#include <wchar.h>

unsigned long wcstoul(const wchar_t *restrict nptr,
 wchar_t **restrict endptr, int base);

unsigned long long wcstoull(const wchar_t *restrict nptr,
 wchar_t **restrict endptr, int base);

The wcstoul() and wcstoull() functions convert the initial portion of the wide-character string pointed to by nptr to unsigned long and unsigned long long representation, respectively. First they decompose the input wide-character string into three parts:

They then attempt to convert the subject sequence to an unsigned integer and return the result.

If the value of base is 0, the expected form of the subject sequence is that of a decimal constant, an octal constant, or a hexadecimal constant, any of which may be preceded by a `+' or a `-' sign. A decimal constant begins with a non-zero digit, and consists of a sequence of decimal digits. An octal constant consists of the prefix `0', optionally followed by a sequence of the digits `0' to `7' only. A hexadecimal constant consists of the prefix `0x' or `0X', followed by a sequence of the decimal digits and letters `a' (or `A') to `f' (or `F'), with values 10 to 15, respectively.

If the value of base is between 2 and 36, the expected form of the subject sequence is a sequence of letters and digits representing an integer with the radix specified by base, optionally preceded by a `+' or a `-' sign, but not including an integer suffix. The letters from `a' (or `A') to `z' (or `Z') inclusive are ascribed the values 10 to 35; only letters whose ascribed values are less than that of base are permitted. If the value of base is 16, the wide-character codes `0x' or `0X' may optionally precede the sequence of letters and digits, following the sign, if present.

The subject sequence is defined as the longest initial subsequence of the input wide-character string, starting with the first wide-character code that is not a white space and is of the expected form. The subject sequence contains no wide-character codes if the input wide-character string is empty or consists entirely of white-space wide-character codes, or if the first wide-character code that is not a white space is other than a sign or a permissible letter or digit.

If the subject sequence has the expected form and the value of base is 0, the sequence of wide-character codes starting with the first digit is interpreted as an integer constant. If the subject sequence has the expected form and the value of base is between 2 and 36, it is used as the base for conversion, ascribing to each letter its value as given above. If the subject sequence begins with a minus sign, the value resulting from the conversion is negated. A pointer to the final wide character string is stored in the object pointed to by endptr, provided that endptr is not a null pointer.

If the subject sequence is empty or does not have the expected form, no conversion is performed; the value of nptr is stored in the object pointed to by endptr, provided that endptr is not a null pointer.

The wcstoul() function does not change the setting of errno if successful.

Since 0, {ULONG_MAX}, and {ULLONG_MAX} are returned on error and 0 is also a valid return on success, an application wanting to check for error situations should set errno to 0, then call wcstoul() or wcstoull(), then check errno.

The wcstoul() and wcstoull() functions do not change the setting of errno if successful.

Upon successful completion, wcstoul() and wcstoull() return the converted value, if any. If no conversion could be performed, 0 is returned and errno may be set to indicate the error. If the correct value is outside the range of representable values, {ULONG_MAX} or {ULLONG_MAX}, respectively, is returned and errno is set to ERANGE.

The wcstoul() and wcstoull() functions will fail if: EINVAL

The wcstoul() and wcstoull() functions may fail if: EINVAL

Unlike wcstod(3C) and wcstol(3C), wcstoul() and wcstoull() must always return a non-negative number; using the return value of wcstoul() for out-of-range numbers with wcstoul() or wcstoull() could cause more severe problems than just loss of precision if those numbers can ever be negative.

See attributes(5) for descriptions of the following attributes:

isspace(3C), iswalpha(3C), scanf(3C), wcstod(3C), wcstol(3C), attributes(5), standards(5)