hex_comp.cpp

/* Copyright (C) 2018, Project Pluto

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.

   This is a small test program that really shouldn't have been
posted.  There are probably perfectly decent utilities for this
purpose,  but it was easy enough to write this up... it does
absolutely nothing except read two binary files and display where
they differ.    */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

int main( const int argc, const char **argv)
{
   FILE *ifile1 = fopen( argv[1], "rb");
   FILE *ifile2 = fopen( argv[2], "rb");
   size_t bytes_read1, bytes_read2, loc = 0;
   const size_t buffsize = 32768;
   unsigned char *ibuff1 = (unsigned char *)malloc( buffsize * 2);
   unsigned char *ibuff2 = ibuff1 + buffsize;

   assert( ifile1);
   assert( ifile2);
   assert( ibuff1);
   while( (bytes_read1 = fread( ibuff1, 1, buffsize, ifile1)) != 0 &&
          (bytes_read2 = fread( ibuff2, 1, buffsize, ifile2)) != 0)
      {
      size_t i;

      assert( bytes_read1 == bytes_read2);
      if( memcmp( ibuff1, ibuff2, bytes_read1))
         for( i = 0; i < bytes_read1; i++)
            if( ibuff1[i] != ibuff2[i])
               printf( "%8lx: %02x %02x %zd\n",
                           loc + i, ibuff1[i], ibuff2[i], loc + i);
      loc += bytes_read1;
      }
   return( 0);
}