Function coap_opt_add_opaque

pub unsafe extern "C" fn coap_opt_add_opaque(
    pkt: *mut coap_pkt_t,
    optnum: u16,
    val: *const c_void,
    val_len: size_t,
) -> ssize_t

@brief Encode the given buffer as an opaque data option into pkt

@post pkt.payload advanced to first byte after option(s) @post pkt.payload_len reduced by option(s) length

@param[in,out] pkt pkt referencing target buffer @param[in] optnum option number to use @param[in] val pointer to the value to be set @param[in] val_len length of val

@return number of bytes written to buffer @return <0 on error @return -ENOSPC if no available options