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      1 /*	$OpenBSD: strtol.c,v 1.7 2005/08/08 08:05:37 espie Exp $ */
      2 /*-
      3  * Copyright (c) 1990 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 <limits.h>
     34 #include <stdlib.h>
     35 
     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  */
     43 long
     44 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 (isspace(c));
     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) &&
     69 	    c == '0' && (*s == 'x' || *s == 'X')) {
     70 		c = s[1];
     71 		s += 2;
     72 		base = 16;
     73 	}
     74 	if (base == 0)
     75 		base = c == '0' ? 8 : 10;
     76 
     77 	/*
     78 	 * Compute the cutoff value between legal numbers and illegal
     79 	 * numbers.  That is the largest legal value, divided by the
     80 	 * base.  An input number that is greater than this value, if
     81 	 * followed by a legal input character, is too big.  One that
     82 	 * is equal to this value may be valid or not; the limit
     83 	 * between valid and invalid numbers is then based on the last
     84 	 * digit.  For instance, if the range for longs is
     85 	 * [-2147483648..2147483647] and the input base is 10,
     86 	 * cutoff will be set to 214748364 and cutlim to either
     87 	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
     88 	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
     89 	 * the number is too big, and we will return a range error.
     90 	 *
     91 	 * Set any if any `digits' consumed; make it negative to indicate
     92 	 * overflow.
     93 	 */
     94 	cutoff = neg ? LONG_MIN : LONG_MAX;
     95 	cutlim = cutoff % base;
     96 	cutoff /= base;
     97 	if (neg) {
     98 		if (cutlim > 0) {
     99 			cutlim -= base;
    100 			cutoff += 1;
    101 		}
    102 		cutlim = -cutlim;
    103 	}
    104 	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
    105 		if (isdigit(c))
    106 			c -= '0';
    107 		else if (isalpha(c))
    108 			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
    109 		else
    110 			break;
    111 		if (c >= base)
    112 			break;
    113 		if (any < 0)
    114 			continue;
    115 		if (neg) {
    116 			if (acc < cutoff || (acc == cutoff && c > cutlim)) {
    117 				any = -1;
    118 				acc = LONG_MIN;
    119 				errno = ERANGE;
    120 			} else {
    121 				any = 1;
    122 				acc *= base;
    123 				acc -= c;
    124 			}
    125 		} else {
    126 			if (acc > cutoff || (acc == cutoff && c > cutlim)) {
    127 				any = -1;
    128 				acc = LONG_MAX;
    129 				errno = ERANGE;
    130 			} else {
    131 				any = 1;
    132 				acc *= base;
    133 				acc += c;
    134 			}
    135 		}
    136 	}
    137 	if (endptr != 0)
    138 		*endptr = (char *) (any ? s - 1 : nptr);
    139 	return (acc);
    140 }
    141