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      1 /*	$OpenBSD: strtoul.c,v 1.7 2005/08/08 08:05:37 espie Exp $ */
      2 /*
      3  * Copyright (c) 1990 Regents of the University of California.
      4  * All rights reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  * 3. Neither the name of the University nor the names of its contributors
     15  *    may be used to endorse or promote products derived from this software
     16  *    without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     28  * SUCH DAMAGE.
     29  */
     30 
     31 #include <ctype.h>
     32 #include <errno.h>
     33 #include <limits.h>
     34 #include <stdlib.h>
     35 
     36 /*
     37  * Convert a string to an unsigned long integer.
     38  *
     39  * Ignores `locale' stuff.  Assumes that the upper and lower case
     40  * alphabets and digits are each contiguous.
     41  */
     42 unsigned long
     43 strtoul(const char *nptr, char **endptr, int base)
     44 {
     45 	const char *s;
     46 	unsigned long acc, cutoff;
     47 	int c;
     48 	int neg, any, cutlim;
     49 
     50 	/*
     51 	 * See strtol for comments as to the logic used.
     52 	 */
     53 	s = nptr;
     54 	do {
     55 		c = (unsigned char) *s++;
     56 	} while (isspace(c));
     57 	if (c == '-') {
     58 		neg = 1;
     59 		c = *s++;
     60 	} else {
     61 		neg = 0;
     62 		if (c == '+')
     63 			c = *s++;
     64 	}
     65 	if ((base == 0 || base == 16) &&
     66 	    c == '0' && (*s == 'x' || *s == 'X')) {
     67 		c = s[1];
     68 		s += 2;
     69 		base = 16;
     70 	}
     71 	if (base == 0)
     72 		base = c == '0' ? 8 : 10;
     73 
     74 	cutoff = ULONG_MAX / (unsigned long)base;
     75 	cutlim = ULONG_MAX % (unsigned long)base;
     76 	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
     77 		if (isdigit(c))
     78 			c -= '0';
     79 		else if (isalpha(c))
     80 			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
     81 		else
     82 			break;
     83 		if (c >= base)
     84 			break;
     85 		if (any < 0)
     86 			continue;
     87 		if (acc > cutoff || (acc == cutoff && c > cutlim)) {
     88 			any = -1;
     89 			acc = ULONG_MAX;
     90 			errno = ERANGE;
     91 		} else {
     92 			any = 1;
     93 			acc *= (unsigned long)base;
     94 			acc += c;
     95 		}
     96 	}
     97 	if (neg && any > 0)
     98 		acc = -acc;
     99 	if (endptr != 0)
    100 		*endptr = (char *) (any ? s - 1 : nptr);
    101 	return (acc);
    102 }
    103