LCOV - code coverage report
Current view: top level - libavutil - lfg.h (source / functions) Hit Total Coverage
Test: coverage.info Lines: 3 3 100.0 %
Date: 2017-12-15 02:19:58 Functions: 1 1 100.0 %

          Line data    Source code
       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             : #ifndef AVUTIL_LFG_H
      23             : #define AVUTIL_LFG_H
      24             : 
      25             : #include <stdint.h>
      26             : 
      27             : typedef struct AVLFG {
      28             :     unsigned int state[64];
      29             :     int index;
      30             : } AVLFG;
      31             : 
      32             : void av_lfg_init(AVLFG *c, unsigned int seed);
      33             : 
      34             : /**
      35             :  * Seed the state of the ALFG using binary data.
      36             :  *
      37             :  * Return value: 0 on success, negative value (AVERROR) on failure.
      38             :  */
      39             : int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length);
      40             : 
      41             : /**
      42             :  * Get the next random unsigned 32-bit number using an ALFG.
      43             :  *
      44             :  * Please also consider a simple LCG like state= state*1664525+1013904223,
      45             :  * it may be good enough and faster for your specific use case.
      46             :  */
      47    61238608 : static inline unsigned int av_lfg_get(AVLFG *c){
      48    61238608 :     c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63];
      49    61238608 :     return c->state[c->index++ & 63];
      50             : }
      51             : 
      52             : /**
      53             :  * Get the next random unsigned 32-bit number using a MLFG.
      54             :  *
      55             :  * Please also consider av_lfg_get() above, it is faster.
      56             :  */
      57             : static inline unsigned int av_mlfg_get(AVLFG *c){
      58             :     unsigned int a= c->state[(c->index-55) & 63];
      59             :     unsigned int b= c->state[(c->index-24) & 63];
      60             :     return c->state[c->index++ & 63] = 2*a*b+a+b;
      61             : }
      62             : 
      63             : /**
      64             :  * Get the next two numbers generated by a Box-Muller Gaussian
      65             :  * generator using the random numbers issued by lfg.
      66             :  *
      67             :  * @param out array where the two generated numbers are placed
      68             :  */
      69             : void av_bmg_get(AVLFG *lfg, double out[2]);
      70             : 
      71             : #endif /* AVUTIL_LFG_H */

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