Minimal Worker support (#1476)

This adds the ability to spawn additional Isolates from Rust and send
and receive messages from them. This is preliminary work to support
running the typescript compiler in a separate isolate and thus support
native ES modules. Ref #975.

2 files changed, 81 insertions, 0 deletions

diff --git a/js/globals.ts b/js/globals.ts
index 663215341..849d2bb3f 100644
--- a/js/globals.ts
+++ b/js/globals.ts
@@ -19,6 +19,7 @@ import * as textEncoding from "./text_encoding";
 import * as timers from "./timers";
 import * as url from "./url";
 import * as urlSearchParams from "./url_search_params";
+import * as workers from "./workers";
 
 // These imports are not exposed and therefore are fine to just import the
 // symbols required.
@@ -86,3 +87,8 @@ window.TextEncoder = textEncoding.TextEncoder;
 export type TextEncoder = textEncoding.TextEncoder;
 window.TextDecoder = textEncoding.TextDecoder;
 export type TextDecoder = textEncoding.TextDecoder;
+
+window.workerMain = workers.workerMain;
+// TODO These shouldn't be available in main isolate.
+window.postMessage = workers.postMessage;
+window.close = workers.workerClose;
diff --git a/js/workers.ts b/js/workers.ts
new file mode 100644
index 000000000..f7aa857fc
--- /dev/null
+++ b/js/workers.ts
@@ -0,0 +1,75 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import * as dispatch from "./dispatch";
+import { libdeno } from "./libdeno";
+import * as msg from "gen/msg_generated";
+import * as flatbuffers from "./flatbuffers";
+import { assert, log } from "./util";
+import { globalEval } from "./global_eval";
+
+export async function postMessage(data: Uint8Array): Promise<void> {
+  const builder = flatbuffers.createBuilder();
+  msg.WorkerPostMessage.startWorkerPostMessage(builder);
+  const inner = msg.WorkerPostMessage.endWorkerPostMessage(builder);
+  const baseRes = await dispatch.sendAsync(
+    builder,
+    msg.Any.WorkerPostMessage,
+    inner,
+    data
+  );
+  assert(baseRes != null);
+}
+
+export async function getMessage(): Promise<null | Uint8Array> {
+  log("getMessage");
+  const builder = flatbuffers.createBuilder();
+  msg.WorkerGetMessage.startWorkerGetMessage(builder);
+  const inner = msg.WorkerGetMessage.endWorkerGetMessage(builder);
+  const baseRes = await dispatch.sendAsync(
+    builder,
+    msg.Any.WorkerGetMessage,
+    inner
+  );
+  assert(baseRes != null);
+  assert(
+    msg.Any.WorkerGetMessageRes === baseRes!.innerType(),
+    `base.innerType() unexpectedly is ${baseRes!.innerType()}`
+  );
+  const res = new msg.WorkerGetMessageRes();
+  assert(baseRes!.inner(res) != null);
+
+  const dataArray = res.dataArray();
+  if (dataArray == null) {
+    return null;
+  } else {
+    return new Uint8Array(dataArray!);
+  }
+}
+
+let isClosing = false;
+
+export function workerClose(): void {
+  isClosing = true;
+}
+
+export async function workerMain() {
+  log("workerMain");
+  libdeno.recv(dispatch.handleAsyncMsgFromRust);
+
+  // TODO avoid using globalEval to get Window. But circular imports if getting
+  // it from globals.ts
+  const window = globalEval("this");
+
+  while (!isClosing) {
+    const data = await getMessage();
+    if (data == null) {
+      log("workerMain got null message. quitting.");
+      break;
+    }
+    if (window["onmessage"]) {
+      const event = { data };
+      window.onmessage(event);
+    } else {
+      break;
+    }
+  }
+}