sys/libkern/strtol.c

   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. 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: static char sccsid[] = "@(#)strtol.c   8.1 (Berkeley) 6/4/93";
  33  *
  34  * $FreeBSD: src/sys/libkern/strtol.c,v 1.5 1999/12/01 22:56:50 archie Exp $
  35  */
  36
  37 #include <sys/param.h>
  38 #include <sys/systm.h>
  39 #include <sys/ctype.h>
  40 #include <machine/limits.h>
  41
  42 /*
  43  * Convert a string to a long integer.
  44  *
  45  * Ignores `locale' stuff.  Assumes that the upper and lower case
  46  * alphabets and digits are each contiguous.
  47  */
  48 long
  49 strtol(const char *nptr, char **endptr, int base)
  50 {
  51         const char *s = nptr;
  52         unsigned long acc;
  53         unsigned char c;
  54         unsigned long cutoff;
  55         int neg = 0, any, cutlim;
  56
  57         /*
  58          * Skip white space and pick up leading +/- sign if any.
  59          * If base is 0, allow 0x for hex and 0 for octal, else
  60          * assume decimal; if base is already 16, allow 0x.
  61          */
  62         do {
  63                 c = *s++;
  64         } while (isspace(c));
  65         if (c == '-') {
  66                 neg = 1;
  67                 c = *s++;
  68         } else if (c == '+')
  69                 c = *s++;
  70         if ((base == 0 || base == 16) &&
  71             c == '0' && (*s == 'x' || *s == 'X')) {
  72                 c = s[1];
  73                 s += 2;
  74                 base = 16;
  75         }
  76         if (base == 0)
  77                 base = c == '0' ? 8 : 10;
  78
  79         /*
  80          * Compute the cutoff value between legal numbers and illegal
  81          * numbers.  That is the largest legal value, divided by the
  82          * base.  An input number that is greater than this value, if
  83          * followed by a legal input character, is too big.  One that
  84          * is equal to this value may be valid or not; the limit
  85          * between valid and invalid numbers is then based on the last
  86          * digit.  For instance, if the range for longs is
  87          * [-2147483648..2147483647] and the input base is 10,
  88          * cutoff will be set to 214748364 and cutlim to either
  89          * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
  90          * a value > 214748364, or equal but the next digit is > 7 (or 8),
  91          * the number is too big, and we will return a range error.
  92          *
  93          * Set any if any `digits' consumed; make it negative to indicate
  94          * overflow.
  95          */
  96         cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
  97         cutlim = cutoff % (unsigned long)base;
  98         cutoff /= (unsigned long)base;
  99         for (acc = 0, any = 0;; c = *s++) {
 100                 if (!isascii(c))
 101                         break;
 102                 if (isdigit(c))
 103                         c -= '0';
 104                 else if (isalpha(c))
 105                         c -= isupper(c) ? 'A' - 10 : 'a' - 10;
 106                 else
 107                         break;
 108                 if (c >= base)
 109                         break;
 110                 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
 111                         any = -1;
 112                 else {
 113                         any = 1;
 114                         acc *= base;
 115                         acc += c;
 116                 }
 117         }
 118         if (any < 0) {
 119                 acc = neg ? LONG_MIN : LONG_MAX;
 120         } else if (neg)
 121                 acc = -acc;
 122         if (endptr != NULL)
 123                 *((const char **)(void *)endptr) = any ? s - 1 : nptr;
 124         return (acc);
 125 }