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