#include <fstream>
#include <FastCRC.h>

using namespace std;
using namespace FastCRC;

const unsigned int BUFF_SIZE = 1024;

int main()
{
    fstream file( "c:\\test.txt", ios::in | ios::binary );

    if( !file )
        return 1;

    unsigned char buff[ BUFF_SIZE ];
 
    //Instantiate a CFastCRC16 object

    CFastCRC16 crcobj;

    //Calculate the checksum by calling Update for each block of the file

    while( !file.eof() )
    { 
        file.read( ( char* )buff, BUFF_SIZE );
        crcobj.Update( buff, file.gcount() );
    }

    //Do final changes and get the checksum

    unsigned long checksum = crcobj.Final();

    //Use the checksum
    //...

    file.close();

    return 0;
}