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 {
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