#include <stdio.h>

/*
 * SUM -- Compute the BSD checksum of a file or files.
 */
main (argc,argv)
int	argc;
char	**argv;
{
	register unsigned sum;
	register i, c;
	register FILE *f;
	register long nbytes;
	int	errflg = 0;

	i = 1;
	do {
	    if (i < argc) {
		if ((f = fopen(argv[i], "r")) == NULL) {
		    fprintf (stderr, "sum: Can't open %s\n", argv[i]);
		    errflg += 10;
		    continue;
		}
	    } else
		f = stdin;

	    sum = 0;
	    nbytes = 0;
	    while ((c = getc(f)) != EOF) {
		nbytes++;
		if (sum&01)
		    sum = (sum>>1) + 0x8000;
		else
		    sum >>= 1;
		sum += c;
		sum &= 0xFFFF;
	    }
	    if (ferror (f)) {
		errflg++;
		fprintf (stderr, "sum: read error on %s\n", argc>1?argv[i]:"-");
	    }
	    printf ("%05u%6ld", sum, (nbytes+BUFSIZ-1)/BUFSIZ);
	    if (argc > 2)
		printf (" %s", argv[i]);
	    printf ("\n");
	    fclose (f);

	} while (++i < argc);

	exit (errflg);
}