1/* $OpenBSD: strtol.c,v 1.4 2022/01/08 06:49:41 guenther Exp $ */
2
3/*-
4 * Copyright (c) 1990 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 <sys/types.h>
33#include <limits.h>
34
35#include "util.h"
36
37/*
38 * Convert a string to a long integer.
39 *
40 * Ignores `locale' stuff.  Assumes that the upper and lower case
41 * alphabets and digits are each contiguous.
42 */
43long
44_dl_strtol(const char *nptr, char **endptr, int base)
45{
46	const char *s;
47	long acc, cutoff;
48	int c;
49	int neg, any, cutlim;
50
51	/*
52	 * Skip white space and pick up leading +/- sign if any.
53	 * If base is 0, allow 0x for hex and 0 for octal, else
54	 * assume decimal; if base is already 16, allow 0x.
55	 */
56	s = nptr;
57	do {
58		c = (unsigned char) *s++;
59	} while (c <= ' ' || c >= 0x7f);
60	if (c == '-') {
61		neg = 1;
62		c = *s++;
63	} else {
64		neg = 0;
65		if (c == '+')
66			c = *s++;
67	}
68	if ((base == 0 || base == 16) && c == '0' &&
69	    (*s == 'x' || *s == 'X') && ((s[1] >= '0' && s[1] <= '9') ||
70	    (s[1] >= 'A' && s[1] <= 'F') || (s[1] >= 'a' && s[1] <= 'f'))) {
71		c = s[1];
72		s += 2;
73		base = 16;
74	}
75	if (base == 0)
76		base = c == '0' ? 8 : 10;
77
78	/*
79	 * Compute the cutoff value between legal numbers and illegal
80	 * numbers.  That is the largest legal value, divided by the
81	 * base.  An input number that is greater than this value, if
82	 * followed by a legal input character, is too big.  One that
83	 * is equal to this value may be valid or not; the limit
84	 * between valid and invalid numbers is then based on the last
85	 * digit.  For instance, if the range for longs is
86	 * [-2147483648..2147483647] and the input base is 10,
87	 * cutoff will be set to 214748364 and cutlim to either
88	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
89	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
90	 * the number is too big, and we will return a range error.
91	 *
92	 * Set any if any `digits' consumed; make it negative to indicate
93	 * overflow.
94	 */
95	cutoff = neg ? LONG_MIN : LONG_MAX;
96	cutlim = cutoff % base;
97	cutoff /= base;
98	if (neg) {
99		if (cutlim > 0) {
100			cutlim -= base;
101			cutoff += 1;
102		}
103		cutlim = -cutlim;
104	}
105	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
106		if (c >= '0' && c <= '9')
107			c -= '0';
108		else if (c >= 'A' && c <= 'Z')
109			c -= 'A' - 10;
110		else if (c >= 'a' && c <= 'z')
111			c -= 'a' - 10;
112		else
113			break;
114		if (c >= base)
115			break;
116		if (any < 0)
117			continue;
118		if (neg) {
119			if (acc < cutoff || (acc == cutoff && c > cutlim)) {
120				any = -1;
121				acc = LONG_MIN;
122			} else {
123				any = 1;
124				acc *= base;
125				acc -= c;
126			}
127		} else {
128			if (acc > cutoff || (acc == cutoff && c > cutlim)) {
129				any = -1;
130				acc = LONG_MAX;
131			} else {
132				any = 1;
133				acc *= base;
134				acc += c;
135			}
136		}
137	}
138	if (endptr != 0)
139		*endptr = (char *) (any ? s - 1 : nptr);
140	return (acc);
141}
142