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  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1990, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * This code is derived from software contributed to Berkeley by
    8  * Chris Torek.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 3. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  * From: @(#)strtol.c   8.1 (Berkeley) 6/4/93
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD$");
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/ctype.h>
   43 #include <sys/limits.h>
   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(const char *nptr, char **endptr, int base)
   53 {
   54         const char *s = nptr;
   55         unsigned long acc;
   56         unsigned char c;
   57         unsigned long cutoff;
   58         int neg = 0, any, cutlim;
   59 
   60         /*
   61          * Skip white space and pick up leading +/- sign if any.
   62          * If base is 0, allow 0x for hex and 0 for octal, else
   63          * assume decimal; if base is already 16, allow 0x.
   64          */
   65         do {
   66                 c = *s++;
   67         } while (isspace(c));
   68         if (c == '-') {
   69                 neg = 1;
   70                 c = *s++;
   71         } else if (c == '+')
   72                 c = *s++;
   73         if ((base == 0 || base == 16) &&
   74             c == '' && (*s == 'x' || *s == 'X')) {
   75                 c = s[1];
   76                 s += 2;
   77                 base = 16;
   78         }
   79         if (base == 0)
   80                 base = c == '' ? 8 : 10;
   81 
   82         /*
   83          * Compute the cutoff value between legal numbers and illegal
   84          * numbers.  That is the largest legal value, divided by the
   85          * base.  An input number that is greater than this value, if
   86          * followed by a legal input character, is too big.  One that
   87          * is equal to this value may be valid or not; the limit
   88          * between valid and invalid numbers is then based on the last
   89          * digit.  For instance, if the range for longs is
   90          * [-2147483648..2147483647] and the input base is 10,
   91          * cutoff will be set to 214748364 and cutlim to either
   92          * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
   93          * a value > 214748364, or equal but the next digit is > 7 (or 8),
   94          * the number is too big, and we will return a range error.
   95          *
   96          * Set any if any `digits' consumed; make it negative to indicate
   97          * overflow.
   98          */
   99         cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
  100         cutlim = cutoff % (unsigned long)base;
  101         cutoff /= (unsigned long)base;
  102         for (acc = 0, any = 0;; c = *s++) {
  103                 if (!isascii(c))
  104                         break;
  105                 if (isdigit(c))
  106                         c -= '';
  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 || acc > cutoff || (acc == cutoff && c > cutlim))
  114                         any = -1;
  115                 else {
  116                         any = 1;
  117                         acc *= base;
  118                         acc += c;
  119                 }
  120         }
  121         if (any < 0) {
  122                 acc = neg ? LONG_MIN : LONG_MAX;
  123         } else if (neg)
  124                 acc = -acc;
  125         if (endptr != NULL)
  126                 *endptr = __DECONST(char *, any ? s - 1 : nptr);
  127         return (acc);
  128 }

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