1/*	$OpenBSD: strtol.c,v 1.7 2005/08/08 08:05:37 espie Exp $ */
2/*-
3 * Copyright (c) 1990 The 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/*
38 * Convert a string to a long integer.
39 *
40 * Ignores `locale' stuff.  Assumes that the upper and lower case
41 * alphabets and digits are each contiguous.
42 */
43long
44strtol(const char *nptr, char **endptr, int base)
45{
46	const char *s;
47	long acc, cutoff;
48	int c;
49	int neg, any, cutlim;
50
51	/*
52	 * Skip white space and pick up leading +/- sign if any.
53	 * If base is 0, allow 0x for hex and 0 for octal, else
54	 * assume decimal; if base is already 16, allow 0x.
55	 */
56	s = nptr;
57	do {
58		c = (unsigned char) *s++;
59	} while (isspace(c));
60	if (c == '-') {
61		neg = 1;
62		c = *s++;
63	} else {
64		neg = 0;
65		if (c == '+')
66			c = *s++;
67	}
68	if ((base == 0 || base == 16) &&
69	    c == '0' && (*s == 'x' || *s == 'X')) {
70		c = s[1];
71		s += 2;
72		base = 16;
73	}
74	if (base == 0)
75		base = c == '0' ? 8 : 10;
76
77	/*
78	 * Compute the cutoff value between legal numbers and illegal
79	 * numbers.  That is the largest legal value, divided by the
80	 * base.  An input number that is greater than this value, if
81	 * followed by a legal input character, is too big.  One that
82	 * is equal to this value may be valid or not; the limit
83	 * between valid and invalid numbers is then based on the last
84	 * digit.  For instance, if the range for longs is
85	 * [-2147483648..2147483647] and the input base is 10,
86	 * cutoff will be set to 214748364 and cutlim to either
87	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
88	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
89	 * the number is too big, and we will return a range error.
90	 *
91	 * Set any if any `digits' consumed; make it negative to indicate
92	 * overflow.
93	 */
94	cutoff = neg ? LONG_MIN : LONG_MAX;
95	cutlim = cutoff % base;
96	cutoff /= base;
97	if (neg) {
98		if (cutlim > 0) {
99			cutlim -= base;
100			cutoff += 1;
101		}
102		cutlim = -cutlim;
103	}
104	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
105		if (isdigit(c))
106			c -= '0';
107		else if (isalpha(c))
108			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
109		else
110			break;
111		if (c >= base)
112			break;
113		if (any < 0)
114			continue;
115		if (neg) {
116			if (acc < cutoff || (acc == cutoff && c > cutlim)) {
117				any = -1;
118				acc = LONG_MIN;
119				errno = ERANGE;
120			} else {
121				any = 1;
122				acc *= base;
123				acc -= c;
124			}
125		} else {
126			if (acc > cutoff || (acc == cutoff && c > cutlim)) {
127				any = -1;
128				acc = LONG_MAX;
129				errno = ERANGE;
130			} else {
131				any = 1;
132				acc *= base;
133				acc += c;
134			}
135		}
136	}
137	if (endptr != 0)
138		*endptr = (char *) (any ? s - 1 : nptr);
139	return (acc);
140}
141