pub unsafe extern "C" fn us_socket_context_on_writable(
ssl: c_int,
context: *mut us_socket_context_t,
on_writable: Option<unsafe extern "C" fn(s: *mut us_socket_t) -> *mut us_socket_t>
)pub unsafe extern "C" fn us_socket_context_on_writable(
ssl: c_int,
context: *mut us_socket_context_t,
on_writable: Option<unsafe extern "C" fn(s: *mut us_socket_t) -> *mut us_socket_t>
)