Function encode_request 

pub fn encode_request(
    request: RequestToEncode<'_>,
    hmac_key: Option<&[u8]>,
) -> Result<Vec<u8>>

Encodes an outbound request.

This is sender-side semantic construction: the variant determines the flags, so callers never assemble flag bits themselves.

hmac_key is authoritative. Some(key) sets FLAG_HMAC, reserves the 16-byte authentication field after the header, and signs the finished datagram; None produces an unauthenticated packet.

RequestToEncode::Echo requires the negotiated Params because the sender must build a datagram of the negotiated length with the payload at the negotiated offset. The receiving side needs no Params — see decode_request.

Errors

Returns ProtoError::PayloadTooLarge when an ECHO payload does not fit the negotiated length, and ProtoError::PacketLengthUnrepresentable when the negotiated length is positive and wider than usize. A negative negotiated length is not an error: see echo_packet_len, which floors it at the mandatory field block.

Example

use irtt_proto::{encode_request, Params, RequestToEncode};

// An unauthenticated ECHO probe. `params` supplies the negotiated length,
// which reserves four payload bytes beyond the 16-byte echo header.
let params = Params { length: 20, ..Params::default() };
let packet = encode_request(
    RequestToEncode::Echo {
        token: 0x1234_5678_9abc_def0,
        sequence: 7,
        params: &params,
        payload: &[1, 2, 3, 4],
    },
    None,
).unwrap();
assert_eq!(packet.len(), 20);