strtoul.c

/*
 * Copyright (c) 1990, 1993
 *  The Regents of the University of California.  All rights reserved.
 * Copyright (c) 2005, Dmitry Xmelkov
 *
 * 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.
 *
 * $Id$
 */

#include <limits.h>
#include <ctype.h>
#include <errno.h>
#include <stdlib.h>
#include "sectionname.h"

/*
 * Convert a string to an unsigned long integer.
 *
 * Ignores `locale' stuff.  Assumes that the upper and lower case
 * alphabets and digits are each contiguous.
 */
ATTRIBUTE_CLIB_SECTION
unsigned long
strtoul(const char *nptr, char **endptr, register int base)
{
    register unsigned long acc;
    register unsigned char c;
    register unsigned long cutoff;
    register signed char any;
    unsigned char flag = 0;
#define FL_NEG  0x01        /* number is negative */
#define FL_0X   0x02        /* number has a 0x prefix */

    if (endptr)
        *endptr = (char *)nptr;
    if (base != 0 && (base < 2 || base > 36))
        return 0;

    /*
     * See strtol for comments as to the logic used.
     */
    do {
        c = *nptr++;
    } while (isspace(c));
    if (c == '-') {
        flag = FL_NEG;
        c = *nptr++;
    } else if (c == '+')
        c = *nptr++;
    if ((base == 0 || base == 16) &&
        c == '0' && (*nptr == 'x' || *nptr == 'X')) {
        c = nptr[1];
        nptr += 2;
        base = 16;
        flag |= FL_0X;
    }
    if (base == 0)
        base = c == '0' ? 8 : 10;

    /*
     * cutoff computation is similar to strtol().
     *
     * Description of the overflow detection logic used.
     *
     * First, let us assume an overflow.
     *
     * Result of `acc_old * base + c' is cut to 32 bits:
     *  acc_new <-- acc_old * base + c - 0x100000000
     *
     *  `acc_old * base' is <= 0xffffffff   (cutoff control)
     *
     * then:   acc_new <= 0xffffffff + c - 0x100000000
     *
     * or:     acc_new <= c - 1
     *
     * or:     acc_new < c
     *
     * Second:
     * if (no overflow) then acc * base + c >= c
     *                        (or: acc_new >= c)
     * is clear (alls are unsigned).
     *
     */
    switch (base) {
        case 16:    cutoff = ULONG_MAX / 16;  break;
        case 10:    cutoff = ULONG_MAX / 10;  break;
        case 8:     cutoff = ULONG_MAX / 8;   break;
        default:    cutoff = ULONG_MAX / base;
    }

    for (acc = 0, any = 0;; c = *nptr++) {
        if (c >= '0' && c <= '9')
            c -= '0';
        else if (c >= 'A' && c <= 'Z')
            c -= 'A' - 10;
        else if (c >= 'a' && c <= 'z')
            c -= 'a' - 10;
        else
            break;
        if (c >= base)
            break;
        if (any < 0)
            continue;
        if (acc > cutoff) {
            any = -1;
            continue;
        }
        acc = acc * base + c;
        any = (c > acc) ? -1 : 1;
    }

    if (endptr) {
        if (any)
            *endptr = (char *)nptr - 1;
        else if (flag & FL_0X)
            *endptr = (char *)nptr - 2;
    }
    if (flag & FL_NEG)
        acc = -acc;
    if (any < 0) {
        acc = ULONG_MAX;
        errno = ERANGE;
    }
    return (acc);
}