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strtol.c revision 1.5 
      1 /*-
      2  * Copyright (c) 1990 The Regents of the University of California.
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #if defined(LIBC_SCCS) && !defined(lint)
     35 /*static char *sccsid = "from: @(#)strtol.c	5.4 (Berkeley) 2/23/91";*/
     36 static char *rcsid = "$Id: strtol.c,v 1.5 1995/12/20 23:14:48 mycroft Exp $";
     37 #endif /* LIBC_SCCS and not lint */
     38 
     39 #include <ctype.h>
     40 #include <errno.h>
     41 #include <limits.h>
     42 #include <stdlib.h>
     43 
     44 
     45 /*
     46  * Convert a string to a long integer.
     47  *
     48  * Ignores `locale' stuff.  Assumes that the upper and lower case
     49  * alphabets and digits are each contiguous.
     50  */
     51 long
     52 strtol(nptr, endptr, base)
     53 	const char *nptr;
     54 	char **endptr;
     55 	register int base;
     56 {
     57 	register const char *s;
     58 	register unsigned long acc;
     59 	register int c;
     60 	register unsigned long cutoff;
     61 	register int neg, any, cutlim;
     62 
     63 	/*
     64 	 * Skip white space and pick up leading +/- sign if any.
     65 	 * If base is 0, allow 0x for hex and 0 for octal, else
     66 	 * assume decimal; if base is already 16, allow 0x.
     67 	 */
     68 	s = nptr;
     69 	do {
     70 		c = *s++;
     71 	} while (isspace(c));
     72 	if (c == '-') {
     73 		neg = 1;
     74 		c = *s++;
     75 	} else {
     76 		neg = 0;
     77 		if (c == '+')
     78 			c = *s++;
     79 	}
     80 	if ((base == 0 || base == 16) &&
     81 	    c == '0' && (*s == 'x' || *s == 'X')) {
     82 		c = s[1];
     83 		s += 2;
     84 		base = 16;
     85 	}
     86 	if (base == 0)
     87 		base = c == '0' ? 8 : 10;
     88 
     89 	/*
     90 	 * Compute the cutoff value between legal numbers and illegal
     91 	 * numbers.  That is the largest legal value, divided by the
     92 	 * base.  An input number that is greater than this value, if
     93 	 * followed by a legal input character, is too big.  One that
     94 	 * is equal to this value may be valid or not; the limit
     95 	 * between valid and invalid numbers is then based on the last
     96 	 * digit.  For instance, if the range for longs is
     97 	 * [-2147483648..2147483647] and the input base is 10,
     98 	 * cutoff will be set to 214748364 and cutlim to either
     99 	 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
    100 	 * a value > 214748364, or equal but the next digit is > 7 (or 8),
    101 	 * the number is too big, and we will return a range error.
    102 	 *
    103 	 * Set any if any `digits' consumed; make it negative to indicate
    104 	 * overflow.
    105 	 */
    106 	cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
    107 	cutlim = cutoff % (unsigned long)base;
    108 	cutoff /= (unsigned long)base;
    109 	for (acc = 0, any = 0;; c = *s++) {
    110 		if (isdigit(c))
    111 			c -= '0';
    112 		else if (isalpha(c))
    113 			c -= isupper(c) ? 'A' - 10 : 'a' - 10;
    114 		else
    115 			break;
    116 		if (c >= base)
    117 			break;
    118 		if (any < 0 || acc > cutoff || acc == cutoff && c > cutlim)
    119 			any = -1;
    120 		else {
    121 			any = 1;
    122 			acc *= (unsigned long)base;
    123 			acc += c;
    124 		}
    125 	}
    126 	if (any < 0) {
    127 		acc = neg ? LONG_MIN : LONG_MAX;
    128 		errno = ERANGE;
    129 	} else if (neg)
    130 		acc = -acc;
    131 	if (endptr != 0)
    132 		*endptr = (char *) (any ? s - 1 : nptr);
    133 	return (acc);
    134 }
    135