6 files changed, 483 insertions, 0 deletions
diff --git a/extensions/broadcast_channel/01_broadcast_channel.js b/extensions/broadcast_channel/01_broadcast_channel.js
new file mode 100644
index 000000000..7670b0cfd
--- /dev/null
+++ b/extensions/broadcast_channel/01_broadcast_channel.js
@@ -0,0 +1,167 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+"use strict";
+
+((window) => {
+  const core = window.Deno.core;
+  const webidl = window.__bootstrap.webidl;
+  const { setTarget } = window.__bootstrap.event;
+
+  const handlerSymbol = Symbol("eventHandlers");
+  function makeWrappedHandler(handler) {
+    function wrappedHandler(...args) {
+      if (typeof wrappedHandler.handler !== "function") {
+        return;
+      }
+      return wrappedHandler.handler.call(this, ...args);
+    }
+    wrappedHandler.handler = handler;
+    return wrappedHandler;
+  }
+  // TODO(lucacasonato) reuse when we can reuse code between web crates
+  function defineEventHandler(emitter, name) {
+    // HTML specification section 8.1.5.1
+    Object.defineProperty(emitter, `on${name}`, {
+      get() {
+        // TODO(bnoordhuis) The "BroadcastChannel should have an onmessage
+        // event" WPT test expects that .onmessage !== undefined. Returning
+        // null makes it pass but is perhaps not exactly in the spirit.
+        return this[handlerSymbol]?.get(name)?.handler ?? null;
+      },
+      set(value) {
+        if (!this[handlerSymbol]) {
+          this[handlerSymbol] = new Map();
+        }
+        let handlerWrapper = this[handlerSymbol]?.get(name);
+        if (handlerWrapper) {
+          handlerWrapper.handler = value;
+        } else {
+          handlerWrapper = makeWrappedHandler(value);
+          this.addEventListener(name, handlerWrapper);
+        }
+        this[handlerSymbol].set(name, handlerWrapper);
+      },
+      configurable: true,
+      enumerable: true,
+    });
+  }
+
+  const _name = Symbol("[[name]]");
+  const _closed = Symbol("[[closed]]");
+
+  const channels = [];
+  let rid = null;
+
+  async function recv() {
+    while (channels.length > 0) {
+      const message = await core.opAsync("op_broadcast_recv", rid);
+
+      if (message === null) {
+        break;
+      }
+
+      const [name, data] = message;
+      dispatch(null, name, new Uint8Array(data));
+    }
+
+    core.close(rid);
+    rid = null;
+  }
+
+  function dispatch(source, name, data) {
+    for (const channel of channels) {
+      if (channel === source) continue; // Don't self-send.
+      if (channel[_name] !== name) continue;
+      if (channel[_closed]) continue;
+
+      const go = () => {
+        if (channel[_closed]) return;
+        const event = new MessageEvent("message", {
+          data: core.deserialize(data), // TODO(bnoordhuis) Cache immutables.
+          origin: "http://127.0.0.1",
+        });
+        setTarget(event, channel);
+        channel.dispatchEvent(event);
+      };
+
+      defer(go);
+    }
+  }
+
+  // Defer to avoid starving the event loop. Not using queueMicrotask()
+  // for that reason: it lets promises make forward progress but can
+  // still starve other parts of the event loop.
+  function defer(go) {
+    setTimeout(go, 1);
+  }
+
+  class BroadcastChannel extends EventTarget {
+    [_name];
+    [_closed] = false;
+
+    get name() {
+      return this[_name];
+    }
+
+    constructor(name) {
+      super();
+
+      const prefix = "Failed to construct 'broadcastChannel'";
+      webidl.requiredArguments(arguments.length, 1, { prefix });
+
+      this[_name] = webidl.converters["DOMString"](name, {
+        prefix,
+        context: "Argument 1",
+      });
+
+      this[webidl.brand] = webidl.brand;
+
+      channels.push(this);
+
+      if (rid === null) {
+        // Create the rid immediately, otherwise there is a time window (and a
+        // race condition) where messages can get lost, because recv() is async.
+        rid = core.opSync("op_broadcast_subscribe");
+        recv();
+      }
+    }
+
+    postMessage(message) {
+      webidl.assertBranded(this, BroadcastChannel);
+
+      const prefix = "Failed to execute 'postMessage' on 'BroadcastChannel'";
+      webidl.requiredArguments(arguments.length, 1, { prefix });
+
+      if (this[_closed]) {
+        throw new DOMException("Already closed", "InvalidStateError");
+      }
+
+      if (typeof message === "function" || typeof message === "symbol") {
+        throw new DOMException("Uncloneable value", "DataCloneError");
+      }
+
+      const data = core.serialize(message);
+
+      // Send to other listeners in this VM.
