Offload some more waveform processing onto a worker (#9223)

src/WorkerManager.ts

@@ -0,0 +1,46 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { defer, IDeferred } from "matrix-js-sdk/src/utils";
+
+import { WorkerPayload } from "./workers/worker";
+
+export class WorkerManager<Request extends {}, Response> {
+    private readonly worker: Worker;
+    private seq = 0;
+    private pendingDeferredMap = new Map<number, IDeferred<Response>>();
+
+    public constructor(WorkerConstructor: { new (): Worker }) {
+        this.worker = new WorkerConstructor();
+        this.worker.onmessage = this.onMessage;
+    }
+
+    private onMessage = (ev: MessageEvent<Response & WorkerPayload>): void => {
+        const deferred = this.pendingDeferredMap.get(ev.data.seq);
+        if (deferred) {
+            this.pendingDeferredMap.delete(ev.data.seq);
+            deferred.resolve(ev.data);
+        }
+    };
+
+    public call(request: Request): Promise<Response> {
+        const seq = this.seq++;
+        const deferred = defer<Response>();
+        this.pendingDeferredMap.set(seq, deferred);
+        this.worker.postMessage({ seq, ...request });
+        return deferred.promise;
+    }
+}