1 /* $OpenBSD: strtoimax.c,v 1.1 2006/01/13 17:58:09 millert Exp $ */
2
3 /*-
4 * Copyright (c) 1992 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 <ctype.h>
33 #include <errno.h>
34 #include <inttypes.h>
35
36 /*
37 * Convert a string to an intmax_t
38 *
39 * Ignores `locale' stuff. Assumes that the upper and lower case
40 * alphabets and digits are each contiguous.
41 */
42 intmax_t
strtoimax(const char * nptr,char ** endptr,int base)43 strtoimax(const char *nptr, char **endptr, int base)
44 {
45 const char *s;
46 intmax_t 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 intmax_t is
84 * [-9223372036854775808..9223372036854775807] and the input base
85 * is 10, cutoff will be set to 922337203685477580 and cutlim to
86 * either 7 (neg==0) or 8 (neg==1), meaning that if we have
87 * accumulated a value > 922337203685477580, or equal but the
88 * next digit is > 7 (or 8), the number is too big, and we will
89 * return a range error.
90 *
91 * Set any if any `digits' consumed; make it negative to indicate
92 * overflow.
93 */
94 cutoff = neg ? INTMAX_MIN : INTMAX_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 = INTMAX_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 = INTMAX_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