1 /* $OpenBSD: strtol.c,v 1.4 2022/01/08 06:49:41 guenther Exp $ */
2
3 /*-
4 * Copyright (c) 1990 The Regents of the University of California.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <sys/types.h>
33 #include <limits.h>
34
35 #include "util.h"
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
_dl_strtol(const char * nptr,char ** endptr,int base)44 _dl_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 (c <= ' ' || c >= 0x7f);
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) && c == '0' &&
69 (*s == 'x' || *s == 'X') && ((s[1] >= '0' && s[1] <= '9') ||
70 (s[1] >= 'A' && s[1] <= 'F') || (s[1] >= 'a' && s[1] <= 'f'))) {
71 c = s[1];
72 s += 2;
73 base = 16;
74 }
75 if (base == 0)
76 base = c == '0' ? 8 : 10;
77
78 /*
79 * Compute the cutoff value between legal numbers and illegal
80 * numbers. That is the largest legal value, divided by the
81 * base. An input number that is greater than this value, if
82 * followed by a legal input character, is too big. One that
83 * is equal to this value may be valid or not; the limit
84 * between valid and invalid numbers is then based on the last
85 * digit. For instance, if the range for longs is
86 * [-2147483648..2147483647] and the input base is 10,
87 * cutoff will be set to 214748364 and cutlim to either
88 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
89 * a value > 214748364, or equal but the next digit is > 7 (or 8),
90 * the number is too big, and we will return a range error.
91 *
92 * Set any if any `digits' consumed; make it negative to indicate
93 * overflow.
94 */
95 cutoff = neg ? LONG_MIN : LONG_MAX;
96 cutlim = cutoff % base;
97 cutoff /= base;
98 if (neg) {
99 if (cutlim > 0) {
100 cutlim -= base;
101 cutoff += 1;
102 }
103 cutlim = -cutlim;
104 }
105 for (acc = 0, any = 0;; c = (unsigned char) *s++) {
106 if (c >= '0' && c <= '9')
107 c -= '0';
108 else if (c >= 'A' && c <= 'Z')
109 c -= 'A' - 10;
110 else if (c >= 'a' && c <= 'z')
111 c -= 'a' - 10;
112 else
113 break;
114 if (c >= base)
115 break;
116 if (any < 0)
117 continue;
118 if (neg) {
119 if (acc < cutoff || (acc == cutoff && c > cutlim)) {
120 any = -1;
121 acc = LONG_MIN;
122 } else {
123 any = 1;
124 acc *= base;
125 acc -= c;
126 }
127 } else {
128 if (acc > cutoff || (acc == cutoff && c > cutlim)) {
129 any = -1;
130 acc = LONG_MAX;
131 } else {
132 any = 1;
133 acc *= base;
134 acc += c;
135 }
136 }
137 }
138 if (endptr != 0)
139 *endptr = (char *) (any ? s - 1 : nptr);
140 return (acc);
141 }
142