xref: /freebsd/sys/libkern/strtol.c (revision ef36b3f75658d201edb495068db5e1be49593de5)
1 /*-
2  * Copyright (c) 1990, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software contributed to Berkeley by
6  * Chris Torek.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. Neither the name of the University nor the names of its contributors
17  *    may be used to endorse or promote products derived from this software
18  *    without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30  * SUCH DAMAGE.
31  *
32  * From: @(#)strtol.c	8.1 (Berkeley) 6/4/93
33  */
34 
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
37 
38 #include <sys/param.h>
39 #include <sys/systm.h>
40 #include <sys/ctype.h>
41 #include <sys/limits.h>
42 
43 /*
44  * Convert a string to a long integer.
45  *
46  * Ignores `locale' stuff.  Assumes that the upper and lower case
47  * alphabets and digits are each contiguous.
48  */
49 long
50 strtol(nptr, endptr, base)
51 	const char *nptr;
52 	char **endptr;
53 	int base;
54 {
55 	const char *s = nptr;
56 	unsigned long acc;
57 	unsigned char c;
58 	unsigned long cutoff;
59 	int neg = 0, any, cutlim;
60 
61 	/*
62 	 * Skip white space and pick up leading +/- sign if any.
63 	 * If base is 0, allow 0x for hex and 0 for octal, else
64 	 * assume decimal; if base is already 16, allow 0x.
65 	 */
66 	do {
67 		c = *s++;
68 	} while (isspace(c));
69 	if (c == '-') {
70 		neg = 1;
71 		c = *s++;
72 	} else if (c == '+')
73 		c = *s++;
74 	if ((base == 0 || base == 16) &&
75 	    c == '0' && (*s == 'x' || *s == 'X')) {
76 		c = s[1];
77 		s += 2;
78 		base = 16;
79 	}
80 	if (base == 0)
81 		base = c == '0' ? 8 : 10;
82 
83 	/*
84 	 * Compute the cutoff value between legal numbers and illegal
85 	 * numbers.  That is the largest legal value, divided by the
86 	 * base.  An input number that is greater than this value, if
87 	 * followed by a legal input character, is too big.  One that
88 	 * is equal to this value may be valid or not; the limit
89 	 * between valid and invalid numbers is then based on the last
90 	 * digit.  For instance, if the range for longs is
91 	 * [-2147483648..2147483647] and the input base is 10,
92 	 * cutoff will be set to 214748364 and cutlim to either
93 	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
94 	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
95 	 * the number is too big, and we will return a range error.
96 	 *
97 	 * Set any if any `digits' consumed; make it negative to indicate
98 	 * overflow.
99 	 */
100 	cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
101 	cutlim = cutoff % (unsigned long)base;
102 	cutoff /= (unsigned long)base;
103 	for (acc = 0, any = 0;; c = *s++) {
104 		if (!isascii(c))
105 			break;
106 		if (isdigit(c))
107 			c -= '0';
108 		else if (isalpha(c))
109 			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
110 		else
111 			break;
112 		if (c >= base)
113 			break;
114 		if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
115 			any = -1;
116 		else {
117 			any = 1;
118 			acc *= base;
119 			acc += c;
120 		}
121 	}
122 	if (any < 0) {
123 		acc = neg ? LONG_MIN : LONG_MAX;
124 	} else if (neg)
125 		acc = -acc;
126 	if (endptr != NULL)
127 		*endptr = __DECONST(char *, any ? s - 1 : nptr);
128 	return (acc);
129 }
130