strtol.c revision 101912 
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#if defined(LIBC_SCCS) && !defined(lint)
35static char sccsid[] = "@(#)strtol.c	8.1 (Berkeley) 6/4/93";
36#endif /* LIBC_SCCS and not lint */
37#include <sys/cdefs.h>
38__FBSDID("$FreeBSD: head/lib/libc/stdlib/strtol.c 101912 2002-08-15 09:25:04Z robert $");
39
40#include <limits.h>
41#include <ctype.h>
42#include <errno.h>
43#include <stdlib.h>
44
45
46/*
47 * Convert a string to a long integer.
48 *
49 * Assumes that the upper and lower case
50 * alphabets and digits are each contiguous.
51 */
52long
53strtol(const char *__restrict nptr, char **__restrict endptr, int base)
54{
55	const char *s;
56	unsigned long acc;
57	char c;
58	unsigned long cutoff;
59	int neg, 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	s = nptr;
67	do {
68		c = *s++;
69	} while (isspace((unsigned char)c));
70	if (c == '-') {
71		neg = 1;
72		c = *s++;
73	} else {
74		neg = 0;
75		if (c == '+')
76			c = *s++;
77	}
78	if ((base == 0 || base == 16) &&
79	    c == '0' && (*s == 'x' || *s == 'X')) {
80		c = s[1];
81		s += 2;
82		base = 16;
83	}
84	if (base == 0)
85		base = c == '0' ? 8 : 10;
86	acc = any = 0;
87	if (base < 2 || base > 36)
88		goto noconv;
89
90	/*
91	 * Compute the cutoff value between legal numbers and illegal
92	 * numbers.  That is the largest legal value, divided by the
93	 * base.  An input number that is greater than this value, if
94	 * followed by a legal input character, is too big.  One that
95	 * is equal to this value may be valid or not; the limit
96	 * between valid and invalid numbers is then based on the last
97	 * digit.  For instance, if the range for longs is
98	 * [-2147483648..2147483647] and the input base is 10,
99	 * cutoff will be set to 214748364 and cutlim to either
100	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
101	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
102	 * the number is too big, and we will return a range error.
103	 *
104	 * Set 'any' if any `digits' consumed; make it negative to indicate
105	 * overflow.
106	 */
107	cutoff = neg ? (unsigned long)-(LONG_MIN + LONG_MAX) + LONG_MAX
108	    : LONG_MAX;
109	cutlim = cutoff % base;
110	cutoff /= base;
111	for ( ; ; c = *s++) {
112		if (c >= '0' && c <= '9')
113			c -= '0';
114		else if (c >= 'A' && c <= 'Z')
115			c -= 'A' - 10;
116		else if (c >= 'a' && c <= 'z')
117			c -= 'a' - 10;
118		else
119			break;
120		if (c >= base)
121			break;
122		if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
123			any = -1;
124		else {
125			any = 1;
126			acc *= base;
127			acc += c;
128		}
129	}
130	if (any < 0) {
131		acc = neg ? LONG_MIN : LONG_MAX;
132		errno = ERANGE;
133	} else if (!any) {
134noconv:
135		errno = EINVAL;
136	} else if (neg)
137		acc = -acc;
138	if (endptr != NULL)
139		*endptr = (char *)(any ? s - 1 : nptr);
140	return (acc);
141}
142