1 /* ------------------------------------------------------------------ 2 * Copyright (C) 1998-2009 PacketVideo 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either 13 * express or implied. 14 * See the License for the specific language governing permissions 15 * and limitations under the License. 16 * ------------------------------------------------------------------- 17 */ 18 /* 19 20 Filename: buf_getbits.c 21 22 ------------------------------------------------------------------------------ 23 REVISION HISTORY 24 25 26 Who: Date: MM/DD/YYYY 27 Description: 28 29 ------------------------------------------------------------------------------ 30 INPUT AND OUTPUT DEFINITIONS 31 32 Arguments: hBitBuf Handle to Bitbuffer 33 n Number of bits to read 34 35 Return: bits 36 37 38 ------------------------------------------------------------------------------ 39 FUNCTION DESCRIPTION 40 41 Reads n bits from Bitbuffer 42 43 ------------------------------------------------------------------------------ 44 REQUIREMENTS 45 46 47 ------------------------------------------------------------------------------ 48 REFERENCES 49 50 SC 29 Software Copyright Licencing Disclaimer: 51 52 This software module was originally developed by 53 Coding Technologies 54 55 and edited by 56 - 57 58 in the course of development of the ISO/IEC 13818-7 and ISO/IEC 14496-3 59 standards for reference purposes and its performance may not have been 60 optimized. This software module is an implementation of one or more tools as 61 specified by the ISO/IEC 13818-7 and ISO/IEC 14496-3 standards. 62 ISO/IEC gives users free license to this software module or modifications 63 thereof for use in products claiming conformance to audiovisual and 64 image-coding related ITU Recommendations and/or ISO/IEC International 65 Standards. ISO/IEC gives users the same free license to this software module or 66 modifications thereof for research purposes and further ISO/IEC standardisation. 67 Those intending to use this software module in products are advised that its 68 use may infringe existing patents. ISO/IEC have no liability for use of this 69 software module or modifications thereof. Copyright is not released for 70 products that do not conform to audiovisual and image-coding related ITU 71 Recommendations and/or ISO/IEC International Standards. 72 The original developer retains full right to modify and use the code for its 73 own purpose, assign or donate the code to a third party and to inhibit third 74 parties from using the code for products that do not conform to audiovisual and 75 image-coding related ITU Recommendations and/or ISO/IEC International Standards. 76 This copyright notice must be included in all copies or derivative works. 77 Copyright (c) ISO/IEC 2002. 78 79 ------------------------------------------------------------------------------ 80 PSEUDO-CODE 81 82 ------------------------------------------------------------------------------ 83 */ 84 85 86 /*---------------------------------------------------------------------------- 87 ; INCLUDES 88 ----------------------------------------------------------------------------*/ 89 90 #ifdef AAC_PLUS 91 92 #include "buf_getbits.h" 93 94 /*---------------------------------------------------------------------------- 95 ; MACROS 96 ; Define module specific macros here 97 ----------------------------------------------------------------------------*/ 98 99 100 /*---------------------------------------------------------------------------- 101 ; DEFINES 102 ; Include all pre-processor statements here. Include conditional 103 ; compile variables also. 104 ----------------------------------------------------------------------------*/ 105 106 /*---------------------------------------------------------------------------- 107 ; LOCAL FUNCTION DEFINITIONS 108 ; Function Prototype declaration 109 ----------------------------------------------------------------------------*/ 110 111 /*---------------------------------------------------------------------------- 112 ; LOCAL STORE/BUFFER/POINTER DEFINITIONS 113 ; Variable declaration - defined here and used outside this module 114 ----------------------------------------------------------------------------*/ 115 116 /*---------------------------------------------------------------------------- 117 ; EXTERNAL FUNCTION REFERENCES 118 ; Declare functions defined elsewhere and referenced in this module 119 ----------------------------------------------------------------------------*/ 120 121 /*---------------------------------------------------------------------------- 122 ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES 123 ; Declare variables used in this module but defined elsewhere 124 ----------------------------------------------------------------------------*/ 125 126 /*---------------------------------------------------------------------------- 127 ; FUNCTION CODE 128 ----------------------------------------------------------------------------*/ 129 130 UInt32 buf_getbits(BIT_BUFFER * hBitBuf, Int32 n) 131 { 132 133 /* read bits from MSB side */ 134 if (hBitBuf->buffered_bits <= 16) 135 { 136 hBitBuf->buffer_word = (hBitBuf->buffer_word << 16) | (*(hBitBuf->char_ptr++) << 8); 137 hBitBuf->buffer_word |= *(hBitBuf->char_ptr++); 138 hBitBuf->buffered_bits += 16; 139 } 140 141 hBitBuf->buffered_bits -= n; 142 hBitBuf->nrBitsRead += n; 143 144 return ((hBitBuf->buffer_word >> hBitBuf->buffered_bits) & ((1 << n) - 1)); 145 146 } 147 148 149 UInt32 buf_get_1bit(BIT_BUFFER * hBitBuf) 150 { 151 152 /* read bits from MSB side */ 153 if (hBitBuf->buffered_bits <= 16) 154 { 155 hBitBuf->buffer_word = (hBitBuf->buffer_word << 16) | (*(hBitBuf->char_ptr++) << 8); 156 hBitBuf->buffer_word |= *(hBitBuf->char_ptr++); 157 hBitBuf->buffered_bits += 16; 158 } 159 160 hBitBuf->buffered_bits--; 161 hBitBuf->nrBitsRead++; 162 163 return ((hBitBuf->buffer_word >> hBitBuf->buffered_bits) & 1); 164 165 } 166 167 #endif 168
