1// Copyright (C) 2018 The Android Open Source Project
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//      http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15import {assertExists, assertTrue} from './logging';
16import {Engine, LoadingTracker} from './engine';
17
18let bundlePath: string;
19let idleWasmWorker: Worker;
20let activeWasmWorker: Worker;
21
22export function initWasm(root: string) {
23  bundlePath = root + 'engine_bundle.js';
24  idleWasmWorker = new Worker(bundlePath);
25}
26
27// This method is called trace_controller whenever a new trace is loaded.
28export function resetEngineWorker(): MessagePort {
29  const channel = new MessageChannel();
30  const port = channel.port1;
31
32  // We keep always an idle worker around, the first one is created by the
33  // main() below, so we can hide the latency of the Wasm initialization.
34  if (activeWasmWorker !== undefined) {
35    activeWasmWorker.terminate();
36  }
37
38  // Swap the active worker with the idle one and create a new idle worker
39  // for the next trace.
40  activeWasmWorker = assertExists(idleWasmWorker);
41  activeWasmWorker.postMessage(port, [port]);
42  idleWasmWorker = new Worker(bundlePath);
43  return channel.port2;
44}
45
46/**
47 * This implementation of Engine uses a WASM backend hosted in a separate
48 * worker thread.
49 */
50export class WasmEngineProxy extends Engine {
51  readonly id: string;
52  private port: MessagePort;
53
54  constructor(id: string, port: MessagePort, loadingTracker?: LoadingTracker) {
55    super(loadingTracker);
56    this.id = id;
57    this.port = port;
58    this.port.onmessage = this.onMessage.bind(this);
59  }
60
61  onMessage(m: MessageEvent) {
62    assertTrue(m.data instanceof Uint8Array);
63    super.onRpcResponseBytes(m.data as Uint8Array);
64  }
65
66  rpcSendRequestBytes(data: Uint8Array): void {
67    // We deliberately don't use a transfer list because protobufjs reuses the
68    // same buffer when encoding messages (which is good, because creating a new
69    // TypedArray for each decode operation would be too expensive).
70    this.port.postMessage(data);
71  }
72}
73