strtoq.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 * 4. Neither the name of the University nor the names of its contributors
19 *    may be used to endorse or promote products derived from this software
20 *    without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35#include <sys/cdefs.h>
36__FBSDID("$FreeBSD: stable/11/sys/libkern/strtoq.c 330897 2018-03-14 03:19:51Z eadler $");
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 quad integer.
45 *
46 * Ignores `locale' stuff.  Assumes that the upper and lower case
47 * alphabets and digits are each contiguous.
48 */
49quad_t
50strtoq(const char *nptr, char **endptr, int base)
51{
52	const char *s;
53	u_quad_t acc;
54	unsigned char c;
55	u_quad_t qbase, cutoff;
56	int neg, any, cutlim;
57
58	/*
59	 * Skip white space and pick up leading +/- sign if any.
60	 * If base is 0, allow 0x for hex and 0 for octal, else
61	 * assume decimal; if base is already 16, allow 0x.
62	 */
63	s = nptr;
64	do {
65		c = *s++;
66	} while (isspace(c));
67	if (c == '-') {
68		neg = 1;
69		c = *s++;
70	} else {
71		neg = 0;
72		if (c == '+')
73			c = *s++;
74	}
75	if ((base == 0 || base == 16) &&
76	    c == '0' && (*s == 'x' || *s == 'X')) {
77		c = s[1];
78		s += 2;
79		base = 16;
80	}
81	if (base == 0)
82		base = c == '0' ? 8 : 10;
83
84	/*
85	 * Compute the cutoff value between legal numbers and illegal
86	 * numbers.  That is the largest legal value, divided by the
87	 * base.  An input number that is greater than this value, if
88	 * followed by a legal input character, is too big.  One that
89	 * is equal to this value may be valid or not; the limit
90	 * between valid and invalid numbers is then based on the last
91	 * digit.  For instance, if the range for quads is
92	 * [-9223372036854775808..9223372036854775807] and the input base
93	 * is 10, cutoff will be set to 922337203685477580 and cutlim to
94	 * either 7 (neg==0) or 8 (neg==1), meaning that if we have
95	 * accumulated a value > 922337203685477580, or equal but the
96	 * next digit is > 7 (or 8), the number is too big, and we will
97	 * return a range error.
98	 *
99	 * Set any if any `digits' consumed; make it negative to indicate
100	 * overflow.
101	 */
102	qbase = (unsigned)base;
103	cutoff = neg ? (u_quad_t)-(QUAD_MIN + QUAD_MAX) + QUAD_MAX : QUAD_MAX;
104	cutlim = cutoff % qbase;
105	cutoff /= qbase;
106	for (acc = 0, any = 0;; c = *s++) {
107		if (!isascii(c))
108			break;
109		if (isdigit(c))
110			c -= '0';
111		else if (isalpha(c))
112			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
113		else
114			break;
115		if (c >= base)
116			break;
117		if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
118			any = -1;
119		else {
120			any = 1;
121			acc *= qbase;
122			acc += c;
123		}
124	}
125	if (any < 0) {
126		acc = neg ? QUAD_MIN : QUAD_MAX;
127	} else if (neg)
128		acc = -acc;
129	if (endptr != NULL)
130		*endptr = __DECONST(char *, any ? s - 1 : nptr);
131	return (acc);
132}
133