(AVLFG *c){
00039     c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
00040     return c->state[c->index++ & 63];
00041 }
00042 
00048 static inline unsigned int av_mlfg_get(AVLFG *c){
00049     unsigned int a= c->state[(c->index-55) & 63];
00050     unsigned int b= c->state[(c->index-24) & 63];
00051     return c->state[c->index++ & 63] = 2*a*b+a+b;
00052 }
00053 
00060 void av_bmg_get(AVLFG *lfg, double out[2]);
00061 
00062 #endif /* AVUTIL_LFG_H */

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