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
50SC 29 Software Copyright Licencing Disclaimer:
51
52This software module was originally developed by
53  Coding Technologies
54
55and edited by
56  -
57
58in the course of development of the ISO/IEC 13818-7 and ISO/IEC 14496-3
59standards for reference purposes and its performance may not have been
60optimized. This software module is an implementation of one or more tools as
61specified by the ISO/IEC 13818-7 and ISO/IEC 14496-3 standards.
62ISO/IEC gives users free license to this software module or modifications
63thereof for use in products claiming conformance to audiovisual and
64image-coding related ITU Recommendations and/or ISO/IEC International
65Standards. ISO/IEC gives users the same free license to this software module or
66modifications thereof for research purposes and further ISO/IEC standardisation.
67Those intending to use this software module in products are advised that its
68use may infringe existing patents. ISO/IEC have no liability for use of this
69software module or modifications thereof. Copyright is not released for
70products that do not conform to audiovisual and image-coding related ITU
71Recommendations and/or ISO/IEC International Standards.
72The original developer retains full right to modify and use the code for its
73own purpose, assign or donate the code to a third party and to inhibit third
74parties from using the code for products that do not conform to audiovisual and
75image-coding related ITU Recommendations and/or ISO/IEC International Standards.
76This copyright notice must be included in all copies or derivative works.
77Copyright (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
127void 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