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. 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 == '0' && (*s == 'x' || *s == 'X')) {
  74                 c = s[1];
  75                 s += 2;
  76                 base = 16;
  77         }
  78         if (base == 0)
  79                 base = c == '0' ? 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 -= '0';
 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 }