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 );
}
*/