1/*	$OpenBSD: strtoimax.c,v 1.2 2014/09/13 20:10:12 schwarze Exp $	*/
2/*
3 * Copyright (c) 1992 The Regents of the University of California.
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 * 3. 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 <ctype.h>
32#include <errno.h>
33#include <inttypes.h>
34
35/*
36 * Convert a string to an intmax_t
37 *
38 * Ignores `locale' stuff.  Assumes that the upper and lower case
39 * alphabets and digits are each contiguous.
40 */
41intmax_t
42strtoimax(const char *nptr, char **endptr, int base)
43{
44	const char *s;
45	intmax_t acc, cutoff;
46	int c;
47	int neg, any, cutlim;
48
49	/*
50	 * Ensure that base is between 2 and 36 inclusive, or the special
51	 * value of 0.
52	 */
53	if (base < 0 || base == 1 || base > 36) {
54		if (endptr != 0)
55			*endptr = (char *)nptr;
56		errno = EINVAL;
57		return 0;
58	}
59
60	/*
61	 * Skip white space and pick up leading +/- sign if any.
62	 * If base is 0, allow 0x for hex and 0 for octal, else
63	 * assume decimal; if base is already 16, allow 0x.
64	 */
65	s = nptr;
66	do {
67		c = (unsigned char) *s++;
68	} while (isspace(c));
69	if (c == '-') {
70		neg = 1;
71		c = *s++;
72	} else {
73		neg = 0;
74		if (c == '+')
75			c = *s++;
76	}
77	if ((base == 0 || base == 16) &&
78	    c == '0' && (*s == 'x' || *s == 'X')) {
79		c = s[1];
80		s += 2;
81		base = 16;
82	}
83	if (base == 0)
84		base = c == '0' ? 8 : 10;
85
86	/*
87	 * Compute the cutoff value between legal numbers and illegal
88	 * numbers.  That is the largest legal value, divided by the
89	 * base.  An input number that is greater than this value, if
90	 * followed by a legal input character, is too big.  One that
91	 * is equal to this value may be valid or not; the limit
92	 * between valid and invalid numbers is then based on the last
93	 * digit.  For instance, if the range for intmax_t is
94	 * [-9223372036854775808..9223372036854775807] and the input base
95	 * is 10, cutoff will be set to 922337203685477580 and cutlim to
96	 * either 7 (neg==0) or 8 (neg==1), meaning that if we have
97	 * accumulated a value > 922337203685477580, or equal but the
98	 * next digit is > 7 (or 8), the number is too big, and we will
99	 * return a range error.
100	 *
101	 * Set any if any `digits' consumed; make it negative to indicate
102	 * overflow.
103	 */
104	cutoff = neg ? INTMAX_MIN : INTMAX_MAX;
105	cutlim = cutoff % base;
106	cutoff /= base;
107	if (neg) {
108		if (cutlim > 0) {
109			cutlim -= base;
110			cutoff += 1;
111		}
112		cutlim = -cutlim;
113	}
114	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
115		if (isdigit(c))
116			c -= '0';
117		else if (isalpha(c))
118			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
119		else
120			break;
121		if (c >= base)
122			break;
123		if (any < 0)
124			continue;
125		if (neg) {
126			if (acc < cutoff || (acc == cutoff && c > cutlim)) {
127				any = -1;
128				acc = INTMAX_MIN;
129				errno = ERANGE;
130			} else {
131				any = 1;
132				acc *= base;
133				acc -= c;
134			}
135		} else {
136			if (acc > cutoff || (acc == cutoff && c > cutlim)) {
137				any = -1;
138				acc = INTMAX_MAX;
139				errno = ERANGE;
140			} else {
141				any = 1;
142				acc *= base;
143				acc += c;
144			}
145		}
146	}
147	if (endptr != 0)
148		*endptr = (char *) (any ? s - 1 : nptr);
149	return (acc);
150}
151