src/add-ons/media/plugins/mp4_reader/libMP4/BitParser.cpp

   1 /*
   2  * Copyright (c) 2010, David McPaul
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without modification,
   6  * are permitted provided that the following conditions are met:
   7  *
   8  *  * Redistributions of source code must retain the above copyright notice,
   9  *    this list of conditions and the following disclaimer.
  10  *  * Redistributions in binary form must reproduce the above copyright notice,
  11  *    this list of conditions and the following disclaimer in the documentation
  12  *    and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  16  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  18  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  19  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  21  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
  22  * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  23  * OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "BitParser.h"
  27
  28 #include <math.h>
  29
  30 BitParser::BitParser(uint8 *bits, uint32 bitLength) {
  31         this->bits = bits;
  32         this->bitLength = bitLength;
  33         this->index = 0;
  34 }
  35
  36 BitParser::BitParser() {
  37         bits = NULL;
  38         bitLength = 0;
  39         index = 1;
  40 }
  41
  42 BitParser::~BitParser() {
  43         bits = NULL;
  44 }
  45
  46 void
  47 BitParser::Init(uint8 *bits, uint32 bitLength) {
  48         this->bits = bits;
  49         this->bitLength = bitLength;
  50         this->index = 1;
  51 }
  52
  53 void
  54 BitParser::Skip(uint8 length) {
  55         if (bitLength >= length) {
  56
  57                 while (length-- > 0) {
  58                         index++;
  59                         bitLength--;
  60
  61                         if (index > 8) {
  62                                 index = 1;
  63                                 bits++;
  64                         }
  65                 }
  66         }
  67 }
  68
  69 uint32
  70 BitParser::GetValue(uint8 length) {
  71         uint32 result = 0;
  72
  73         if (bitLength < length) {
  74                 return 0;
  75         }
  76
  77         while (length-- > 0) {
  78                 result = result << 1;
  79                 result += (*bits) & (uint8)(pow(2, 8-index)) ? 1 : 0;
  80                 index++;
  81                 bitLength--;
  82
  83                 if (index > 8) {
  84                         index = 1;
  85                         bits++;
  86                 }
  87         }
  88
  89         return result;
  90 }