Write normal game-message and ACK packet framing directly into bounded stack spans, hash fragments without materialization, and send the populated slice to the socket. Preserve exact wire bytes and ISAAC failure ordering with differential and zero-allocation tests.
Completes the encode side of the codec so acdream can stop hand-
assembling outbound packets in tests. Given a PacketHeader (with Flags
set, DataSize ignored/overwritten) and a body byte span, Encode:
1. Overwrites header.DataSize with body.Length
2. Parses the optional section out of the body (reusing
PacketHeaderOptional.Parse as a length measurer) and hashes those bytes
3. If BlobFragments is set, walks the body tail as back-to-back
fragments and sums their Hash32s
4. For unencrypted: header.Checksum = headerHash + optionalHash + fragmentHash
5. For EncryptedChecksum: pulls one ISAAC keystream word and computes
header.Checksum = headerHash + (isaacKey XOR payloadHash)
6. Packs header + body into the final datagram
Tests (6 new, 67 total in net project, 144 across both test projects):
- Unencrypted round-trip: Encode then TryDecode recovers the AckSequence
field
- DataSize is overwritten (caller can pass garbage)
- Encrypted round-trip: two ISAACs with same seed, one encoding and
one decoding, both agree on the keystream word
- Encrypted but no ISAAC → throws InvalidOperationException
- LoginRequest end-to-end: LoginRequest.Build → Encode → TryDecode →
LoginRequest.Parse round-trips credentials exactly. This is the
single most important integration test for the outbound side —
every byte this exercises is exactly what acdream will put on the
wire when Phase 4.6 goes live.
- BlobFragments body with one embedded fragment: Encode preserves
the fragment and fragmentHash is correctly folded into the checksum
Codec is now complete end-to-end (decode + encode) and has the
LoginRequest outbound path proven against its own decoder. The next
commit will wire NetClient over real UDP sockets and connect to the
localhost ACE server.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
