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: check_crc.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 INPUT 33 34 35 OUTPUT 36 37 errorCode, noError if successful 38 39 ------------------------------------------------------------------------------ 40 FUNCTION DESCRIPTION 41 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 #include "check_crc.h" 90 91 /*---------------------------------------------------------------------------- 92 ; MACROS 93 ; Define module specific macros here 94 ----------------------------------------------------------------------------*/ 95 96 97 /*---------------------------------------------------------------------------- 98 ; DEFINES 99 ; Include all pre-processor statements here. Include conditional 100 ; compile variables also. 101 ----------------------------------------------------------------------------*/ 102 103 /*---------------------------------------------------------------------------- 104 ; LOCAL FUNCTION DEFINITIONS 105 ; Function Prototype declaration 106 ----------------------------------------------------------------------------*/ 107 108 /*---------------------------------------------------------------------------- 109 ; LOCAL STORE/BUFFER/POINTER DEFINITIONS 110 ; Variable declaration - defined here and used outside this module 111 ----------------------------------------------------------------------------*/ 112 113 /*---------------------------------------------------------------------------- 114 ; EXTERNAL FUNCTION REFERENCES 115 ; Declare functions defined elsewhere and referenced in this module 116 ----------------------------------------------------------------------------*/ 117 118 /*---------------------------------------------------------------------------- 119 ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES 120 ; Declare variables used in this module but defined elsewhere 121 ----------------------------------------------------------------------------*/ 122 123 /*---------------------------------------------------------------------------- 124 ; FUNCTION CODE 125 ----------------------------------------------------------------------------*/ 126 127 void check_crc(HANDLE_CRC hCrcBuf, UInt32 bValue, Int32 nBits) 128 { 129 Int32 i; 130 UInt32 bMask = (1UL << (nBits - 1)); 131 132 for (i = 0; i < nBits; i++, bMask >>= 1) 133 { 134 UInt16 flag = (UInt16)((hCrcBuf->crcState & hCrcBuf->crcMask) ? 1 : 0); 135 UInt16 flag1 = (UInt16)((bMask & bValue) ? 1 : 0); 136 137 flag ^= flag1; 138 hCrcBuf->crcState <<= 1; 139 if (flag) 140 hCrcBuf->crcState ^= hCrcBuf->crcPoly; 141 } 142 143 } 144 145
