1 files changed, 75 insertions, 0 deletions
diff --git a/packages/frontend/src/scripts/worker-multi-dispatch.ts b/packages/frontend/src/scripts/worker-multi-dispatch.ts
new file mode 100644
index 0000000000..1847a8ccff
--- /dev/null
+++ b/packages/frontend/src/scripts/worker-multi-dispatch.ts
@@ -0,0 +1,75 @@
+function defaultUseWorkerNumber(prev: number, totalWorkers: number) {
+    return prev + 1;
+}
+
+export class WorkerMultiDispatch<POST = any, RETURN = any> {
+    private symbol = Symbol('WorkerMultiDispatch');
+    private workers: Worker[] = [];
+    private terminated = false;
+    private prevWorkerNumber = 0;
+    private getUseWorkerNumber = defaultUseWorkerNumber;
+    private finalizationRegistry: FinalizationRegistry<symbol>;
+
+    constructor(workerConstructor: () => Worker, concurrency: number, getUseWorkerNumber = defaultUseWorkerNumber) {
+        this.getUseWorkerNumber = getUseWorkerNumber;
+        for (let i = 0; i < concurrency; i++) {
+            this.workers.push(workerConstructor());
+        }
+
+        this.finalizationRegistry = new FinalizationRegistry(() => {
+            this.terminate();
+        });
+        this.finalizationRegistry.register(this, this.symbol);
+
+        if (_DEV_) console.log('WorkerMultiDispatch: Created', this);
+    }
+
+    public postMessage(message: POST, options?: Transferable[] | StructuredSerializeOptions, useWorkerNumber: typeof defaultUseWorkerNumber = this.getUseWorkerNumber) {
+        let workerNumber = useWorkerNumber(this.prevWorkerNumber, this.workers.length);
+        workerNumber = Math.abs(Math.round(workerNumber)) % this.workers.length;
+        if (_DEV_) console.log('WorkerMultiDispatch: Posting message to worker', workerNumber, useWorkerNumber);
+        this.prevWorkerNumber = workerNumber;
+
+        // 不毛だがunionをoverloadに突っ込めない
+        // https://stackoverflow.com/questions/66507585/overload-signatures-union-types-and-no-overload-matches-this-call-error
+        // https://github.com/microsoft/TypeScript/issues/14107
+        if (Array.isArray(options)) {
+            this.workers[workerNumber].postMessage(message, options);
+        } else {
+            this.workers[workerNumber].postMessage(message, options);
+        }
+        return workerNumber;
+    }
+
+    public addListener(callback: (this: Worker, ev: MessageEvent<RETURN>) => any, options?: boolean | AddEventListenerOptions) {
+        this.workers.forEach(worker => {
+            worker.addEventListener('message', callback, options);
+        });
+    }
+
+    public removeListener(callback: (this: Worker, ev: MessageEvent<RETURN>) => any, options?: boolean | AddEventListenerOptions) {
+        this.workers.forEach(worker => {
+            worker.removeEventListener('message', callback, options);
+        });
+    }
+
+    public terminate() {
+        this.terminated = true;
+        if (_DEV_) console.log('WorkerMultiDispatch: Terminating', this);
+        this.workers.forEach(worker => {
+            worker.terminate();
+        });
+        this.workers = [];
+        this.finalizationRegistry.unregister(this);
+    }
+
+    public isTerminated() {
+        return this.terminated;
+    }
+    public getWorkers() {
+        return this.workers;
+    }
+    public getSymbol() {
+        return this.symbol;
+    }
+}