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. 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  * @(#)strtol.c 8.1 (Berkeley) 6/4/93
  34  * $DragonFly: src/lib/libstand/strtol.c,v 1.4 2005/12/11 03:27:26 swildner Exp $
  35  */
  36
  37 #include "stand.h"
  38 #include <limits.h>
  39
  40 /*
  41  * Convert a string to a long integer.
  42  *
  43  * Ignores `locale' stuff.  Assumes that the upper and lower case
  44  * alphabets and digits are each contiguous.
  45  */
  46 long
  47 strtol(const char *nptr, char **endptr, int base)
  48 {
  49         const char *s;
  50         unsigned long acc;
  51         unsigned char c;
  52         unsigned long cutoff;
  53         int neg = 0, any, cutlim;
  54
  55         /* Be sensible about NULL strings */
  56         if (nptr == NULL)
  57             nptr = "";
  58         s = nptr;
  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 == '0' && (*s == 'x' || *s == 'X')) {
  75                 c = s[1];
  76                 s += 2;
  77                 base = 16;
  78         }
  79         if (base == 0)
  80                 base = c == '0' ? 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 -= '0';
 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                 errno = ERANGE;
 124         } else if (neg)
 125                 acc = -acc;
 126         if (endptr != 0)
 127                 *endptr = (char *)(any ? s - 1 : nptr);
 128         return (acc);
 129 }