pub type PFN_CRYPT_ASYNC_PARAM_FREE_FUNC = Option<unsafe extern "C" fn(pszParamOid: LPSTR, pvParam: LPVOID)>;
enum PFN_CRYPT_ASYNC_PARAM_FREE_FUNC { None, Some(unsafe extern "C" fn(_: *mut i8, _: *mut c_void)), }
No value.
Some value of type T.
T