+      dispatch(this, this[_name], new Uint8Array(data));
+
+      // Send to listeners in other VMs.
+      defer(() => core.opAsync("op_broadcast_send", [rid, this[_name]], data));
+    }
+
+    close() {
+      webidl.assertBranded(this, BroadcastChannel);
+      this[_closed] = true;
+
+      const index = channels.indexOf(this);
+      if (index === -1) return;
+
+      channels.splice(index, 1);
+      if (channels.length === 0) core.opSync("op_broadcast_unsubscribe", rid);
+    }
+  }
+
+  defineEventHandler(BroadcastChannel.prototype, "message");
+  defineEventHandler(BroadcastChannel.prototype, "messageerror");
+
+  window.__bootstrap.broadcastChannel = { BroadcastChannel };
+})(this);
diff --git a/extensions/broadcast_channel/Cargo.toml b/extensions/broadcast_channel/Cargo.toml
new file mode 100644
index 000000000..7bc65f3a0
--- /dev/null
+++ b/extensions/broadcast_channel/Cargo.toml
@@ -0,0 +1,20 @@
+# Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+[package]
+name = "deno_broadcast_channel"
+version = "0.1.0"
+edition = "2018"
+description = "Implementation of BroadcastChannel API for Deno"
+authors = ["the Deno authors"]
+license = "MIT"
+readme = "README.md"
+repository = "https://github.com/denoland/deno"
+
+[lib]
+path = "lib.rs"
+
+[dependencies]
+async-trait = "0.1"
+deno_core = { version = "0.88.0", path = "../../core" }
+tokio = { version = "1.4.0", features = ["full"] }
+uuid = { version = "0.8.2", features = ["v4"] }
diff --git a/extensions/broadcast_channel/README.md b/extensions/broadcast_channel/README.md
new file mode 100644
index 000000000..5b5034ef7
--- /dev/null
+++ b/extensions/broadcast_channel/README.md
@@ -0,0 +1,5 @@
+# deno_broadcast_channel
+
+This crate implements the BroadcastChannel functions of Deno.
+
+Spec: https://html.spec.whatwg.org/multipage/web-messaging.html
diff --git a/extensions/broadcast_channel/in_memory_broadcast_channel.rs b/extensions/broadcast_channel/in_memory_broadcast_channel.rs
new file mode 100644
index 000000000..34498c830
--- /dev/null
+++ b/extensions/broadcast_channel/in_memory_broadcast_channel.rs
@@ -0,0 +1,97 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+use crate::BroadcastChannel;
+use async_trait::async_trait;
+use deno_core::error::AnyError;
+use std::sync::Arc;
+use std::sync::Mutex;
+use tokio::sync::broadcast;
+use tokio::sync::mpsc;
+use uuid::Uuid;
+
+#[derive(Clone)]
+pub struct InMemoryBroadcastChannel(Arc<Mutex<broadcast::Sender<Message>>>);
+
+pub struct InMemoryBroadcastChannelResource {
+  rx: tokio::sync::Mutex<(
+    broadcast::Receiver<Message>,
+    mpsc::UnboundedReceiver<()>,
+  )>,
+  cancel_tx: mpsc::UnboundedSender<()>,
+  uuid: Uuid,
+}
+
+#[derive(Clone, Debug)]
+struct Message {
+  name: Arc<String>,
+  data: Arc<Vec<u8>>,
+  uuid: Uuid,
+}
+
+impl Default for InMemoryBroadcastChannel {
+  fn default() -> Self {
+    let (tx, _) = broadcast::channel(256);
+    Self(Arc::new(Mutex::new(tx)))
+  }
+}
+
+#[async_trait]
+impl BroadcastChannel for InMemoryBroadcastChannel {
+  type Resource = InMemoryBroadcastChannelResource;
+
+  fn subscribe(&self) -> Result<Self::Resource, AnyError> {
+    let (cancel_tx, cancel_rx) = mpsc::unbounded_channel();
+    let broadcast_rx = self.0.lock().unwrap().subscribe();
+    let rx = tokio::sync::Mutex::new((broadcast_rx, cancel_rx));
+    let uuid = Uuid::new_v4();
+    Ok(Self::Resource {
+      rx,
+      cancel_tx,
+      uuid,
+    })
+  }
+
+  fn unsubscribe(&self, resource: &Self::Resource) -> Result<(), AnyError> {
+    Ok(resource.cancel_tx.send(())?)
