Calculating CRC Checksums in C++

Figure 2: A program that uses the CRCGenerator class

#include <iostream>
#include <fstream>
#include <iterator>

using namespace std;
#include "crc.h"

int main( int argc, char* argv[] )
   {
   if( argc < 2 )
      {
      cerr << "Usage: CRC16 file1 file2...\n";
      return 1;
      }
   typedef cdm_crc::CRCGenerator<16, 0x8005, 0, 0, true> CRC16;
   CRC16 crc16;
   cout.setf( ios_base::hex, ios_base::basefield );
   cout.setf( ios_base::showbase );
   for( int i = 1; i < argc; i++ )
      {
      ifstream infile( argv[i] );
      infile.unsetf( ios_base::skipws );
      if( !infile )
         {
         cerr << "Error: unable to open " << argv[i] << '\n';
         continue;
         }
      crc16.Process( istream_iterator<unsigned char>( infile ),
         istream_iterator<unsigned char>() );
      unsigned long ncrcVal = crc16.GetNormalCRC();
      ncrcVal >>= (cdm_crc::CRCMaxBits-crc16.GetWidth() );
      cout << "File: " << argv[i] << '\t' 
           << "CRC-16 checksum: " << ncrcVal << '\n';
      }
   return 0;
   }