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 INPUT AND OUTPUT DEFINITIONS 21 22 Inputs: 23 pInputStream = pointer to a BITS structure that holds information 24 regarding the input stream. 25 26 Local Stores/Buffers/Pointers Needed: 27 None 28 29 Global Stores/Buffers/Pointers Needed: 30 None 31 32 Outputs: 33 None 34 35 Pointers and Buffers Modified: 36 pInputStream->usedBits is rounded up to a number that represents the next 37 byte boundary. 38 39 Local Stores Modified: 40 None 41 42 Global Stores Modified: 43 None 44 45 ------------------------------------------------------------------------------ 46 FUNCTION DESCRIPTION 47 48 Makes the input stream structure pointed to align to the next byte boundary. 49 If it is already at a byte boundary it is left alone. 50 51 ------------------------------------------------------------------------------ 52 REQUIREMENTS 53 54 This function shall not use global or static variables. 55 56 ------------------------------------------------------------------------------ 57 REFERENCES 58 59 (1) MPEG-2 NBC Audio Decoder 60 "This software module was originally developed by AT&T, Dolby 61 Laboratories, Fraunhofer Gesellschaft IIS in the course of development 62 of the MPEG-2 NBC/MPEG-4 Audio standard ISO/IEC 13818-7, 14496-1,2 and 63 3. This software module is an implementation of a part of one or more 64 MPEG-2 NBC/MPEG-4 Audio tools as specified by the MPEG-2 NBC/MPEG-4 65 Audio standard. ISO/IEC gives users of the MPEG-2 NBC/MPEG-4 Audio 66 standards free license to this software module or modifications thereof 67 for use in hardware or software products claiming conformance to the 68 MPEG-2 NBC/MPEG-4 Audio standards. Those intending to use this software 69 module in hardware or software products are advised that this use may 70 infringe existing patents. The original developer of this software 71 module and his/her company, the subsequent editors and their companies, 72 and ISO/IEC have no liability for use of this software module or 73 modifications thereof in an implementation. Copyright is not released 74 for non MPEG-2 NBC/MPEG-4 Audio conforming products.The original 75 developer retains full right to use the code for his/her own purpose, 76 assign or donate the code to a third party and to inhibit third party 77 from using the code for non MPEG-2 NBC/MPEG-4 Audio conforming products. 78 This copyright notice must be included in all copies or derivative 79 works." 80 Copyright(c)1996. 81 82 ------------------------------------------------------------------------------ 83 PSEUDO-CODE 84 85 void byte_align( 86 BITS *pInputStream) 87 88 MODIFYING(pInputStream->usedBits = pInputStream->usedBits + 89 (pInputStream->usedBits + 7) % 8) 90 91 RETURN(nothing) 92 93 ------------------------------------------------------------------------------ 94 RESOURCES USED 95 96 STACK USAGE: 97 98 where: 99 100 DATA MEMORY USED: x words 101 102 PROGRAM MEMORY USED: x words 103 104 CLOCK CYCLES: 105 106 ------------------------------------------------------------------------------ 107 */ 108 109 110 /*---------------------------------------------------------------------------- 111 ; INCLUDES 112 ----------------------------------------------------------------------------*/ 113 114 115 116 #include "pv_audio_type_defs.h" 117 #include "s_bits.h" 118 #include "ibstream.h" 119 120 /*---------------------------------------------------------------------------- 121 ; MACROS 122 ; Define module specific macros here 123 ----------------------------------------------------------------------------*/ 124 125 /*---------------------------------------------------------------------------- 126 ; DEFINES 127 ; Include all pre-processor statements here. Include conditional 128 ; compile variables also. 129 ----------------------------------------------------------------------------*/ 130 131 /* 132 * A negative number was used for this mask so that it works on both 133 * 16-bit or 32-bit machines. The mask must be cast to unsigned int to 134 * work with TI compiler, ver 1.80. 135 */ 136 #define BYTE_ALIGN_MASK ((UInt)(-8)) 137 138 #define BYTE_ALIGN_ROUNDUP 7 139 140 /*---------------------------------------------------------------------------- 141 ; LOCAL FUNCTION DEFINITIONS 142 ; Function Prototype declaration 143 ----------------------------------------------------------------------------*/ 144 145 /*---------------------------------------------------------------------------- 146 ; LOCAL VARIABLE DEFINITIONS 147 ; Variable declaration - defined here and used outside this module 148 ----------------------------------------------------------------------------*/ 149 150 /*---------------------------------------------------------------------------- 151 ; EXTERNAL FUNCTION REFERENCES 152 ; Declare functions defined elsewhere and referenced in this module 153 ----------------------------------------------------------------------------*/ 154 155 /*---------------------------------------------------------------------------- 156 ; EXTERNAL VARIABLES REFERENCES 157 ; Declare variables used in this module but defined elsewhere 158 ----------------------------------------------------------------------------*/ 159 160 /*---------------------------------------------------------------------------- 161 ; FUNCTION CODE 162 ----------------------------------------------------------------------------*/ 163 void byte_align( 164 BITS *pInputStream) 165 { 166 /* 167 * Round up to the next byte by adding 7 and masking off with 168 * FFF8 or FFFFFFF8. The masking operation is a faster way to 169 * perform modulo arithmetic if the number is a power of 2. 170 * 171 * This code is the same as 172 * pInputStream->usedBits += (pInputStream->usedBits + 7) % 8 173 */ 174 pInputStream->usedBits += BYTE_ALIGN_ROUNDUP; 175 pInputStream->usedBits &= BYTE_ALIGN_MASK; 176 177 return; 178 } 179 180
