libavutil/lfg.c

   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
  22 #include <inttypes.h>
  23 #include "lfg.h"
  24 #include "md5.h"
  25 #include "intreadwrite.h"
  26
  27 void av_cold av_lfg_init(AVLFG *c, unsigned int seed){
  28     uint8_t tmp[16]={0};
  29     int i;
  30
  31     for(i=8; i<64; i+=4){
  32         AV_WL32(tmp, seed); tmp[4]=i;
  33         av_md5_sum(tmp, tmp,  16);
  34         c->state[i  ]= AV_RL32(tmp);
  35         c->state[i+1]= AV_RL32(tmp+4);
  36         c->state[i+2]= AV_RL32(tmp+8);
  37         c->state[i+3]= AV_RL32(tmp+12);
  38     }
  39     c->index=0;
  40 }
  41
  42 #ifdef TEST
  43 #include "log.h"
  44 #include "common.h"
  45
  46 int main(void)
  47 {
  48     int x=0;
  49     int i, j;
  50     AVLFG state;
  51
  52     av_lfg_init(&state, 0xdeadbeef);
  53     for (j = 0; j < 10000; j++) {
  54         START_TIMER
  55         for (i = 0; i < 624; i++) {
  56 //            av_log(NULL,AV_LOG_ERROR, "%X\n", av_lfg_get(&state));
  57             x+=av_lfg_get(&state);
  58         }
  59         STOP_TIMER("624 calls of av_lfg_get");
  60     }
  61     av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x);
  62     return 0;
  63 }
  64 #endif