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
95 /* BIONIC: avoid division and module for common cases */
96 #define CASE_BASE(x) \
97 case x: \
98 if (neg) { \
99 cutlim = INTMAX_MIN % x; \
100 cutoff = INTMAX_MIN / x; \
101 } else { \
102 cutlim = INTMAX_MAX % x; \
103 cutoff = INTMAX_MAX / x; \
104 }; \
105 break
106
107 switch (base) {
108 case 4:
109 if (neg) {
110 cutlim = (int)(INTMAX_MIN % 4);
111 cutoff = INTMAX_MIN / 4;
112 } else {
113 cutlim = (int)(INTMAX_MAX % 4);
114 cutoff = INTMAX_MAX / 4;
115 }
116 break;
117
118 CASE_BASE(8);
119 CASE_BASE(10);
120 CASE_BASE(16);
121 default:
122 cutoff = neg ? INTMAX_MIN : INTMAX_MAX;
123 cutlim = cutoff % base;
124 cutoff /= base;
125 }
126 #undef CASE_BASE
127
128 if (neg) {
129 if (cutlim > 0) {
130 cutlim -= base;
131 cutoff += 1;
132 }
133 cutlim = -cutlim;
134 }
135 for (acc = 0, any = 0;; c = (unsigned char) *s++) {
136 if (isdigit(c))
137 c -= '0';
138 else if (isalpha(c))
139 c -= isupper(c) ? 'A' - 10 : 'a' - 10;
140 else
141 break;
142 if (c >= base)
143 break;
144 if (any < 0)
145 continue;
146 if (neg) {
147 if (acc < cutoff || (acc == cutoff && c > cutlim)) {
148 any = -1;
149 acc = INTMAX_MIN;
150 errno = ERANGE;
151 } else {
152 any = 1;
153 acc *= base;
154 acc -= c;
155 }
156 } else {
157 if (acc > cutoff || (acc == cutoff && c > cutlim)) {
158 any = -1;
159 acc = INTMAX_MAX;
160 errno = ERANGE;
161 } else {
162 any = 1;
163 acc *= base;
164 acc += c;
165 }
166 }
167 }
168 if (endptr != 0)
169 *endptr = (char *) (any ? s - 1 : nptr);
170 return (acc);
171 }
172