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