1 files changed, 117 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..34f8b9e19
--- /dev/null
+++ b/extensions/broadcast_channel/01_broadcast_channel.js
@@ -0,0 +1,117 @@
+// 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 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() {
+        return this[handlerSymbol]?.get(name)?.handler;
+      },
+      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 _rid = Symbol("[[rid]]");
+
+  class BroadcastChannel extends EventTarget {
+    [_name];
+    [_closed] = false;
+    [_rid];
+
+    get name() {
+      return this[_name];
+    }
+
+    constructor(name) {
+      super();
+
+      window.location;
+
+      const prefix = "Failed to construct 'broadcastChannel'";
+      webidl.requiredArguments(arguments.length, 1, { prefix });
+
+      this[_name] = webidl.converters["DOMString"](name, {
+        prefix,
+        context: "Argument 1",
+      });
+
+      this[_rid] = core.opSync("op_broadcast_open", this[_name]);
+
+      this[webidl.brand] = webidl.brand;
+
+      this.#eventLoop();
+    }
+
+    postMessage(message) {
+      webidl.assertBranded(this, BroadcastChannel);
+
+      if (this[_closed]) {
+        throw new DOMException("Already closed", "InvalidStateError");
+      }
+
+      core.opAsync("op_broadcast_send", this[_rid], core.serialize(message));
+    }
+
+    close() {
+      webidl.assertBranded(this, BroadcastChannel);
+
+      this[_closed] = true;
+      core.close(this[_rid]);
+    }
+
+    async #eventLoop() {
+      while (!this[_closed]) {
+        const message = await core.opAsync(
+          "op_broadcast_next_event",
+          this[_rid],
+        );
+
+        if (message.length !== 0) {
+          const event = new MessageEvent("message", {
+            data: core.deserialize(message),
+            origin: window.location,
+          });
+          event.target = this;
+          this.dispatchEvent(event);
+        }
+      }
+    }
+  }
+
+  defineEventHandler(BroadcastChannel.prototype, "message");
+  defineEventHandler(BroadcastChannel.prototype, "messageerror");
+
+  window.__bootstrap.broadcastChannel = { BroadcastChannel };
+})(this);