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strtol.c revision 1.17 
      1 /*	$NetBSD: strtol.c,v 1.17 2005/11/29 03:12:00 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  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/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 #if 0
     35 static char sccsid[] = "@(#)strtol.c	8.1 (Berkeley) 6/4/93";
     36 #else
     37 __RCSID("$NetBSD: strtol.c,v 1.17 2005/11/29 03:12:00 christos Exp $");
     38 #endif
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include <assert.h>
     42 #include <ctype.h>
     43 #include <errno.h>
     44 #include <limits.h>
     45 #include <stdlib.h>
     46 
     47 
     48 /*
     49  * Convert a string to a long integer.
     50  *
     51  * Ignores `locale' stuff.  Assumes that the upper and lower case
     52  * alphabets and digits are each contiguous.
     53  */
     54 long
     55 strtol(nptr, endptr, base)
     56 	const char *nptr;
     57 	char **endptr;
     58 	int base;
     59 {
     60 	const char *s;
     61 	long acc, cutoff;
     62 	int c;
     63 	int neg, any, cutlim;
     64 
     65 	_DIAGASSERT(nptr != NULL);
     66 	/* endptr may be NULL */
     67 
     68 	/*
     69 	 * Skip white space and pick up leading +/- sign if any.
     70 	 * If base is 0, allow 0x for hex and 0 for octal, else
     71 	 * assume decimal; if base is already 16, allow 0x.
     72 	 */
     73 	s = nptr;
     74 	do {
     75 		c = (unsigned char) *s++;
     76 	} while (isspace(c));
     77 	if (c == '-') {
     78 		neg = 1;
     79 		c = *s++;
     80 	} else {
     81 		neg = 0;
     82 		if (c == '+')
     83 			c = *s++;
     84 	}
     85 	if ((base == 0 || base == 16) &&
     86 	    c == '0' && (*s == 'x' || *s == 'X')) {
     87 		c = s[1];
     88 		s += 2;
     89 		base = 16;
     90 	}
     91 	if (base == 0)
     92 		base = c == '0' ? 8 : 10;
     93 
     94 	/*
     95 	 * Compute the cutoff value between legal numbers and illegal
     96 	 * numbers.  That is the largest legal value, divided by the
     97 	 * base.  An input number that is greater than this value, if
     98 	 * followed by a legal input character, is too big.  One that
     99 	 * is equal to this value may be valid or not; the limit
    100 	 * between valid and invalid numbers is then based on the last
    101 	 * digit.  For instance, if the range for longs is
    102 	 * [-2147483648..2147483647] and the input base is 10,
    103 	 * cutoff will be set to 214748364 and cutlim to either
    104 	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
    105 	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
    106 	 * the number is too big, and we will return a range error.
    107 	 *
    108 	 * Set any if any `digits' consumed; make it negative to indicate
    109 	 * overflow.
    110 	 */
    111 	cutoff = neg ? LONG_MIN : LONG_MAX;
    112 	cutlim = (int)(cutoff % base);
    113 	cutoff /= base;
    114 	if (neg) {
    115 		if (cutlim > 0) {
    116 			cutlim -= base;
    117 			cutoff += 1;
    118 		}
    119 		cutlim = -cutlim;
    120 	}
    121 	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
    122 		if (isdigit(c))
    123 			c -= '0';
    124 		else if (isalpha(c))
    125 			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
    126 		else
    127 			break;
    128 		if (c >= base)
    129 			break;
    130 		if (any < 0)
    131 			continue;
    132 		if (neg) {
    133 			if (acc < cutoff || (acc == cutoff && c > cutlim)) {
    134 				any = -1;
    135 				acc = LONG_MIN;
    136 				errno = ERANGE;
    137 			} else {
    138 				any = 1;
    139 				acc *= base;
    140 				acc -= c;
    141 			}
    142 		} else {
    143 			if (acc > cutoff || (acc == cutoff && c > cutlim)) {
    144 				any = -1;
    145 				acc = LONG_MAX;
    146 				errno = ERANGE;
    147 			} else {
    148 				any = 1;
    149 				acc *= base;
    150 				acc += c;
    151 			}
    152 		}
    153 	}
    154 	if (endptr != 0)
    155 		*endptr = __UNCONST(any ? s - 1 : nptr);
    156 	return (acc);
    157 }
    158