| |
The wcstoul() function converts the initial portion of the wide character string pointed to by nptr to unsigned long int representation.
It first decomposes the input wide-character string into three parts: an initial, possibly empty, sequence of white-space wide-character codes (as specified by the function iswspace(3C)); a subject sequence interpreted as an integer represented in some radix determined by the value of base; and a final wide-character string of one or more unrecognized wide character codes, including the terminating null wide-character code of the input wide character string. It then attempts
to convert the subject sequence to an unsigned integer, and returns 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.
In other than the POSIX locale, additional subject sequence forms may be accepted.
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.
Because 0 and ULONG_MAX are returned on error and 0 is also a valid return on success, an application wishing to check for error situations should set errno to 0, call wcstoul(), then check errno and if it is non-zero, assume an error has occurred.
|