+  }
+
+  async fn send(
+    &self,
+    resource: &Self::Resource,
+    name: String,
+    data: Vec<u8>,
+  ) -> Result<(), AnyError> {
+    let name = Arc::new(name);
+    let data = Arc::new(data);
+    let uuid = resource.uuid;
+    self.0.lock().unwrap().send(Message { name, data, uuid })?;
+    Ok(())
+  }
+
+  async fn recv(
+    &self,
+    resource: &Self::Resource,
+  ) -> Result<Option<crate::Message>, AnyError> {
+    let mut g = resource.rx.lock().await;
+    let (broadcast_rx, cancel_rx) = &mut *g;
+    loop {
+      let result = tokio::select! {
+        r = broadcast_rx.recv() => r,
+        _ = cancel_rx.recv() => return Ok(None),
+      };
+      use tokio::sync::broadcast::error::RecvError::*;
+      match result {
+        Err(Closed) => return Ok(None),
+        Err(Lagged(_)) => (), // Backlogged, messages dropped.
+        Ok(message) if message.uuid == resource.uuid => (), // Self-send.
+        Ok(message) => {
+          let name = String::clone(&message.name);
+          let data = Vec::clone(&message.data);
+          return Ok(Some((name, data)));
+        }
+      }
+    }
+  }
+}
+
+impl deno_core::Resource for InMemoryBroadcastChannelResource {}
diff --git a/extensions/broadcast_channel/lib.deno_broadcast_channel.d.ts b/extensions/broadcast_channel/lib.deno_broadcast_channel.d.ts
new file mode 100644
index 000000000..c8efef778
--- /dev/null
+++ b/extensions/broadcast_channel/lib.deno_broadcast_channel.d.ts
@@ -0,0 +1,55 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+// deno-lint-ignore-file no-explicit-any
+
+/// <reference no-default-lib="true" />
+/// <reference lib="esnext" />
+
+interface BroadcastChannelEventMap {
+  "message": MessageEvent;
+  "messageerror": MessageEvent;
+}
+
+interface BroadcastChannel extends EventTarget {
+  /**
+   * Returns the channel name (as passed to the constructor).
+   */
+  readonly name: string;
+  onmessage: ((this: BroadcastChannel, ev: MessageEvent) => any) | null;
+  onmessageerror: ((this: BroadcastChannel, ev: MessageEvent) => any) | null;
+  /**
+   * Closes the BroadcastChannel object, opening it up to garbage collection.
+   */
+  close(): void;
+  /**
+   * Sends the given message to other BroadcastChannel objects set up for
+   * this channel. Messages can be structured objects, e.g. nested objects
+   * and arrays.
+   */
+  postMessage(message: any): void;
+  addEventListener<K extends keyof BroadcastChannelEventMap>(
+    type: K,
+    listener: (this: BroadcastChannel, ev: BroadcastChannelEventMap[K]) => any,
+    options?: boolean | AddEventListenerOptions,
+  ): void;
+  addEventListener(
+    type: string,
+    listener: EventListenerOrEventListenerObject,
+    options?: boolean | AddEventListenerOptions,
+  ): void;
+  removeEventListener<K extends keyof BroadcastChannelEventMap>(
+    type: K,
+    listener: (this: BroadcastChannel, ev: BroadcastChannelEventMap[K]) => any,
+    options?: boolean | EventListenerOptions,
+  ): void;
+  removeEventListener(
+    type: string,
+    listener: EventListenerOrEventListenerObject,
+    options?: boolean | EventListenerOptions,
+  ): void;
+}
+
+declare var BroadcastChannel: {
+  prototype: BroadcastChannel;
+  new (name: string): BroadcastChannel;
+};
diff --git a/extensions/broadcast_channel/lib.rs b/extensions/broadcast_channel/lib.rs
new file mode 100644
index 000000000..b2a79916c
--- /dev/null
+++ b/extensions/broadcast_channel/lib.rs
@@ -0,0 +1,139 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+mod in_memory_broadcast_channel;
