feat: connection handshake — Client::connect / Server::serve_handshaked - #8
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Before any calls, each end declares { ir_hash, wire_format, framing,
capabilities } and refuses on a mismatch -- catches "one end msgpack, one
end JSON" and two ends built from different schema versions.
- contract::Handshake -- lifetime-free, Copy. wire_format / framing are
carried as name_hash (FNV-1a) of a *name*, not a numeric id: a user's
add-on WireFormat picks a namespaced name and its hash won't collide
with a built-in, no central registry. Fixed 31-byte frame
([magic][ver][ir_hash u64][wire_format u64][framing u64][caps u32]).
Handshake::new(ir_hash, wire_format_name, framing_name, caps) hashes.
- WireFormat::name() -> &'static str (was going to be id() -> u16;
dropped). MsgPack -> "msgpack". contract::FRAMING_DATAGRAM.
- RuntimeError::Handshake (non_exhaustive, so additive).
- Client::connect(transport, format, local) -> Result<Self, _> and
Server::serve_handshaked(transport, local): send ours, read + check the
peer's, then proceed. Client::new / Server::serve are unchanged and
skip it entirely -- "misaligned mode", documented, for legacy peers.
- BufMut::put_u32_le.
tests/handshake_roundtrip.rs: matching handshakes connect + a call goes
through; a schema-hash mismatch is refused before any call (both ends);
misaligned mode skips it. Plus handshake.rs unit tests. All feature
configs green.
Generated code supplies IR_HASH and calls Client::connect -- a follow-up
codegen PR.
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Before any calls, each end declares
{ ir_hash, wire_format, framing, capabilities }and refuses on a mismatch — catches "one end MessagePack, one end JSON" and two ends built from different schema versions (§4.6).contract::HandshakeLifetime-free,
Copy.wire_format/framingare carried asname_hash(FNV-1a) of a name, not a numeric id — a user's add-onWireFormatpicks a namespaced name ("com.acme.myformat") and its hash won't collide with a built-in; no central id registry. Fixed 31-byte frame:[magic:2][ver:1][ir_hash:u64][wire_format:u64][framing:u64][caps:u32].Handshake::new(ir_hash, wire_format_name, framing_name, caps)does the hashing.WireFormat::name() -> &'static str(MsgPack→"msgpack");contract::FRAMING_DATAGRAM.RuntimeError::Handshake(the enum is#[non_exhaustive], so additive).The two modes
Client::connect(t, fmt, local) -> Result<Self, _>/Server::serve_handshaked(t, local)checkthe peer's, then proceedClient::new/Server::servecheckrefuses onir_hash/wire_format/framingdisagreement; capability bits may differ.Tests
tests/handshake_roundtrip.rs— matching handshakes connect and a call goes through; a schema-hash mismatch is refused before any call (both ends getRuntimeError::Handshake); misaligned mode skips it. Plushandshake.rsunit tests (encode/decode round-trip,name_hashdeterminism, truncated/foreign rejection). All feature configs green; no new clippy warnings.Next
A codegen PR: the generator emits
IR_HASH(from the frozen IR fingerprint) and a<Proto>Client::connect/<Proto>Dispatcherserve helper that fills in theHandshake.