repe-rs

Rust implementation of the REPE RPC protocol, focused on JSON as the body format.

Spec reference: https://github.com/beve-org/beve
Crate: repe on crates.io

This crate provides:

REPE header and message types with correct little-endian encoding
Message encode/decode to/from bytes and I/O helpers for streams
JSON body helpers using serde/serde_json
Error codes and formats aligned with the spec

Installation

Add to your Cargo.toml:

[dependencies]
repe = "0.1.1"

Quick start

use repe::{Message, QueryFormat, BodyFormat};

// Build a JSON message
let msg = Message::builder()
    .id(42)
    .query_str("/status")
    .query_format(QueryFormat::JsonPointer)
    .body_json(&serde_json::json!({"ping": true}))?
    .build();

// Serialize to bytes and back
let bytes = msg.to_vec();
let parsed = repe::Message::from_slice(&bytes)?;

assert_eq!(parsed.header.id, 42);
assert_eq!(parsed.header.body_format, BodyFormat::Json as u16);
let val: serde_json::Value = parsed.json_body()?;
assert_eq!(val["ping"], true);

Examples

examples/json_roundtrip.rs – construct/serialize/parse a JSON message.
examples/server.rs – run a JSON-pointer server (TCP).
examples/client.rs – call the server routes.
examples/async_server.rs – tokio-based async server.
examples/async_client.rs – tokio-based async client.

Notes

Only JSON, UTF-8 (for error messages), and raw bytes helpers are implemented. BEVE is intentionally not implemented.
The header reserved field is currently ignored (per spec receivers must not reject non-zero values).
The header length is validated to be 48 + query_length + body_length.

JSON Pointer Routing and Typed Handlers

Router keys are JSON Pointer paths (e.g., /ping, /echo, /status). Raw-binary queries are rejected with an explicit Invalid query error.
Add JSON Value handlers with .with("/path", |v: serde_json::Value| -> Result<Value, (ErrorCode,String)>).
Add typed handlers with .with_typed("/path", |req: T| -> Result<R, (ErrorCode,String)>) where T: Deserialize, R: Serialize.
- Typed handlers auto-deserialize JSON bodies into T and serialize R to JSON responses.
- If a non-JSON body is sent to a typed/JSON handler, the server returns Invalid body.
Implement the pluggable trait JsonTypedHandler to attach methods from a service type:

use repe::{Router, JsonTypedHandler, ErrorCode};
use serde::{Deserialize, Serialize};

#[derive(Deserialize)]
struct Input { name: String }
#[derive(Serialize)]
struct Output { greeting: String }

struct Greeter;
impl JsonTypedHandler for Greeter {
    type In = Input;
    type Out = Output;
    fn call(&self, input: Self::In) -> Result<Self::Out, (ErrorCode, String)> {
        Ok(Output { greeting: format!("Hello, {}!", input.name) })
    }
}

let router = Router::new().with_handler("/greet", Greeter);

Async (tokio)

Use AsyncServer and AsyncClient for asynchronous operation with tokio.
See examples/async_server.rs and examples/async_client.rs.

Server

Build a router and serve TCP:

use repe::{Router, Server};
use serde_json::json;
use std::time::Duration;

let router = Router::new()
    .with("/ping", |_v| Ok(json!({"pong": true})))
    .with("/echo", |v| Ok(json!({"echo": v})))
    .with("/status", |_v| Ok(json!({"status": "ok"})));

let server = Server::new(router)
    .read_timeout(Some(Duration::from_secs(120)))
    .write_timeout(Some(Duration::from_secs(120)));
let listener = server.listen("127.0.0.1:8081")?;
server.serve(listener)?;

Client

Connect and call JSON-pointer routes with JSON bodies:

use repe::Client;
use serde_json::json;

let mut client = Client::connect("127.0.0.1:8081")?;
let pong = client.call_json("/ping", &json!({}))?;
assert_eq!(pong["pong"], true);

Notify semantics

If a request is marked notify = true, the server will process the handler but will not send a response.
In the protocol, the id still increments client-side, but no matching response should be expected.
The Client::notify_json and AsyncClient::notify_json helpers set the flag accordingly.

Error handling

Errors are returned “in-band” as responses with ec != Ok and a UTF‑8 body describing the error.
Common mappings:
- Header parse/validation issues → InvalidHeader or ParseError.
- JSON deserialization/serialization issues → ParseError.
- Missing routes → MethodNotFound with the requested path in the message.
- Application failures from handlers → return (ErrorCode, String) to control both fields.
Clients also surface mismatched response IDs as RepeError::ResponseIdMismatch and mismatched protocol versions as RepeError::VersionMismatch.

Async usage (minimal end‑to‑end)

use repe::{Router, AsyncServer, AsyncClient};
use serde_json::json;

# #[tokio::main]
# async fn main() -> std::io::Result<()> {
let router = Router::new().with_json("/ping", |_v| Ok(json!({"pong": true})));
let listener = AsyncServer::listen(("127.0.0.1", 0)).await?;
let addr = listener.local_addr()?;
tokio::spawn(async move { let _ = AsyncServer::new(router).serve(listener).await; });

let mut client = AsyncClient::connect(addr).await.unwrap();
let pong = client.call_json("/ping", &json!({})).await.unwrap();
assert_eq!(pong["pong"], true);
# Ok(()) }

Running the examples

cargo run --example server
cargo run --example client
cargo run --example async_server
cargo run --example async_client

Design overview

Fixed header size is 48 bytes (HEADER_SIZE) followed by query and body payloads.
All numeric fields are little‑endian. Header length equals 48 + query_length + body_length and is validated.
query_format/body_format use the enums in repe::constants.
Suggested query format is JSON Pointer (/path/to/resource).

JSON Pointer helpers

parse_json_pointer splits a pointer into unescaped tokens.
eval_json_pointer indexes into a serde_json::Value using array indices or object keys.

Testing

Run cargo test to execute unit and integration tests. The crate denies warnings and includes async tests; you’ll need a recent tokio.
Example integration tests cover sync/async server + client calls, unknown routes, handler error mapping, ID mismatches, and timeouts.

License

MIT, see LICENSE.

repe 0.1.2

repe-rs