strtol.c

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/*
 * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
 * See the copyright notice in the ACK home directory, in the file "Copyright".
 */
/* $Header: /opt/proj/minix/cvsroot/src/lib/ansi/strtol.c,v 1.1.1.1 2005/04/21 14:56:06 beng Exp $ */

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

static unsigned long
string2long(register const char *nptr, char **endptr,
                        int base, int is_signed);

long int
strtol(register const char *nptr, char **endptr, int base)
{
        return (signed long)string2long(nptr, endptr, base, 1);
}

unsigned long int
strtoul(register const char *nptr, char **endptr, int base)
{
        return (unsigned long)string2long(nptr, endptr, base, 0);
}

#define between(a, c, z)  ((unsigned) ((c) - (a)) <= (unsigned) ((z) - (a)))

static unsigned long
string2long(register const char *nptr, char ** const endptr,
                        int base, int is_signed)
{
        register unsigned int v;
        register unsigned long val = 0;
        register int c;
        int ovfl = 0, sign = 1;
        const char *startnptr = nptr, *nrstart;

        if (endptr) *endptr = (char *)nptr;
        while (isspace(*nptr)) nptr++;
        c = *nptr;

        if (c == '-' || c == '+') {
                if (c == '-') sign = -1;
                nptr++;
        }
        nrstart = nptr;                 /* start of the number */

        /* When base is 0, the syntax determines the actual base */
        if (base == 0)
                if (*nptr == '0')
                        if (*++nptr == 'x' || *nptr == 'X') {
                                base = 16;
                                nptr++;
                        }
                        else    base = 8;
                else    base = 10;
        else if (base==16 && *nptr=='0' && (*++nptr =='x' || *nptr =='X'))
                nptr++;

        for (;;) {
                c = *nptr;
                if (between('0', c, '9')) {
                        v = c - '0';
                } else
                if (between('a', c, 'z')) {
                        v = c - 'a' + 0xa;
                } else
                if (between('A', c, 'Z')) {
                        v = c - 'A' + 0xA;
                } else {
                        break;
                }
                if (v >= base) break;
                if (val > (ULONG_MAX - v) / base) ovfl++;
                val = (val * base) + v;
                nptr++;
        }
        if (endptr) {
                if (nrstart == nptr) *endptr = (char *)startnptr;
                else *endptr = (char *)nptr;
        }

        if (!ovfl) {
                /* Overflow is only possible when converting a signed long. */
                if (is_signed
                    && (   (sign < 0 && val > -(unsigned long)LONG_MIN)
                        || (sign > 0 && val > LONG_MAX)))
                    ovfl++;
        }

        if (ovfl) {
                errno = ERANGE;
                if (is_signed)
                        if (sign < 0) return LONG_MIN;
                        else return LONG_MAX;
                else return ULONG_MAX;
        }
        return (long) sign * val;
}

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