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  * 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  * $FreeBSD: src/sys/libkern/strtoq.c,v 1.3 1999/12/01 22:56:51 archie Exp $
   33  */
   34 
   35 #include <sys/param.h>
   36 #include <sys/systm.h>
   37 #include <sys/ctype.h>
   38 #include <machine/limits.h>
   39 
   40 /*
   41  * Convert a string to a quad integer.
   42  *
   43  * Ignores `locale' stuff.  Assumes that the upper and lower case
   44  * alphabets and digits are each contiguous.
   45  */
   46 quad_t
   47 strtoq(const char *nptr, char **endptr, int base)
   48 {
   49         const char *s;
   50         u_quad_t acc;
   51         unsigned char c;
   52         u_quad_t qbase, cutoff;
   53         int neg, any, cutlim;
   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         s = nptr;
   61         do {
   62                 c = *s++;
   63         } while (isspace(c));
   64         if (c == '-') {
   65                 neg = 1;
   66                 c = *s++;
   67         } else {
   68                 neg = 0;
   69                 if (c == '+')
   70                         c = *s++;
   71         }
   72         if ((base == 0 || base == 16) &&
   73             c == '' && (*s == 'x' || *s == 'X')) {
   74                 c = s[1];
   75                 s += 2;
   76                 base = 16;
   77         }
   78         if (base == 0)
   79                 base = c == '' ? 8 : 10;
   80 
   81         /*
   82          * Compute the cutoff value between legal numbers and illegal
   83          * numbers.  That is the largest legal value, divided by the
   84          * base.  An input number that is greater than this value, if
   85          * followed by a legal input character, is too big.  One that
   86          * is equal to this value may be valid or not; the limit
   87          * between valid and invalid numbers is then based on the last
   88          * digit.  For instance, if the range for quads is
   89          * [-9223372036854775808..9223372036854775807] and the input base
   90          * is 10, cutoff will be set to 922337203685477580 and cutlim to
   91          * either 7 (neg==0) or 8 (neg==1), meaning that if we have
   92          * accumulated a value > 922337203685477580, or equal but the
   93          * next digit is > 7 (or 8), the number is too big, and we will
   94          * return a range error.
   95          *
   96          * Set any if any `digits' consumed; make it negative to indicate
   97          * overflow.
   98          */
   99         qbase = (unsigned)base;
  100         cutoff = neg ? (u_quad_t)-(QUAD_MIN + QUAD_MAX) + QUAD_MAX : QUAD_MAX;
  101         cutlim = cutoff % qbase;
  102         cutoff /= qbase;
  103         for (acc = 0, any = 0;; c = *s++) {
  104                 if (!isascii(c))
  105                         break;
  106                 if (isdigit(c))
  107                         c -= '';
  108                 else if (isalpha(c))
  109                         c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  110                 else
  111                         break;
  112                 if (c >= base)
  113                         break;
  114                 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
  115                         any = -1;
  116                 else {
  117                         any = 1;
  118                         acc *= qbase;
  119                         acc += c;
  120                 }
  121         }
  122         if (any < 0) {
  123                 acc = neg ? QUAD_MIN : QUAD_MAX;
  124         } else if (neg)
  125                 acc = -acc;
  126         if (endptr != NULL)
  127                 *((const char **)(void *)endptr) = any ? s - 1 : nptr;
  128         return (acc);
  129 }

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