on input, length of input array with Unicode code points,
on exit, length of output array with Unicode code points.
size_t maxucs4len
maximum length of input/output array.
Stringprep_profile_flags flags
a Stringprep_profile_flags value, or 0.
const Stringprep_profile * profile
pointer to Stringprep_profile to use.
DESCRIPTION
Prepare the input UCS-4 string according to the stringprep profile,
and write back the result to the input string.
The input is not required to be zero terminated (ucs4[len] = 0).
The output will not be zero terminated unless ucs4[len] = 0.
Instead, see stringprep_4zi() if your input is zero terminated or
if you want the output to be.
Since the stringprep operation can expand the string, maxucs4len
indicate how large the buffer holding the string is. This function
will not read or write to code points outside that size.
The flags are one of Stringprep_profile_flags values, or 0.
The profile contain the Stringprep_profile instructions to
perform. Your application can define new profiles, possibly
re-using the generic stringprep tables that always will be part of
the library, or use one of the currently supported profiles.
RETURN VALUE
Returns STRINGPREP_OK iff successful, or an
Stringprep_rc error code.
