grip-control

A Rust library for working with the GRIP (Generic Realtime Intermediary Protocol) WebSocket-over-HTTP wire format, as used by Fastly Fanout and compatible proxies.

Overview

grip-control handles the two directions of GRIP WebSocket communication:

• Parsing — decode inbound WebSocket event frames arriving from a GRIP proxy
• Building — encode outbound control frames to send back through the proxy

Zero external dependencies. The parser borrows directly from the input bytes — no heap allocation for frame payloads.

Usage

Add to Cargo.toml:

[dependencies]
grip-control = "0.6"

Parsing inbound frames

use grip_control::parse::WebsocketEvent;

let body: &[u8] = /* request body from GRIP proxy */;

match WebsocketEvent::parse_frame(body)? {
    WebsocketEvent::Open => { /* new connection */ }
    WebsocketEvent::Text(data) => { /* UTF-8 message */ }
    WebsocketEvent::Binary(data) => { /* binary message */ }
    WebsocketEvent::Ping => { /* keep-alive */ }
    WebsocketEvent::Close(data) => { /* connection closing */ }
    WebsocketEvent::Disconnect => { /* proxy disconnect */ }
}

Building outbound frames

use grip_control::frames::{ws_sub, ws_unsub, ws_text, ws_control};

// Subscribe the connection to a channel
let frame = ws_sub("my-channel");

// Send a text message
let frame = ws_text("hello");

// Unsubscribe
let frame = ws_unsub("my-channel");

// Raw control frame (e.g. "keep-alive\r\n")
let frame = ws_control("keep-alive");

Wire format

Frames follow the GRIP WebSocket-over-HTTP encoding:

COMMAND [HEX_LEN]\r\n[BODY]\r\n

Channel subscription/unsubscription frames are JSON-encoded GRIP control messages wrapped in a TEXT frame:

TEXT <len>\r\nc:{"type":"subscribe","channel":"<ch>"}\r\n

License

Licensed under either of MIT or Apache-2.0 at your option.