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strtol.c (4415B)
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1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #include <limits.h>
35 #include <ctype.h>
36 #include <errno.h>
37 #include <stdlib.h>
38
39
40 /*
41 * Convert a string to a long integer.
42 *
43 * Assumes that the upper and lower case
44 * alphabets and digits are each contiguous.
45 */
46 long
47 strtol(const char * __restrict nptr, char ** __restrict endptr, int base)
48 {
49 const char *s;
50 unsigned long acc;
51 char c;
52 unsigned long cutoff;
53 int neg, any, cutlim;
54
55 /*
56 * Skip white space and pick up leading +/- sign if any.
57 * If base is 0, allow 0x for hex and 0 for octal, else
58 * assume decimal; if base is already 16, allow 0x.
59 */
60 s = nptr;
61 do {
62 c = *s++;
63 } while (isspace((unsigned char)c));
64 if (c == '-') {
65 neg = 1;
66 c = *s++;
67 } else {
68 neg = 0;
69 if (c == '+')
70 c = *s++;
71 }
72 if ((base == 0 || base == 16) &&
73 c == '0' && (*s == 'x' || *s == 'X') &&
74 ((s[1] >= '0' && s[1] <= '9') ||
75 (s[1] >= 'A' && s[1] <= 'F') ||
76 (s[1] >= 'a' && s[1] <= 'f'))) {
77 c = s[1];
78 s += 2;
79 base = 16;
80 }
81 if (base == 0)
82 base = c == '0' ? 8 : 10;
83 acc = any = 0;
84 if (base < 2 || base > 36)
85 goto noconv;
86
87 /*
88 * Compute the cutoff value between legal numbers and illegal
89 * numbers. That is the largest legal value, divided by the
90 * base. An input number that is greater than this value, if
91 * followed by a legal input character, is too big. One that
92 * is equal to this value may be valid or not; the limit
93 * between valid and invalid numbers is then based on the last
94 * digit. For instance, if the range for longs is
95 * [-2147483648..2147483647] and the input base is 10,
96 * cutoff will be set to 214748364 and cutlim to either
97 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
98 * a value > 214748364, or equal but the next digit is > 7 (or 8),
99 * the number is too big, and we will return a range error.
100 *
101 * Set 'any' if any `digits' consumed; make it negative to indicate
102 * overflow.
103 */
104 cutoff = neg ? (unsigned long)-(LONG_MIN + LONG_MAX) + LONG_MAX
105 : LONG_MAX;
106 cutlim = cutoff % base;
107 cutoff /= base;
108 for ( ; ; c = *s++) {
109 if (c >= '0' && c <= '9')
110 c -= '0';
111 else if (c >= 'A' && c <= 'Z')
112 c -= 'A' - 10;
113 else if (c >= 'a' && c <= 'z')
114 c -= 'a' - 10;
115 else
116 break;
117 if (c >= base)
118 break;
119 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
120 any = -1;
121 else {
122 any = 1;
123 acc *= base;
124 acc += c;
125 }
126 }
127 if (any < 0) {
128 acc = neg ? LONG_MIN : LONG_MAX;
129 errno = ERANGE;
130 } else if (!any) {
131 noconv:
132 errno = EINVAL;
133 } else if (neg)
134 acc = -acc;
135 if (endptr != NULL)
136 *endptr = (char *)(any ? s - 1 : nptr);
137 return (acc);
138 }