size_t mbstowcs(schar_t *pwcs
const char *str
Converts the string of multibyte characters pointed to by the
argument str to the array pointed to by pwcs. It
stores no more than n values into the array. Conversion
stops when it reaches the null character or n values have
been stored. The null character is stored in the array as zero
but is not counted in the return value.
If an invalid multibyte character is reached, then the value
-1 is returned. Otherwise the number of values stored in the
array is returned not including the terminating zero character.