SQL Operations Studio Public Preview 1 (0.23) release source code

dataprotocol-node/jsonrpc/src/cancellation.ts

@@ -0,0 +1,97 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+'use strict';
+
+import { Event, Emitter } from './events';
+
+export interface CancellationToken {
+	/**
+	 * Is `true` when the token has been cancelled, `false` otherwise.
+	 */
+	isCancellationRequested: boolean;
+
+	/**
+	 * An [event](#Event) which fires upon cancellation.
+	 */
+	onCancellationRequested: Event<any>;
+}
+
+export namespace CancellationToken {
+
+	export const None: CancellationToken = Object.freeze({
+		isCancellationRequested: false,
+		onCancellationRequested: Event.None
+	});
+
+	export const Cancelled: CancellationToken = Object.freeze({
+		isCancellationRequested: true,
+		onCancellationRequested: Event.None
+	});
+}
+
+const shortcutEvent: Event<any> = Object.freeze(function (callback, context?) {
+	let handle = setTimeout(callback.bind(context), 0);
+	return { dispose() { clearTimeout(handle); } };
+});
+
+class MutableToken implements CancellationToken {
+
+	private _isCancelled: boolean = false;
+	private _emitter: Emitter<any>;
+
+	public cancel() {
+		if (!this._isCancelled) {
+			this._isCancelled = true;
+			if (this._emitter) {
+				this._emitter.fire(undefined);
+				this._emitter = undefined;
+			}
+		}
+	}
+
+	get isCancellationRequested(): boolean {
+		return this._isCancelled;
+	}
+
+	get onCancellationRequested(): Event<any> {
+		if (this._isCancelled) {
+			return shortcutEvent;
+		}
+		if (!this._emitter) {
+			this._emitter = new Emitter<any>();
+		}
+		return this._emitter.event;
+	}
+}
+
+export class CancellationTokenSource {
+
+	private _token: CancellationToken;
+
+	get token(): CancellationToken {
+		if (!this._token) {
+			// be lazy and create the token only when
+			// actually needed
+			this._token = new MutableToken();
+		}
+		return this._token;
+	}
+
+	cancel(): void {
+		if (!this._token) {
+			// save an object by returning the default
+			// cancelled token when cancellation happens
+			// before someone asks for the token
+			this._token = CancellationToken.Cancelled;
+		} else {
+			(<MutableToken>this._token).cancel();
+		}
+	}
+
+	dispose(): void {
+		this.cancel();
+	}
+}