strtoll.c File Reference

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

Include dependency graph for strtoll.c:

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Functions
long long int	strtoll (const char *nptr, char **endptr, int base)

Function Documentation

strtoll()

long long int strtoll	(	const char *	nptr,
		char **	endptr,
		int	base
	)

Definition at line 43 of file strtoll.c.

{
    const char* s;
    /* LONGLONG */
    long long int acc, cutoff;
    int c;
    int neg, any, cutlim;

    /* endptr may be NULL */

    // check base
    if(base < 0 || base > 36)
    {
        // errno = EINVAL

        if(endptr)
        {
            *endptr = (char*)(uintptr_t)nptr;
        }

        return 0;
    }

#ifdef __GNUC__
    /* This outrageous construct just to shut up a GCC warning. */
    (void)&acc;
    (void)&cutoff;
#endif

    /*
     * 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 = (unsigned char)*s++;
    } while(isspace(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;
        }
    }

    /*
     * 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 long longs is
     * [-9223372036854775808..9223372036854775807] and the input base
     * is 10, cutoff will be set to 922337203685477580 and cutlim to
     * either 7 (neg==0) or 8 (neg==1), meaning that if we have
     * accumulated a value > 922337203685477580, 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 ? LLONG_MIN : LLONG_MAX;
    cutlim = (int)(cutoff % base);
    cutoff /= base;
    if(neg)
    {
        if(cutlim > 0)
        {
            cutlim -= base;
            cutoff += 1;
        }
        cutlim = -cutlim;
    }
    for(acc = 0, any = 0;; c = (unsigned char)*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)
        {
            {
                continue;
            }
        }
        if(neg)
        {
            if(acc < cutoff || (acc == cutoff && c > cutlim))
            {
                any = -1;
                acc = LLONG_MIN;
                // errno = ERANGE;
            }
            else
            {
                any = 1;
                acc *= base;
                acc -= c;
            }
        }
        else
        {
            if(acc > cutoff || (acc == cutoff && c > cutlim))
            {
                any = -1;
                acc = LLONG_MAX;
                // errno = ERANGE;
            }
            else
            {
                any = 1;
                acc *= base;
                acc += c;
            }
        }
    }
    if(endptr != 0)
    {
        /* LINTED interface specification */
        *endptr = (char*)(uintptr_t)(any ? s - 1 : nptr);
    }
    return (acc);
}

References isalpha(), isdigit(), isspace(), isupper(), and LLONG_MIN.