Using XOR Bitwise Operation to Performa a Byte-By-Byte Comparison

Question

I would like to take two files, compare them byte-by-byte, and test it's performance,

So far, this is what my code looks like:

#include<stdio.h>
#include <time.h>

int main()
{
    FILE *fp1, *fp2;
    int ch1, ch2;
    char fname1[40], fname2[40] ;

    printf("Enter name of first file :") ;
    gets(fname1);

    printf("Enter name of second file:");
    gets(fname2);

    clock();    

    fp1 = fopen( fname1,  "r" );
    fp2 = fopen( fname2,  "r" ) ;

    if ( fp1 == NULL )
    {
        printf("Cannot open %s for reading\n", fname1 );
        exit(1);
    }
    else if (fp2 == NULL)
    {
        printf("Cannot open %s for reading\n", fname2 );
        exit(1);
    }
    else
    {
        ch1  =  getc( fp1 ) ;
        ch2  =  getc( fp2 ) ;

        while( (ch1!=EOF) && (ch2!=EOF) && (ch1 == ch2))
        {
            ch1 = getc(fp1);
            ch2 = getc(fp2);
        }

        if (ch1 == ch2)
            printf("Files are identical\n");
        else if (ch1 != ch2)
            printf("Files are Not identical\n");

        fclose ( fp1 );
        fclose ( fp2 );
    }

    printf("That took %d seconds.\n", clock() / CLOCKS_PER_SEC);

    return 0;
}

This code compares two files if they are identical, but I would like to check by using the bitwise operation of XOR, any ideas of how I can do this?

Is there any way I can read in a file one byte at a time?

Thanks for your help in advance!

Answer 1

How about taking your code exactly as it is and changing this in your main loop?

 while( (ch1!=EOF) && (ch2!=EOF) && !(ch1 ^ ch2))
 {
    ch1 = getc(fp1);
    ch2 = getc(fp2);
 }

Quick note: You're already reading the file byte by byte. getc() is reading only a character from the file but you then store it as an int. From getc() function's description: On success, the character read is returned (promoted to an int value).