Module protocol 

PostgreSQL v3 wire protocol message framing (Phase 3.1 PG parity).

Implements the bits of the PG v3 protocol RedDB needs for simple query support: startup negotiation, authentication (trust), the simple query flow (Q → T/D*/C/Z), and error reporting.

The full PG reference lives at: https://www.postgresql.org/docs/current/protocol-message-formats.html

Frame format (v3)

After the startup message, every frame is:

[u8 type] [i32 length (includes itself)] [payload]

Frames are big-endian. We use tokio::io::AsyncRead/Write so the listener can plug into the same task model as the existing wire binary protocol.

Structs

ColumnDescriptor

StartupParams

Enums

BackendMessage

Backend (server → client) messages we emit.

FrontendMessage

Frontend (client → server) messages we parse.

PgWireError

Error type surfaced by the framing layer. Wraps IO errors plus structural validation failures (bad message tag, truncated frame).

TransactionStatus

Constants

PG_CANCEL_REQUEST

PG_GSSENC_REQUEST

PG_PROTOCOL_V3

Protocol version constant: 3.0 → 196608 (major<<16 | minor).

PG_SSL_REQUEST

Special startup-phase requests that share the StartupMessage length header. The PG reference calls out three: SSLRequest (80877103), GSSENCRequest (80877104), CancelRequest (80877102).

Functions

read_frame

Read a regular tagged frame after the startup handshake.

read_startup

Read the initial StartupMessage (or SSL/GSS request). The startup frame has no type byte — just a length prefix followed by the payload. Returns either a decoded Startup/SSL/GSS message or an error.

write_frame

Serialize + send a backend message.

write_raw_byte

Emit a raw byte (used for the SSL/GSS negotiation response: ‘N’ meaning “not supported, continue in plaintext”).