Function libcoap_sys::coap_pdu_encode_header

pub unsafe extern "C" fn coap_pdu_encode_header(
    pdu: *mut coap_pdu_t, 
    proto: coap_proto_t
) -> usize

Compose the protocol specific header for the specified PDU. @param pdu A newly composed PDU. @param proto The target wire protocol. @return Number of header bytes prepended before pdu->token or 0 on error.