Collection of different CRC calculations
Work in Progress
crc.cpp
- Committer:
- sam_grove
- Date:
- 2013-05-14
- Revision:
- 1:ec8513f94d23
- Parent:
- 0:28e16d33040f
File content as of revision 1:ec8513f94d23:
#define CRC32_POLYNOMIAL 0xEDB88320L
void CRC32Value(unsigned long &CRC, 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 = ( CRC >> 8 ) & 0x00FFFFFFL;
unsigned long ulCRC = ((int) CRC ^ c ) & 0xff ;
for (int j = 8 ; j > 0; j-- )
{
if ( ulCRC & 1 )
{
ulCRC = ( ulCRC >> 1 ) ^ CRC32_POLYNOMIAL;
}
else
{
ulCRC >>= 1;
}
}
CRC = 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 );
}
*/
Sam Grove