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/strtoq.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 
   33 #include <sys/cdefs.h>
   34 __FBSDID("$FreeBSD$");
   35 
   36 #include <sys/param.h>
   37 #include <sys/systm.h>
   38 #include <sys/ctype.h>
   39 #include <sys/limits.h>
   40 
   41 /*
   42  * Convert a string to a quad integer.
   43  *
   44  * Ignores `locale' stuff.  Assumes that the upper and lower case
   45  * alphabets and digits are each contiguous.
   46  */
   47 quad_t
   48 strtoq(const char *nptr, char **endptr, int base)
   49 {
   50         const char *s;
   51         u_quad_t acc;
   52         unsigned char c;
   53         u_quad_t qbase, cutoff;
   54         int neg, any, cutlim;
   55 
   56         /*
   57          * Skip white space and pick up leading +/- sign if any.
   58          * If base is 0, allow 0x for hex and 0 for octal, else
   59          * assume decimal; if base is already 16, allow 0x.
   60          */
   61         s = nptr;
   62         do {
   63                 c = *s++;
   64         } while (isspace(c));
   65         if (c == '-') {
   66                 neg = 1;
   67                 c = *s++;
   68         } else {
   69                 neg = 0;
   70                 if (c == '+')
   71                         c = *s++;
   72         }
   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 quads is
   90          * [-9223372036854775808..9223372036854775807] and the input base
   91          * is 10, cutoff will be set to 922337203685477580 and cutlim to
   92          * either 7 (neg==0) or 8 (neg==1), meaning that if we have
   93          * accumulated a value > 922337203685477580, or equal but the
   94          * next digit is > 7 (or 8), the number is too big, and we will
   95          * return a range error.
   96          *
   97          * Set any if any `digits' consumed; make it negative to indicate
   98          * overflow.
   99          */
  100         qbase = (unsigned)base;
  101         cutoff = neg ? (u_quad_t)-(QUAD_MIN + QUAD_MAX) + QUAD_MAX : QUAD_MAX;
  102         cutlim = cutoff % qbase;
  103         cutoff /= qbase;
  104         for (acc = 0, any = 0;; c = *s++) {
  105                 if (!isascii(c))
  106                         break;
  107                 if (isdigit(c))
  108                         c -= '';
  109                 else if (isalpha(c))
  110                         c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  111                 else
  112                         break;
  113                 if (c >= base)
  114                         break;
  115                 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
  116                         any = -1;
  117                 else {
  118                         any = 1;
  119                         acc *= qbase;
  120                         acc += c;
  121                 }
  122         }
  123         if (any < 0) {
  124                 acc = neg ? QUAD_MIN : QUAD_MAX;
  125         } else if (neg)
  126                 acc = -acc;
  127         if (endptr != 0)
  128                 *((const char **)endptr) = any ? s - 1 : nptr;
  129         return (acc);
  130 }

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