un-get wide character from input
function pushes the wide character wc (converted to a
wchar_t) back onto the input stream pointed to by
stream. The pushed-backed wide characters will be
returned by subsequent reads on the stream (in reverse order). A successful
intervening call, using the same stream, to one of the file positioning
rewind(3) will discard the pushed back wide characters.
One wide character of push-back is guaranteed, but as long as there is sufficient memory, an effectively infinite amount of pushback is allowed.
If a character is successfully pushed back, the end-of-file indicator for the stream is cleared.
ungetwc() function returns the wide
character pushed back after the conversion, or
if the operation fails. If the value of the argument c
WEOF, the operation will fail and
the stream will remain unchanged.
fseek(3), getwc(3), ungetc(3)
ungetwc() function conforms to
The current implementation uses a fixed sized ungetwc-buffer.