Function async_coap::message::codec::encode_option_without_value

pub fn encode_option_without_value(
    buffer: &mut [u8], 
    prev_key: OptionNumber, 
    key: OptionNumber, 
    value_len: usize
) -> Result<usize, Error>

Encodes all parts of an option into the given buffer except the value. All other parts, including the value length, are encoded. This is typically used directly when inserting options, otherwise encode_option() (which writes the value) is typically a better fit.