LCOV - code coverage report
Current view: top level - libavutil - lfg.c (source / functions) Hit Total Coverage
Test: coverage.info Lines: 21 33 63.6 %
Date: 2017-12-15 02:19:58 Functions: 2 3 66.7 %

          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 "crc.h"
      27             : #include "md5.h"
      28             : #include "error.h"
      29             : #include "intreadwrite.h"
      30             : #include "attributes.h"
      31             : 
      32         421 : av_cold void av_lfg_init(AVLFG *c, unsigned int seed)
      33             : {
      34         421 :     uint8_t tmp[16] = { 0 };
      35             :     int i;
      36             : 
      37        6315 :     for (i = 8; i < 64; i += 4) {
      38        5894 :         AV_WL32(tmp, seed);
      39        5894 :         tmp[4] = i;
      40        5894 :         av_md5_sum(tmp, tmp, 16);
      41        5894 :         c->state[i    ] = AV_RL32(tmp);
      42        5894 :         c->state[i + 1] = AV_RL32(tmp + 4);
      43        5894 :         c->state[i + 2] = AV_RL32(tmp + 8);
      44        5894 :         c->state[i + 3] = AV_RL32(tmp + 12);
      45             :     }
      46         421 :     c->index = 0;
      47         421 : }
      48             : 
      49       19765 : void av_bmg_get(AVLFG *lfg, double out[2])
      50             : {
      51             :     double x1, x2, w;
      52             : 
      53             :     do {
      54       19765 :         x1 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0;
      55       19765 :         x2 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0;
      56       19765 :         w  = x1 * x1 + x2 * x2;
      57       19765 :     } while (w >= 1.0);
      58             : 
      59       15476 :     w = sqrt((-2.0 * log(w)) / w);
      60       15476 :     out[0] = x1 * w;
      61       15476 :     out[1] = x2 * w;
      62       15476 : }
      63             : 
      64           0 : int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length) {
      65             :     unsigned int beg, end, segm;
      66             :     const AVCRC *avcrc;
      67           0 :     uint32_t crc = 1;
      68             : 
      69             :     /* avoid integer overflow in the loop below. */
      70           0 :     if (length > (UINT_MAX / 128U)) return AVERROR(EINVAL);
      71             : 
      72           0 :     c->index = 0;
      73           0 :     avcrc = av_crc_get_table(AV_CRC_32_IEEE); /* This can't fail. It's a well-defined table in crc.c */
      74             : 
      75             :     /* across 64 segments of the incoming data,
      76             :      * do a running crc of each segment and store the crc as the state for that slot.
      77             :      * this works even if the length of the segment is 0 bytes. */
      78           0 :     beg = 0;
      79           0 :     for (segm = 0;segm < 64;segm++) {
      80           0 :         end = (((segm + 1) * length) / 64);
      81           0 :         crc = av_crc(avcrc, crc, data + beg, end - beg);
      82           0 :         c->state[segm] = (unsigned int)crc;
      83           0 :         beg = end;
      84             :     }
      85             : 
      86           0 :     return 0;
      87             : }

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