protocol library

Protocol layer: wire-format constants, header calculations and the Magpie / Packet interfaces.

Import this facade when you only need the wire format primitives (constants, calculators, command values, interfaces), without the concrete packet classes. See docs/protocol.md for the wire format.

Classes

Command

Reserved system command values.

Magpie

Core message interface. Every packet on the wire is a Magpie. All properties are read-only.

Packet

A Magpie whose header-level flags (A/B/C/D/E) and the two lengths are visible; this is the shape MessagePacket implements.

Constants

ATTACHMENT_LENGTH → const int

Attachment length: HMAC-SHA256, 32 bytes.

MAGIC_CODE → const int

Magic Code: 'M', 'P', '\0', '\1' (Messaging Protocol v1).

MAX_HEADER_LENGTH → const int

Maximum header size (all optional fields present, E=4).

MAX_PAYLOAD_LENGTH → const int

Suggested payload cap on the sender side (bytes).

MIN_HEADER_LENGTH → const int

Fixed header size: magic(4) + type(1) + headerLen(1) + payloadLen(2).

MSS → const int

Max datagram size (IPv6 minimum MTU 1280 - 40 ipv6 header - 8 udp header) MSS hard cap: header + payload (+ attachment) <= 1232.

Functions

calcCmd(int command) → int

C flag: command == 0 => C=0 (plain DATA).

calcDsn(int sn) → int

D flag: sn == 0 => D=0 (system command).

calcExt(int count) → int

E width: count >= 65536 => 4; count >= 2 => 2; else 0.

calcHeaderLength({required int bid, required int cmd, required int dsn, required int ext}) → int

Header length: N = 8 + 8·B + 4·D + 2·E + 4·C.

calcType({required int ack, required int bid, required int cmd, required int dsn, required int ext}) → int

Compose the type byte: A(7) B(6) C(5) D(4) E(low 3 bits).