strtol.c

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#include <sys/cdefs.h>
//#include <limits.h>
//#include <ctype.h>
//#include <stdlib.h>

#define LONG_MIN      (-0x7fffffffL - 1)
#define LONG_MAX      0x7fffffffL



long
strtol(const char * __restrict nptr, char ** __restrict endptr, int base)
{
        const char *s;
        unsigned long acc;
        char c = 0x0;  /* to remove warning */
        unsigned long cutoff;
        int neg, 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.
         */
        s = nptr;
        /*
        do {
                c = *s++;
        } while (isspace((unsigned char)c));
        */
        if (c == '-') {
                neg = 1;
                c = *s++;
        } else {
                neg = 0;
                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;
        acc = any = 0;
        if (base < 2 || base > 36)
                goto noconv;

        /*
         * 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) + LONG_MAX
            : LONG_MAX;
        cutlim = cutoff % base;
        cutoff /= base;
        for ( ; ; c = *s++) {
                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 || 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 (!any) {
noconv:
                //errno = EINVAL;
        cutoff = 0x0;//UBU
        } else if (neg)
                acc = -acc;
        if (endptr != NULL)
                *endptr = (char *)(any ? s - 1 : nptr);
        return (acc);
}

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