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. All advertising materials mentioning features or use of this software
   17  *    must display the following acknowledgement:
   18  *      This product includes software developed by the University of
   19  *      California, Berkeley and its contributors.
   20  * 4. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  * $FreeBSD: src/sys/libkern/strtoq.c,v 1.4 2003/04/29 13:36:04 kan Exp $
   37  */
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/ctype.h>
   42 #include <sys/limits.h>
   43 
   44 /*
   45  * Convert a string to a quad integer.
   46  *
   47  * Ignores `locale' stuff.  Assumes that the upper and lower case
   48  * alphabets and digits are each contiguous.
   49  */
   50 quad_t
   51 strtoq(const char *nptr, char **endptr, int base)
   52 {
   53         const char *s;
   54         u_quad_t acc;
   55         unsigned char c;
   56         u_quad_t qbase, cutoff;
   57         int neg, any, cutlim;
   58 
   59         /*
   60          * Skip white space and pick up leading +/- sign if any.
   61          * If base is 0, allow 0x for hex and 0 for octal, else
   62          * assume decimal; if base is already 16, allow 0x.
   63          */
   64         s = nptr;
   65         do {
   66                 c = *s++;
   67         } while (isspace(c));
   68         if (c == '-') {
   69                 neg = 1;
   70                 c = *s++;
   71         } else {
   72                 neg = 0;
   73                 if (c == '+')
   74                         c = *s++;
   75         }
   76         if ((base == 0 || base == 16) &&
   77             c == '' && (*s == 'x' || *s == 'X')) {
   78                 c = s[1];
   79                 s += 2;
   80                 base = 16;
   81         }
   82         if (base == 0)
   83                 base = c == '' ? 8 : 10;
   84 
   85         /*
   86          * Compute the cutoff value between legal numbers and illegal
   87          * numbers.  That is the largest legal value, divided by the
   88          * base.  An input number that is greater than this value, if
   89          * followed by a legal input character, is too big.  One that
   90          * is equal to this value may be valid or not; the limit
   91          * between valid and invalid numbers is then based on the last
   92          * digit.  For instance, if the range for quads is
   93          * [-9223372036854775808..9223372036854775807] and the input base
   94          * is 10, cutoff will be set to 922337203685477580 and cutlim to
   95          * either 7 (neg==0) or 8 (neg==1), meaning that if we have
   96          * accumulated a value > 922337203685477580, or equal but the
   97          * next digit is > 7 (or 8), the number is too big, and we will
   98          * return a range error.
   99          *
  100          * Set any if any `digits' consumed; make it negative to indicate
  101          * overflow.
  102          */
  103         qbase = (unsigned)base;
  104         cutoff = neg ? (u_quad_t)-(QUAD_MIN + QUAD_MAX) + QUAD_MAX : QUAD_MAX;
  105         cutlim = cutoff % qbase;
  106         cutoff /= qbase;
  107         for (acc = 0, any = 0;; c = *s++) {
  108                 if (!isascii(c))
  109                         break;
  110                 if (isdigit(c))
  111                         c -= '';
  112                 else if (isalpha(c))
  113                         c -= isupper(c) ? 'A' - 10 : 'a' - 10;
  114                 else
  115                         break;
  116                 if (c >= base)
  117                         break;
  118                 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
  119                         any = -1;
  120                 else {
  121                         any = 1;
  122                         acc *= qbase;
  123                         acc += c;
  124                 }
  125         }
  126         if (any < 0) {
  127                 acc = neg ? QUAD_MIN : QUAD_MAX;
  128         } else if (neg)
  129                 acc = -acc;
  130         if (endptr != 0)
  131                 *((const char **)endptr) = any ? s - 1 : nptr;
  132         return (acc);
  133 }

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