The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/libkern/strtol.c

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    1 /*-
    2  * Copyright (c) 1990, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * Chris Torek.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. All advertising materials mentioning features or use of this software
   17  *    must display the following acknowledgement:
   18  *      This product includes software developed by the University of
   19  *      California, Berkeley and its contributors.
   20  * 4. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  * From: static char sccsid[] = "@(#)strtol.c   8.1 (Berkeley) 6/4/93";
   37  *
   38  * $FreeBSD: releng/5.1/sys/libkern/strtol.c 114216 2003-04-29 13:36:06Z kan $
   39  */
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/ctype.h>
   44 #include <sys/limits.h>
   45 
   46 /*
   47  * Convert a string to a long integer.
   48  *
   49  * Ignores `locale' stuff.  Assumes that the upper and lower case
   50  * alphabets and digits are each contiguous.
   51  */
   52 long
   53 strtol(nptr, endptr, base)
   54         const char *nptr;
   55         char **endptr;
   56         int base;
   57 {
   58         const char *s = nptr;
   59         unsigned long acc;
   60         unsigned char c;
   61         unsigned long cutoff;
   62         int neg = 0, any, cutlim;
   63 
   64         /*
   65          * Skip white space and pick up leading +/- sign if any.
   66          * If base is 0, allow 0x for hex and 0 for octal, else
   67          * assume decimal; if base is already 16, allow 0x.
   68          */
   69         do {
   70                 c = *s++;
   71         } while (isspace(c));
   72         if (c == '-') {
   73                 neg = 1;
   74                 c = *s++;
   75         } else if (c == '+')
   76                 c = *s++;
   77         if ((base == 0 || base == 16) &&
   78             c == '' && (*s == 'x' || *s == 'X')) {
   79                 c = s[1];
   80                 s += 2;
   81                 base = 16;
   82         }
   83         if (base == 0)
   84                 base = c == '' ? 8 : 10;
   85 
   86         /*
   87          * Compute the cutoff value between legal numbers and illegal
   88          * numbers.  That is the largest legal value, divided by the
   89          * base.  An input number that is greater than this value, if
   90          * followed by a legal input character, is too big.  One that
   91          * is equal to this value may be valid or not; the limit
   92          * between valid and invalid numbers is then based on the last
   93          * digit.  For instance, if the range for longs is
   94          * [-2147483648..2147483647] and the input base is 10,
   95          * cutoff will be set to 214748364 and cutlim to either
   96          * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
   97          * a value > 214748364, or equal but the next digit is > 7 (or 8),
   98          * the number is too big, and we will return a range error.
   99          *
  100          * Set any if any `digits' consumed; make it negative to indicate
  101          * overflow.
  102          */
  103         cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
  104         cutlim = cutoff % (unsigned long)base;
  105         cutoff /= (unsigned long)base;
  106         for (acc = 0, any = 0;; c = *s++) {
  107                 if (!isascii(c))
  108                         break;
  109                 if (isdigit(c))
  110                         c -= '';
  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 *= base;
  122                         acc += c;
  123                 }
  124         }
  125         if (any < 0) {
  126                 acc = neg ? LONG_MIN : LONG_MAX;
  127         } else if (neg)
  128                 acc = -acc;
  129         if (endptr != 0)
  130                 *((const char **)endptr) = any ? s - 1 : nptr;
  131         return (acc);
  132 }

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