strtol.c

/*
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * 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.
 * 3. 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 <net-snmp/net-snmp-config.h>

#if defined(LIBC_SCCS) && !defined(lint)
static char     sccsid[] = "@(#)strtol.c    5.4 (Berkeley) 2/23/91";
#endif                          /* LIBC_SCCS and not lint */

#if HAVE_LIMITS_H
#include <limits.h>
#endif
#include <ctype.h>
#include <errno.h>
#if HAVE_STDLIB_H
#include <stdlib.h>
#endif

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

    /*
     * 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 longs
     * is [-2147483648..2147483647] and the input base is 10, cutoff will
     * be set to 214748364 and cutlim to either 7 (neg==0) or 8 (neg==1),
     * meaning that if we have accumulated a value > 214748364, 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.
     */
    cutoff = neg ? -(unsigned long) LONG_MIN : LONG_MAX;
    cutlim = cutoff % (unsigned long) base;
    cutoff /= (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 = neg ? LONG_MIN : LONG_MAX;
        errno = ERANGE;
    } else if (neg)
        acc = -acc;
    if (endptr != 0)
        *endptr = any ? s - 1 : (char *) nptr;
    return (acc);
}