Module frame 

4-byte big-endian length-prefixed framing.

A frame is a 4-byte big-endian unsigned length followed by exactly that many payload bytes. This is the framing used by three contracts:

• MAVLink socket: payload is one raw MAVLink frame, max 65536, zero-length permitted (the Python server only checks the upper bound).
• plugin RPC socket: payload is a msgpack envelope, max 4 MiB, zero-length rejected (the Python reader treats length == 0 as a protocol error).
• state socket v2: payload is a msgpack state snapshot.

The reject-zero behaviour differs per contract, so decode_len takes it as an argument rather than baking in one policy.

Enums

FrameError

Constants

HEADER_SIZE

Size of the length prefix in bytes.

MAVLINK_MAX_FRAME

Maximum MAVLink frame payload (Contract A: MAX_FRAME_SIZE).

PLUGIN_MAX_FRAME

Maximum plugin RPC envelope payload (Contract C: MAX_FRAME_BYTES).

Functions

decode_len

Decode the payload length from a 4-byte big-endian header.

encode_frame

Encode a payload as a length-prefixed frame: 4-byte big-endian length followed by the payload. Returns an error if the payload exceeds max or cannot be represented in a u32 length.