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  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  * From: @(#)strtol.c   8.1 (Berkeley) 6/4/93
   33  */
   34 
   35 #include <sys/cdefs.h>
   36 __FBSDID("$FreeBSD: releng/8.3/sys/libkern/strtol.c 199583 2009-11-20 15:27:52Z jhb $");
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h>
   40 #include <sys/ctype.h>
   41 #include <sys/limits.h>
   42 
   43 /*
   44  * Convert a string to a long integer.
   45  *
   46  * Ignores `locale' stuff.  Assumes that the upper and lower case
   47  * alphabets and digits are each contiguous.
   48  */
   49 long
   50 strtol(nptr, endptr, base)
   51         const char *nptr;
   52         char **endptr;
   53         int base;
   54 {
   55         const char *s = nptr;
   56         unsigned long acc;
   57         unsigned char c;
   58         unsigned long cutoff;
   59         int neg = 0, any, cutlim;
   60 
   61         /*
   62          * Skip white space and pick up leading +/- sign if any.
   63          * If base is 0, allow 0x for hex and 0 for octal, else
   64          * assume decimal; if base is already 16, allow 0x.
   65          */
   66         do {
   67                 c = *s++;
   68         } while (isspace(c));
   69         if (c == '-') {
   70                 neg = 1;
   71                 c = *s++;
   72         } else if (c == '+')
   73                 c = *s++;
   74         if ((base == 0 || base == 16) &&
   75             c == '' && (*s == 'x' || *s == 'X')) {
   76                 c = s[1];
   77                 s += 2;
   78                 base = 16;
   79         }
   80         if (base == 0)
   81                 base = c == '' ? 8 : 10;
   82 
   83         /*
   84          * Compute the cutoff value between legal numbers and illegal
   85          * numbers.  That is the largest legal value, divided by the
   86          * base.  An input number that is greater than this value, if
   87          * followed by a legal input character, is too big.  One that
   88          * is equal to this value may be valid or not; the limit
   89          * between valid and invalid numbers is then based on the last
   90          * digit.  For instance, if the range for longs is
   91          * [-2147483648..2147483647] and the input base is 10,
   92          * cutoff will be set to 214748364 and cutlim to either
   93          * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
   94          * a value > 214748364, or equal but the next digit is > 7 (or 8),
   95          * the number is too big, and we will return a range error.
   96          *
   97          * Set any if any `digits' consumed; make it negative to indicate
   98          * overflow.
   99          */
  100         cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
  101         cutlim = cutoff % (unsigned long)base;
  102         cutoff /= (unsigned long)base;
  103         for (acc = 0, any = 0;; c = *s++) {
  104                 if (!isascii(c))
  105                         break;
  106                 if (isdigit(c))
  107                         c -= '';
  108                 else if (isalpha(c))
  109                         c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  110                 else
  111                         break;
  112                 if (c >= base)
  113                         break;
  114                 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
  115                         any = -1;
  116                 else {
  117                         any = 1;
  118                         acc *= base;
  119                         acc += c;
  120                 }
  121         }
  122         if (any < 0) {
  123                 acc = neg ? LONG_MIN : LONG_MAX;
  124         } else if (neg)
  125                 acc = -acc;
  126         if (endptr != 0)
  127                 *((const char **)endptr) = any ? s - 1 : nptr;
  128         return (acc);
  129 }

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