sys/libkern/strtoq.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. 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 1.3 1999/12/01 22:56:51 archie Exp $
  37  * $DragonFly: src/sys/libkern/strtoq.c,v 1.2 2003/06/17 04:28:42 dillon Exp $
  38  */
  39
  40 #include <sys/param.h>
  41 #include <sys/systm.h>
  42 #include <sys/ctype.h>
  43 #include <machine/limits.h>
  44
  45 /*
  46  * Convert a string to a quad integer.
  47  *
  48  * Ignores `locale' stuff.  Assumes that the upper and lower case
  49  * alphabets and digits are each contiguous.
  50  */
  51 quad_t
  52 strtoq(const char *nptr, char **endptr, int base)
  53 {
  54         const char *s;
  55         u_quad_t acc;
  56         unsigned char c;
  57         u_quad_t qbase, cutoff;
  58         int neg, any, cutlim;
  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         s = nptr;
  66         do {
  67                 c = *s++;
  68         } while (isspace(c));
  69         if (c == '-') {
  70                 neg = 1;
  71                 c = *s++;
  72         } else {
  73                 neg = 0;
  74                 if (c == '+')
  75                         c = *s++;
  76         }
  77         if ((base == 0 || base == 16) &&
  78             c == '0' && (*s == 'x' || *s == 'X')) {
  79                 c = s[1];
  80                 s += 2;
  81                 base = 16;
  82         }
  83         if (base == 0)
  84                 base = c == '0' ? 8 : 10;
  85
  86         /*
  87          * Compute the cutoff value between legal numbers and illegal
  88          * numbers.  That is the largest legal value, divided by the
  89          * base.  An input number that is greater than this value, if
  90          * followed by a legal input character, is too big.  One that
  91          * is equal to this value may be valid or not; the limit
  92          * between valid and invalid numbers is then based on the last
  93          * digit.  For instance, if the range for quads is
  94          * [-9223372036854775808..9223372036854775807] and the input base
  95          * is 10, cutoff will be set to 922337203685477580 and cutlim to
  96          * either 7 (neg==0) or 8 (neg==1), meaning that if we have
  97          * accumulated a value > 922337203685477580, or equal but the
  98          * next digit is > 7 (or 8), the number is too big, and we will
  99          * return a range error.
 100          *
 101          * Set any if any `digits' consumed; make it negative to indicate
 102          * overflow.
 103          */
 104         qbase = (unsigned)base;
 105         cutoff = neg ? (u_quad_t)-(QUAD_MIN + QUAD_MAX) + QUAD_MAX : QUAD_MAX;
 106         cutlim = cutoff % qbase;
 107         cutoff /= qbase;
 108         for (acc = 0, any = 0;; c = *s++) {
 109                 if (!isascii(c))
 110                         break;
 111                 if (isdigit(c))
 112                         c -= '0';
 113                 else if (isalpha(c))
 114                         c -= isupper(c) ? 'A' - 10 : 'a' - 10;
 115                 else
 116                         break;
 117                 if (c >= base)
 118                         break;
 119                 if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
 120                         any = -1;
 121                 else {
 122                         any = 1;
 123                         acc *= qbase;
 124                         acc += c;
 125                 }
 126         }
 127         if (any < 0) {
 128                 acc = neg ? QUAD_MIN : QUAD_MAX;
 129         } else if (neg)
 130                 acc = -acc;
 131         if (endptr != 0)
 132                 *((const char **)endptr) = any ? s - 1 : nptr;
 133         return (acc);
 134 }