dst

    A pointer to the destination array containing the resulting
    sequence of wide-character codes.

 src

    An address of the pointer to an array containing a sequence of
    multibyte characters to be converted.

 len

    The maximum number of wide character codes that can be stored in
    the array pointed to by dst.

 ps

    A pointer to the mbstate_t object. If a NULL pointer is
    specified, the function uses its internal mbstate_t object.
    mbstate_t is an opaque datatype intended to keep the conversion
    state for the state-dependent codesets.