+ const char *p;
+ off_t count = 0;
+ int negative;
+
+ /* Parse count_string, taking care to check for overflow.
+ We can't use standard functions,
+ since off_t might be longer than long. */
+
+ for (p = count_string; *p == ' ' || *p == '\t'; p++)
+ continue;
+
+ negative = *p == '-';
+ p += negative || *p == '+';
+
+ for (;;)
+ {
+ int digit = *p++ - '0';
+ if (9 < (unsigned) digit)
+ break;
+ else
+ {
+ off_t c10 = 10 * count;
+ off_t nc = negative ? c10 - digit : c10 + digit;
+ if (c10 / 10 != count || (negative ? c10 < nc : nc < c10))
+ {
+ report_error_message (N_("Seek offset out of range"));
+ exit (EXIT_FAILURE);
+ }
+ count = nc;
+ }
+ }
+
+ mtop.mt_count = count;
+ if (mtop.mt_count != count)
+ {
+ report_error_message (N_("Seek offset out of range"));
+ exit (EXIT_FAILURE);
+ }