date and time created 90/05/16 11:30:33 by bostic

[unix-history] / usr / src / lib / libc / stdlib / strtoul.c

/*
* Copyright (c) 1990 Regents of the University of California.
* All rights reserved.
*
* %sccs.include.redist.c%
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)strtoul.c   5.1 (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

#include <limits.h>
#include <ctype.h>
#include <errno.h>

/*
* Convert a string to an unsigned long integer.
*
* Ignores `locale' stuff.  Assumes that the upper and lower case
* alphabets and digits are each contiguous.
*/
unsigned long
strtoul(nptr, endptr, base)
       char *nptr, **endptr;
       register int base;
{
       register char *s = nptr;
       register unsigned long acc;
       register int c;
       register unsigned long cutoff;
       register int neg = 0, any, cutlim;

       /*
        * See strtol for comments as to the logic used.
        */
       do {
               c = *s++;
       } while (isspace(c));
       if (c == '-') {
               neg = 1;
               c = *s++;
       } else if (c == '+')
               c = *s++;
       if ((base == 0 || base == 16) &&
           c == '0' && (*s == 'x' || *s == 'X')) {
               c = s[1];
               s += 2;
               base = 16;
       }
       if (base == 0)
               base = c == '0' ? 8 : 10;
       cutoff = (unsigned long)ULONG_MAX / (unsigned long)base;
       cutlim = (unsigned long)ULONG_MAX % (unsigned long)base;
       for (acc = 0, any = 0;; c = *s++) {
               if (isdigit(c))
                       c -= '0';
               else if (isalpha(c))
                       c -= isupper(c) ? 'A' - 10 : 'a' - 10;
               else
                       break;
               if (c >= base)
                       break;
               if (any < 0 || acc > cutoff || acc == cutoff && c > cutlim)
                       any = -1;
               else {
                       any = 1;
                       acc *= base;
                       acc += c;
               }
       }
       if (any < 0) {
               acc = ULONG_MAX;
               errno = ERANGE;
       } else if (neg)
               acc = -acc;
       if (endptr != 0)
               *endptr = any ? s - 1 : nptr;
       return (acc);
}