FreeBSD/Linux Kernel Cross Reference
sys/libkern/strtoq.c

     /*-
      * Copyright (c) 1990, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * Chris Torek.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/ctype.h>
    #include <sys/limits.h>
    
    /*
     * Convert a string to a quad integer.
     *
     * Ignores `locale' stuff.  Assumes that the upper and lower case
     * alphabets and digits are each contiguous.
     */
    quad_t
    strtoq(const char *nptr, char **endptr, int base)
    {
            const char *s;
            u_quad_t acc;
            unsigned char c;
            u_quad_t qbase, cutoff;
            int neg, any, cutlim;
    
            /*
             * Skip white space and pick up leading +/- sign if any.
             * If base is 0, allow 0x for hex and 0 for octal, else
             * assume decimal; if base is already 16, allow 0x.
             */
            s = nptr;
            do {
                    c = *s++;
            } while (isspace(c));
            if (c == '-') {
                    neg = 1;
                    c = *s++;
            } else {
                    neg = 0;
                    if (c == '+')
                            c = *s++;
            }
            if ((base == 0 || base == 16) &&
                c == '' && (*s == 'x' || *s == 'X')) {
                    c = s[1];
                    s += 2;
                    base = 16;
            }
            if (base == 0)
                    base = c == '' ? 8 : 10;
    
            /*
             * Compute the cutoff value between legal numbers and illegal
             * numbers.  That is the largest legal value, divided by the
             * base.  An input number that is greater than this value, if
             * followed by a legal input character, is too big.  One that
             * is equal to this value may be valid or not; the limit
             * between valid and invalid numbers is then based on the last
             * digit.  For instance, if the range for quads is
             * [-9223372036854775808..9223372036854775807] and the input base
             * is 10, cutoff will be set to 922337203685477580 and cutlim to
             * either 7 (neg==0) or 8 (neg==1), meaning that if we have
             * accumulated a value > 922337203685477580, or equal but the
             * next digit is > 7 (or 8), the number is too big, and we will
             * return a range error.
             *
             * Set any if any `digits' consumed; make it negative to indicate
             * overflow.
             */
           qbase = (unsigned)base;
           cutoff = neg ? (u_quad_t)-(QUAD_MIN + QUAD_MAX) + QUAD_MAX : QUAD_MAX;
           cutlim = cutoff % qbase;
           cutoff /= qbase;
           for (acc = 0, any = 0;; c = *s++) {
                   if (!isascii(c))
                           break;
                   if (isdigit(c))
                           c -= '';
                   else if (isalpha(c))
                           c -= isupper(c) ? 'A' - 10 : 'a' - 10;
                   else
                           break;
                   if (c >= base)
                           break;
                   if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
                           any = -1;
                   else {
                           any = 1;
                           acc *= qbase;
                           acc += c;
                   }
           }
           if (any < 0) {
                   acc = neg ? QUAD_MIN : QUAD_MAX;
           } else if (neg)
                   acc = -acc;
           if (endptr != 0)
                   *((const char **)endptr) = any ? s - 1 : nptr;
           return (acc);
   }

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