| 1 | package types |
| 2 | |
| 3 | import ( |
| 4 | "encoding/binary" |
| 5 | "errors" |
| 6 | ) |
| 7 | |
| 8 | // errDatagramTooSmall is returned when a datagram payload is too short to |
| 9 | // contain a valid flow ID varint. |
| 10 | var errDatagramTooSmall = errors.New("datagram too small to decode") |
| 11 | |
| 12 | // DatagramFrame carries one relayed datagram. |
| 13 | // Wire encoding uses only FlowID and Payload with layout: |
| 14 | // [flowID varint][payload bytes] |
| 15 | type DatagramFrame struct { |
| 16 | FlowID uint32 |
| 17 | Payload []byte |
| 18 | Address string |
| 19 | RelayURL string |
| 20 | UDPAddr string |
| 21 | } |
| 22 | |
| 23 | // EncodeDatagram serialises a flow-framed datagram for transmission. |
| 24 | func EncodeDatagram(flowID uint32, payload []byte) []byte { |
| 25 | var buf [binary.MaxVarintLen32]byte |
| 26 | n := binary.PutUvarint(buf[:], uint64(flowID)) |
| 27 | out := make([]byte, n+len(payload)) |
| 28 | copy(out, buf[:n]) |
| 29 | copy(out[n:], payload) |
| 30 | return out |
| 31 | } |
| 32 | |
| 33 | // DecodeDatagram deserialises a flow-framed datagram. |
| 34 | func DecodeDatagram(data []byte) (DatagramFrame, error) { |
| 35 | flowID, n := binary.Uvarint(data) |
| 36 | if n <= 0 { |
| 37 | return DatagramFrame{}, errDatagramTooSmall |
| 38 | } |
| 39 | return DatagramFrame{ |
| 40 | FlowID: uint32(flowID), |
| 41 | Payload: data[n:], |
| 42 | }, nil |
| 43 | } |