strtoull.c File Reference

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

Include dependency graph for strtoull.c:

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Functions
unsigned long long	strtoull (const char *__restrict nptr, char **__restrict endptr, int base)
	Interprets an unsigned long long value in a byte string pointed to by str. More...

Function Documentation

strtoull()

unsigned long long strtoull	(	const char *__restrict	str,
		char **__restrict	str_end,
		int	base
	)

Interprets an unsigned long long value in a byte string pointed to by str.

Interprets an unsigned long long value in a byte string pointed to by str. Discards any whitespace characters (as identified by calling

See also

isspace()) until the first non-whitespace character is found, then takes as many characters as possible to form a valid base-n (where n=base) long number representation and converts them to an unsigned long long value. The valid long value consists of the following parts:

 1) (optional) plus or minus sign
 2) (optional) prefix (0) indicating octal base (applies only when the base is 8 or ​0​)
 3) (optional) prefix (0x or 0X) indicating hexadecimal base (applies only when the base is

16 or ​0​) 4) a sequence of digits

The set of valid values for base is {0,2,3,...,36}. The set of valid digits for base-2 integers is {0,1}, for base-3 integers is {0,1,2}, and so on. For bases larger than 10, valid digits include alphabetic characters, starting from Aa for base-11 integer, to Zz for base-36 integer. The case of the characters is ignored.

If the value of base is ​0​, the numeric base is auto-detected: if the prefix is 0, the base is octal, if the prefix is 0x or 0X, the base is hexadecimal, otherwise the base is decimal.

If the minus sign was part of the input sequence, the numeric value calculated from the sequence of digits is negated as if by unary minus in the result type.

If the str is empty or does not have the expected form, no conversion is performed, and (if str_end is not NULL) the value of str is stored in the object pointed to by str_end.

Parameters

str	pointer to the null-terminated byte string to be interpreted
str_end	pointer to a pointer to character.
base	base of the interpreted integer value

Returns

returns the result of the conversion, unless the value would underflow or overflow. If the converted value falls out of range of corresponding return type, a range error occurs (setting errno to ERANGE) and LONG_MAX, LONG_MIN, LLONG_MAX or LLONG_MIN is returned. If no conversion can be performed, ​0​ is returned.

Definition at line 44 of file strtoull.c.

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

    /*
     * See strtoq for comments as to the logic used.
     */
    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;
        }
    }

    cutoff = ULLONG_MAX / (unsigned long long)base;
    cutlim = (int)(ULLONG_MAX % (unsigned long long)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 *= (unsigned long)base;
            acc += (unsigned long)c;
        }
    }
    if(any < 0)
    {
        acc = ULLONG_MAX;
        // errno = ERANGE;
    }
    else if(!any)
    {
    noconv:
        // PJ: nonstandard, but since no errno, acc = 0
        acc = 0;
        // errno = EINVAL;
    }
    else if(neg)
    {
        acc = -acc;
    }
    if(endptr != NULL)
    {
        *endptr = (char*)(uintptr_t)(any ? s - 1 : nptr);
    }
    return (acc);
}

References isspace(), NULL, and ULLONG_MAX.