/*
**  CHKABS.C
**
**  PROGRAM TO VERIFY THE CHECKSUMS OF AN HP 21xx ABSOLUTE BINARY TAPE
*/
#include <stdio.h>

main (argc, argv) 
int argc;
char *argv[];
{
    FILE *fp;
    int done, ii, count, maxnull, dummy, nbchecked;
    unsigned short sum, addr, data;

    if (argc != 2) {
        printf ("Usage: chkabs filename\n");
        exit (-1);
    }
    fp = fopen (argv[1], "rb");
    if (!fp) {
        printf ("Can't open file %s\n", argv[1]);
        exit (-1);
    }
    nbchecked = 0;
    maxnull = 10000;
    done = 0;
    while (!done) {
        count = fgetc (fp);
        if (count == EOF) {
            printf ("Unexpected EOF!\n");   
            done = 1;
        } else if (!count) {
            maxnull--;
            if (!maxnull) done=1;
        } else {
            dummy = fgetc (fp);
            addr = (fgetc(fp) << 8) | fgetc(fp);
            sum = addr;
            for (ii=0; ii<count; ii++) {
                data = (fgetc(fp) << 8) | fgetc(fp);
                sum = sum + data;
                nbchecked++;
            }
            data = (fgetc(fp) << 8) | fgetc(fp);
            if (sum != data) {
                printf ("Checksum Error!\n");
                done = 1;
            } else {
                maxnull = 10;
            }
        }
    }
    printf ("%d words checked\n", nbchecked);
}