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      1 /*	$OpenBSD: strtol.c,v 1.9 2013/04/17 17:40:35 tedu 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 	 * Ensure that base is between 2 and 36 inclusive, or the special
     53 	 * value of 0.
     54 	 */
     55 	if (base != 0 && (base < 2 || base > 36)) {
     56 		if (endptr != 0)
     57 			*endptr = (char *)nptr;
     58 		errno = EINVAL;
     59 		return 0;
     60 	}
     61 
     62 	/*
     63 	 * Skip white space and pick up leading +/- sign if any.
     64 	 * If base is 0, allow 0x for hex and 0 for octal, else
     65 	 * assume decimal; if base is already 16, allow 0x.
     66 	 */
     67 	s = nptr;
     68 	do {
     69 		c = (unsigned char) *s++;
     70 	} while (isspace(c));
     71 	if (c == '-') {
     72 		neg = 1;
     73 		c = *s++;
     74 	} else {
     75 		neg = 0;
     76 		if (c == '+')
     77 			c = *s++;
     78 	}
     79 	if ((base == 0 || base == 16) &&
     80 	    c == '0' && (*s == 'x' || *s == 'X')) {
     81 		c = s[1];
     82 		s += 2;
     83 		base = 16;
     84 	}
     85 	if (base == 0)
     86 		base = c == '0' ? 8 : 10;
     87 
     88 	/*
     89 	 * Compute the cutoff value between legal numbers and illegal
     90 	 * numbers.  That is the largest legal value, divided by the
     91 	 * base.  An input number that is greater than this value, if
     92 	 * followed by a legal input character, is too big.  One that
     93 	 * is equal to this value may be valid or not; the limit
     94 	 * between valid and invalid numbers is then based on the last
     95 	 * digit.  For instance, if the range for longs is
     96 	 * [-2147483648..2147483647] and the input base is 10,
     97 	 * cutoff will be set to 214748364 and cutlim to either
     98 	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
     99 	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
    100 	 * the number is too big, and we will return a range error.
    101 	 *
    102 	 * Set any if any `digits' consumed; make it negative to indicate
    103 	 * overflow.
    104 	 */
    105 	cutoff = neg ? LONG_MIN : LONG_MAX;
    106 	cutlim = cutoff % base;
    107 	cutoff /= base;
    108 	if (neg) {
    109 		if (cutlim > 0) {
    110 			cutlim -= base;
    111 			cutoff += 1;
    112 		}
    113 		cutlim = -cutlim;
    114 	}
    115 	for (acc = 0, any = 0;; c = (unsigned char) *s++) {
    116 		if (isdigit(c))
    117 			c -= '0';
    118 		else if (isalpha(c))
    119 			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
    120 		else
    121 			break;
    122 		if (c >= base)
    123 			break;
    124 		if (any < 0)
    125 			continue;
    126 		if (neg) {
    127 			if (acc < cutoff || (acc == cutoff && c > cutlim)) {
    128 				any = -1;
    129 				acc = LONG_MIN;
    130 				errno = ERANGE;
    131 			} else {
    132 				any = 1;
    133 				acc *= base;
    134 				acc -= c;
    135 			}
    136 		} else {
    137 			if (acc > cutoff || (acc == cutoff && c > cutlim)) {
    138 				any = -1;
    139 				acc = LONG_MAX;
    140 				errno = ERANGE;
    141 			} else {
    142 				any = 1;
    143 				acc *= base;
    144 				acc += c;
    145 			}
    146 		}
    147 	}
    148 	if (endptr != 0)
    149 		*endptr = (char *) (any ? s - 1 : nptr);
    150 	return (acc);
    151 }
    152