+
+pub use in_memory_broadcast_channel::InMemoryBroadcastChannel;
+
+use async_trait::async_trait;
+use deno_core::error::bad_resource_id;
+use deno_core::error::AnyError;
+use deno_core::include_js_files;
+use deno_core::op_async;
+use deno_core::op_sync;
+use deno_core::Extension;
+use deno_core::OpState;
+use deno_core::Resource;
+use deno_core::ResourceId;
+use deno_core::ZeroCopyBuf;
+use std::cell::RefCell;
+use std::path::PathBuf;
+use std::rc::Rc;
+
+#[async_trait]
+pub trait BroadcastChannel: Clone {
+  type Resource: Resource;
+
+  fn subscribe(&self) -> Result<Self::Resource, AnyError>;
+
+  fn unsubscribe(&self, resource: &Self::Resource) -> Result<(), AnyError>;
+
+  async fn send(
+    &self,
+    resource: &Self::Resource,
+    name: String,
+    data: Vec<u8>,
+  ) -> Result<(), AnyError>;
+
+  async fn recv(
+    &self,
+    resource: &Self::Resource,
+  ) -> Result<Option<Message>, AnyError>;
+}
+
+pub type Message = (String, Vec<u8>);
+
+struct Unstable(bool); // --unstable
+
+pub fn op_broadcast_subscribe<BC: BroadcastChannel + 'static>(
+  state: &mut OpState,
+  _args: (),
+  _buf: (),
+) -> Result<ResourceId, AnyError> {
+  let unstable = state.borrow::<Unstable>().0;
+
+  if !unstable {
+    eprintln!(
+      "Unstable API 'BroadcastChannel'. The --unstable flag must be provided.",
+    );
+    std::process::exit(70);
+  }
+
+  let bc = state.borrow::<BC>();
+  let resource = bc.subscribe()?;
+  Ok(state.resource_table.add(resource))
+}
+
+pub fn op_broadcast_unsubscribe<BC: BroadcastChannel + 'static>(
+  state: &mut OpState,
+  rid: ResourceId,
+  _buf: (),
+) -> Result<(), AnyError> {
+  let resource = state
+    .resource_table
+    .get::<BC::Resource>(rid)
+    .ok_or_else(bad_resource_id)?;
+  let bc = state.borrow::<BC>();
+  bc.unsubscribe(&resource)
+}
+
+pub async fn op_broadcast_send<BC: BroadcastChannel + 'static>(
+  state: Rc<RefCell<OpState>>,
+  (rid, name): (ResourceId, String),
+  buf: ZeroCopyBuf,
+) -> Result<(), AnyError> {
+  let resource = state
+    .borrow()
+    .resource_table
+    .get::<BC::Resource>(rid)
+    .ok_or_else(bad_resource_id)?;
+  let bc = state.borrow().borrow::<BC>().clone();
+  bc.send(&resource, name, buf.to_vec()).await
+}
+
+pub async fn op_broadcast_recv<BC: BroadcastChannel + 'static>(
+  state: Rc<RefCell<OpState>>,
+  rid: ResourceId,
+  _buf: (),
+) -> Result<Option<Message>, AnyError> {
+  let resource = state
+    .borrow()
+    .resource_table
+    .get::<BC::Resource>(rid)
+    .ok_or_else(bad_resource_id)?;
+  let bc = state.borrow().borrow::<BC>().clone();
+  bc.recv(&resource).await
+}
+
+pub fn init<BC: BroadcastChannel + 'static>(
+  bc: BC,
+  unstable: bool,
+) -> Extension {
+  Extension::builder()
+    .js(include_js_files!(
+      prefix "deno:extensions/broadcast_channel",
+      "01_broadcast_channel.js",
+    ))
+    .ops(vec![
+      (
+        "op_broadcast_subscribe",
+        op_sync(op_broadcast_subscribe::<BC>),
+      ),
+      (
+        "op_broadcast_unsubscribe",
+        op_sync(op_broadcast_unsubscribe::<BC>),
+      ),
+      ("op_broadcast_send", op_async(op_broadcast_send::<BC>)),
+      ("op_broadcast_recv", op_async(op_broadcast_recv::<BC>)),
+    ])
+    .state(move |state| {
+      state.put(bc.clone());
+      state.put(Unstable(unstable));
+      Ok(())
+    })
+    .build()
+}
+
+pub fn get_declaration() -> PathBuf {
+  PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+    .join("lib.deno_broadcast_channel.d.ts")
+}