lib/libstand/strtol.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  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. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)strtol.c 8.1 (Berkeley) 6/4/93
  30  */
  31
  32 #include "stand.h"
  33 #include <limits.h>
  34
  35 /*
  36  * Convert a string to a long integer.
  37  *
  38  * Ignores `locale' stuff.  Assumes that the upper and lower case
  39  * alphabets and digits are each contiguous.
  40  */
  41 long
  42 strtol(const char *nptr, char **endptr, int base)
  43 {
  44         const char *s;
  45         unsigned long acc;
  46         unsigned char c;
  47         unsigned long cutoff;
  48         int neg = 0, any, cutlim;
  49
  50         /* Be sensible about NULL strings */
  51         if (nptr == NULL)
  52             nptr = "";
  53         s = nptr;
  54
  55         /*
  56          * Skip white space and pick up leading +/- sign if any.
  57          * If base is 0, allow 0x for hex and 0 for octal, else
  58          * assume decimal; if base is already 16, allow 0x.
  59          */
  60         do {
  61                 c = *s++;
  62         } while (isspace(c));
  63         if (c == '-') {
  64                 neg = 1;
  65                 c = *s++;
  66         } else if (c == '+')
  67                 c = *s++;
  68         if ((base == 0 || base == 16) &&
  69             c == '0' && (*s == 'x' || *s == 'X')) {
  70                 c = s[1];
  71                 s += 2;
  72                 base = 16;
  73         }
  74         if (base == 0)
  75                 base = c == '0' ? 8 : 10;
  76
  77         /*
  78          * Compute the cutoff value between legal numbers and illegal
  79          * numbers.  That is the largest legal value, divided by the
  80          * base.  An input number that is greater than this value, if
  81          * followed by a legal input character, is too big.  One that
  82          * is equal to this value may be valid or not; the limit
  83          * between valid and invalid numbers is then based on the last
  84          * digit.  For instance, if the range for longs is
  85          * [-2147483648..2147483647] and the input base is 10,
  86          * cutoff will be set to 214748364 and cutlim to either
  87          * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
  88          * a value > 214748364, or equal but the next digit is > 7 (or 8),
  89          * the number is too big, and we will return a range error.
  90          *
  91          * Set any if any `digits' consumed; make it negative to indicate
  92          * overflow.
  93          */
  94         cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
  95         cutlim = cutoff % (unsigned long)base;
  96         cutoff /= (unsigned long)base;
  97         for (acc = 0, any = 0;; c = *s++) {
  98                 if (!isascii(c))
  99                         break;
 100                 if (isdigit(c))
 101                         c -= '0';
 102                 else if (isalpha(c))
 103                         c -= isupper(c) ? 'A' - 10 : 'a' - 10;
 104                 else
 105                         break;
 106                 if (c >= base)
 107                         break;
 108                 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
 109                         any = -1;
 110                 else {
 111                         any = 1;
 112                         acc *= base;
 113                         acc += c;
 114                 }
 115         }
 116         if (any < 0) {
 117                 acc = neg ? LONG_MIN : LONG_MAX;
 118                 errno = ERANGE;
 119         } else if (neg)
 120                 acc = -acc;
 121         if (endptr != NULL)
 122                 *endptr = (char *)(any ? s - 1 : nptr);
 123         return (acc);
 124 }