init

Skeletal actor framework. Somewhat unweildy, needs a message box, a better runtime, and different channels. However, hello world example works

.gitignore

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+/target

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Cargo.toml

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+[package]
+name = "swactor"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+
+[dependencies]
+tokio = { version = "1.48.0", features = ["rt", "macros"] }
+tokio-util = "0.7.17"

README.md

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+# about
+Small wasm-compatible actor library

examples/hello.rs

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+use swactor::Actor;
+use tokio::sync::oneshot;
+
+pub enum GreeterMessage {
+    Name(String),
+}
+
+pub enum GreeterResponse {
+    Hello(String),
+}
+
+pub struct Greeter;
+
+impl Actor for Greeter {
+    type Message = GreeterMessage;
+    type Response = GreeterResponse;
+
+    fn handle_message(&self, msg: Self::Message, tx: oneshot::Sender<Self::Response>) {
+        let rep = match msg {
+            GreeterMessage::Name(name) => GreeterResponse::Hello(format!("Hello, {name}!")),
+        };
+
+        if let Err(_) = tx.send(rep) {
+            // Greeter is not responsible for a dropped Receiver
+        }
+    }
+}
+
+fn main() {
+    let rt = tokio::runtime::Builder::new_current_thread()
+        .build()
+        .expect("failed to build runtime");
+    let greeter = Greeter::spawn(Greeter, &rt);
+
+    let response = rt
+        .block_on(async move {
+            greeter
+                .send(GreeterMessage::Name("world".to_string()))
+                .await
+        })
+        .expect("failed to get respose");
+
+    match response {
+        GreeterResponse::Hello(hello) => println!("{hello}"),
+    }
+}

src/error.rs

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+pub type Error = Box<dyn std::error::Error + Send + Sync + 'static>;
+pub type Result<T> = std::result::Result<T, Error>;
+pub fn convert_err<E: std::fmt::Debug>(e: E) -> Error {
+    format!("{e:?}").into()
+}

src/lib.rs

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+pub mod error;
+
+/// Public export as the oneshot channel is in the `Actor` trait signature
+pub use tokio::sync::oneshot;
+
+use tokio::{
+    sync::{mpsc},
+    task::JoinHandle,
+};
+use tokio_util::sync::CancellationToken;
+
+use crate::error::{Result, convert_err};
+
+
+const DEFAULT_CHANNEL_SIZE: usize = 100;
+
+/// Combined 'JoinHandle' to await the actor process and 'Sender' for communication
+pub struct Handle<A>
+where
+    A: Actor,
+{
+    cancel_token: CancellationToken,
+    tx: mpsc::Sender<(A::Message, oneshot::Sender<A::Response>)>,
+    _handle: JoinHandle<Result<()>>,
+    // to prevent accidental swaps, strongly type the handle
+    _type: std::marker::PhantomData<A>,
+}
+
+impl<A: Actor> Handle<A> {
+
+    /// Send a message to the spawned `Actor` task and get a response corresponding to the `Actor::Response` type
+    pub async fn send(&self, msg: A::Message) -> Result<A::Response> {
+        let (tx, rx) = oneshot::channel::<A::Response>();
+        self.tx.send((msg, tx)).await.map_err(convert_err)?;
+
+        rx.await.map_err(convert_err)
+    }
+}
+
+impl<A: Actor> Drop for Handle<A> {
+    fn drop(&mut self) {
+        self.cancel_token.cancel();
+    }
+}
+
+/// Primary trait defining an `Actor` capable of receiving, processing, and transmitting messages
+pub trait Actor: Send + Sized + Unpin + 'static {
+    /// The type for messages received by this `Actor`
+    type Message: Send;
+    /// The type for responses given by this actor when called from `Handle::send(..)`
+    type Response: Send;
+
+    /// Inner method that defines actor behavior
+    fn handle_message(&self, msg: Self::Message, tx: oneshot::Sender<Self::Response>);
+
+    /// Spawns the `Actor` utilizing the given runtime context
+    /// Only `tokio` runtime is accepted for now
+    fn spawn(self, ctx: &tokio::runtime::Runtime) -> Handle<Self> {
+        let cancel_token = CancellationToken::new();
+        let cancel = cancel_token.clone();
+
+        let (tx, mut rx) =
+            mpsc::channel::<(Self::Message, oneshot::Sender<Self::Response>)>(DEFAULT_CHANNEL_SIZE);
+        let handle = ctx.spawn(async move {
+            let mut res = Ok(());
+            loop {
+                tokio::select! {
+                    _ = cancel.cancelled() => {
+                        break;
+                    },
+
+                    msg = rx.recv() => {
+                        match msg {
+                            Some(m) => { self.handle_message(m.0, m.1); },
+                            None => {res = Err(format!("Sender handle was dropped without calling cancel!").into()); break; },
+                        }
+                    }
+                };
+            }
+
+            res
+        });
+
+        Handle {
+            cancel_token,
+            _handle: handle,
+            tx,
+            _type: std::marker::PhantomData::<Self>,
+        }
+    }
+}