A simple CRC library used to verify configuration data
Fork of CRC by
crc.cpp
- Committer:
- SomeRandomBloke
- Date:
- 2016-10-03
- Revision:
- 3:599d283e5a44
- Parent:
- 2:53b7db1f47ea
File content as of revision 3:599d283e5a44:
/** crc.cpp * * @license * MIT License * * Copyright (c) 2016 Andrew D Lindsay/Thing Innovations https://thinginnovations.uk * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all * copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. * */ #define CRC32_POLYNOMIAL 0xEDB88320L void CRC32Value(unsigned long &CRCval, unsigned char c) { ///////////////////////////////////////////////////////////////////////////////////// //CRC must be initialized as zero //c is a character from the sequence that is used to form the CRC //this code is a modification of the code from the Novatel OEM615 specification ///////////////////////////////////////////////////////////////////////////////////// unsigned long ulTemp1 = ( CRCval >> 8 ) & 0x00FFFFFFL; unsigned long ulCRC = ((int) CRCval ^ c ) & 0xff ; for (int j = 8 ; j > 0; j-- ) { if ( ulCRC & 1 ) { ulCRC = ( ulCRC >> 1 ) ^ CRC32_POLYNOMIAL; } else { ulCRC >>= 1; } } CRCval = ulTemp1 ^ ulCRC; } /* -------------------------------------------------------------------------- Calculates the CRC-32 of a block of data all at once //the CRC is from the complete message (header plus data) //but excluding (of course) the CRC at the end -------------------------------------------------------------------------- */ unsigned long CalculateBlockCRC32( unsigned long ulCount, /* Number of bytes in the data block */ unsigned char *ucBuffer ) /* Data block */ { ////////////////////////////////////////////////////////////////////// //the below code tests the CRC32Value procedure used in a markov form ////////////////////////////////////////////////////////////////////// unsigned long CRC = 0; for (int i = 0; i<ulCount; i++) { CRC32Value( CRC, *ucBuffer++ ); } return CRC; } /* unsigned long CalculateBlockCRC32( unsigned long ulCount, unsigned char *ucBuffer ) { //////////////////////////////////////////// //original code from the OEM615 manual //////////////////////////////////////////// unsigned long ulTemp1; unsigned long ulTemp2; unsigned long ulCRC = 0; while ( ulCount-- != 0 ) { ulTemp1 = ( ulCRC >> 8 ) & 0x00FFFFFFL; ulTemp2 = CRC32Value( ((int) ulCRC ^ *ucBuffer++ ) & 0xff ); ulCRC = ulTemp1 ^ ulTemp2; } return( ulCRC ); } */