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strtoul.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.
 *
 * From: @(#)strtoul.c  8.1 (Berkeley) 6/4/93
 */

/* $FreeBSD: src/sys/libkern/strtoul.c,v 1.6.32.1 2010/02/10 00:26:20 kensmith Exp $ */

#include <ctype.h>
#include <string.h>

#define ULONG_MAX     0xFFFFFFFFUL

/*
 * Convert a string to an unsigned long integer.
 *
 * Ignores `locale' stuff.  Assumes that the upper and lower case
 * alphabets and digits are each contiguous.
 */
unsigned long strtoul(const char *nptr, char **endptr, int base)
{
      const char *s = nptr;
      unsigned long acc;
      unsigned char c;
      unsigned long cutoff;
      int neg = 0, any, cutlim;

      /*
       * See strtol for comments as to the logic used.
       */
      do {
            c = *s++;
      } while (isspace(c));
      if (c == '-') {
            neg = 1;
            c = *s++;
      } else if (c == '+')
            c = *s++;
      if ((base == 0 || base == 16) &&
          c == '0' && (*s == 'x' || *s == 'X')) {
            c = s[1];
            s += 2;
            base = 16;
      }
      if (base == 0)
            base = c == '0' ? 8 : 10;
      cutoff = (unsigned long)ULONG_MAX / (unsigned long)base;
      cutlim = (unsigned long)ULONG_MAX % (unsigned long)base;
      for (acc = 0, any = 0;; c = *s++) {
            if (isdigit(c))
                  c -= '0';
            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 *= base;
                  acc += c;
            }
      }
      if (any < 0) {
            acc = ULONG_MAX;
      } else if (neg)
            acc = -acc;
      if (endptr != 0)
            *((const char **)endptr) = any ? s - 1 : nptr;
      return (acc);
}

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