strtol.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 a long integer.
 *
 * Ignores `locale' stuff.  Assumes that the upper and lower case
 * alphabets and digits are each contiguous.
 */
ATTRIBUTE_CLIB_SECTION
long
strtol(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;

        /*
         * 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 = *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;

        /*
         * 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 decision
         * about this is done as outlined below.
         *
         * Overflow detections works as follows:
         *
         * As:
         *    acc_old <= cutoff
         * then:
         *    acc_old * base <= 0x80000000        (unsigned)
         * then:
         *    acc_old * base + c <= 0x80000000 + c
         * or:
         *    acc_new <= 0x80000000 + 35
         *
         * i.e. carry from MSB (by calculating acc_new) is impossible
         * and we can check result directly:
         *
         *    if (acc_new > 0x80000000) then overflow
         *
         * Set any if any `digits' consumed; make it negative to indicate
         * overflow.
         */
#if  LONG_MIN != -LONG_MAX - 1
#  error "This implementation of strtol() does not work on this platform."
#endif
        switch (base) {
            case 10:
                cutoff = ((unsigned long)LONG_MAX + 1) / 10;
                break;
            case 16:
                cutoff = ((unsigned long)LONG_MAX + 1) / 16;
                break;
            case 8:
                cutoff = ((unsigned long)LONG_MAX + 1) / 8;
                break;
            case 2:
                cutoff = ((unsigned long)LONG_MAX + 1) / 2;
                break;
            default:
                cutoff = ((unsigned long)LONG_MAX + 1) / 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;
                if (acc > (unsigned long)LONG_MAX + 1)
                        any = -1;
                else
                        any = 1;
        }
        if (endptr) {
                if (any)
                    *endptr = (char *)nptr - 1;
                else if (flag & FL_0X)
                    *endptr = (char *)nptr - 2;
        }
        if (any < 0) {
                acc = (flag & FL_NEG) ? LONG_MIN : LONG_MAX;
                errno = ERANGE;
        } else if (flag & FL_NEG) {
                acc = -acc;
        } else if ((signed long)acc < 0) {
                acc = LONG_MAX;
                errno = ERANGE;
        }
        return (acc);
}