LCOV - code coverage report
Current view: top level - src/libavutil - lfg.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 21 21 100.0 %
Date: 2017-01-21 09:32:20 Functions: 2 2 100.0 %

          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             : #include <inttypes.h>
      23             : #include <limits.h>
      24             : #include <math.h>
      25             : #include "lfg.h"
      26             : #include "md5.h"
      27             : #include "intreadwrite.h"
      28             : #include "attributes.h"
      29             : 
      30         361 : av_cold void av_lfg_init(AVLFG *c, unsigned int seed)
      31             : {
      32         361 :     uint8_t tmp[16] = { 0 };
      33             :     int i;
      34             : 
      35        5415 :     for (i = 8; i < 64; i += 4) {
      36        5054 :         AV_WL32(tmp, seed);
      37        5054 :         tmp[4] = i;
      38        5054 :         av_md5_sum(tmp, tmp, 16);
      39        5054 :         c->state[i    ] = AV_RL32(tmp);
      40        5054 :         c->state[i + 1] = AV_RL32(tmp + 4);
      41        5054 :         c->state[i + 2] = AV_RL32(tmp + 8);
      42        5054 :         c->state[i + 3] = AV_RL32(tmp + 12);
      43             :     }
      44         361 :     c->index = 0;
      45         361 : }
      46             : 
      47         781 : void av_bmg_get(AVLFG *lfg, double out[2])
      48             : {
      49             :     double x1, x2, w;
      50             : 
      51             :     do {
      52         781 :         x1 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0;
      53         781 :         x2 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0;
      54         781 :         w  = x1 * x1 + x2 * x2;
      55         781 :     } while (w >= 1.0);
      56             : 
      57         600 :     w = sqrt((-2.0 * log(w)) / w);
      58         600 :     out[0] = x1 * w;
      59         600 :     out[1] = x2 * w;
      60         600 : }

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