strtol.c revision 1.2 
1/*-
2 * Copyright (c) 1990 The Regents of the University of California.
3 * 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. [rescinded 22 July 1999]
14 * 4. Neither the name of the University nor the names of its contributors
15 *    may be used to endorse or promote products derived from this software
16 *    without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31#include <limits.h>
32#include <ctype.h>
33#include <errno.h>
34#if 0
35#include <stdlib.h>
36#endif
37#include "ansidecl.h"
38
39/* FIXME: It'd be nice to configure around these, but the include files are too
40   painful.  These macros should at least be more portable than hardwired hex
41   constants. */
42
43#ifndef ULONG_MAX
44#define	ULONG_MAX	((unsigned long)(~0L))		/* 0xFFFFFFFF */
45#endif
46
47#ifndef LONG_MAX
48#define	LONG_MAX	((long)(ULONG_MAX >> 1))	/* 0x7FFFFFFF */
49#endif
50
51#ifndef LONG_MIN
52#define	LONG_MIN	((long)(~LONG_MAX))		/* 0x80000000 */
53#endif
54
55/*
56 * Convert a string to a long integer.
57 *
58 * Ignores `locale' stuff.  Assumes that the upper and lower case
59 * alphabets and digits are each contiguous.
60 */
61long
62strtol(nptr, endptr, base)
63	const char *nptr;
64	char **endptr;
65	register int base;
66{
67	register const char *s = nptr;
68	register unsigned long acc;
69	register int c;
70	register unsigned long cutoff;
71	register int neg = 0, any, cutlim;
72
73	/*
74	 * Skip white space and pick up leading +/- sign if any.
75	 * If base is 0, allow 0x for hex and 0 for octal, else
76	 * assume decimal; if base is already 16, allow 0x.
77	 */
78	do {
79		c = *s++;
80	} while (isspace(c));
81	if (c == '-') {
82		neg = 1;
83		c = *s++;
84	} else if (c == '+')
85		c = *s++;
86	if ((base == 0 || base == 16) &&
87	    c == '0' && (*s == 'x' || *s == 'X')) {
88		c = s[1];
89		s += 2;
90		base = 16;
91	}
92	if (base == 0)
93		base = c == '0' ? 8 : 10;
94
95	/*
96	 * Compute the cutoff value between legal numbers and illegal
97	 * numbers.  That is the largest legal value, divided by the
98	 * base.  An input number that is greater than this value, if
99	 * followed by a legal input character, is too big.  One that
100	 * is equal to this value may be valid or not; the limit
101	 * between valid and invalid numbers is then based on the last
102	 * digit.  For instance, if the range for longs is
103	 * [-2147483648..2147483647] and the input base is 10,
104	 * cutoff will be set to 214748364 and cutlim to either
105	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
106	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
107	 * the number is too big, and we will return a range error.
108	 *
109	 * Set any if any `digits' consumed; make it negative to indicate
110	 * overflow.
111	 */
112	cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
113	cutlim = cutoff % (unsigned long)base;
114	cutoff /= (unsigned long)base;
115	for (acc = 0, any = 0;; c = *s++) {
116		if (isdigit(c))
117			c -= '0';
118		else if (isalpha(c))
119			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
120		else
121			break;
122		if (c >= base)
123			break;
124		if (any < 0 || acc > cutoff || acc == cutoff && c > cutlim)
125			any = -1;
126		else {
127			any = 1;
128			acc *= base;
129			acc += c;
130		}
131	}
132	if (any < 0) {
133		acc = neg ? LONG_MIN : LONG_MAX;
134		errno = ERANGE;
135	} else if (neg)
136		acc = -acc;
137	if (endptr != 0)
138		*endptr = (char *) (any ? s - 1 : nptr);
139	return (acc);
140}
141