Merge commit 'be3e8236086165e5e45a5a10783823874b3f3ebd' as 'lib/vscode'

lib/vscode/src/vs/base/common/cancellation.ts

@@ -0,0 +1,144 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { Emitter, Event } from 'vs/base/common/event';
+import { IDisposable } from 'vs/base/common/lifecycle';
+
+export interface CancellationToken {
+
+	/**
+	 * A flag signalling is cancellation has been requested.
+	 */
+	readonly isCancellationRequested: boolean;
+
+	/**
+	 * An event which fires when cancellation is requested. This event
+	 * only ever fires `once` as cancellation can only happen once. Listeners
+	 * that are registered after cancellation will be called (next event loop run),
+	 * but also only once.
+	 *
+	 * @event
+	 */
+	readonly onCancellationRequested: (listener: (e: any) => any, thisArgs?: any, disposables?: IDisposable[]) => IDisposable;
+}
+
+const shortcutEvent: Event<any> = Object.freeze(function (callback, context?): IDisposable {
+	const handle = setTimeout(callback.bind(context), 0);
+	return { dispose() { clearTimeout(handle); } };
+});
+
+export namespace CancellationToken {
+
+	export function isCancellationToken(thing: unknown): thing is CancellationToken {
+		if (thing === CancellationToken.None || thing === CancellationToken.Cancelled) {
+			return true;
+		}
+		if (thing instanceof MutableToken) {
+			return true;
+		}
+		if (!thing || typeof thing !== 'object') {
+			return false;
+		}
+		return typeof (thing as CancellationToken).isCancellationRequested === 'boolean'
+			&& typeof (thing as CancellationToken).onCancellationRequested === 'function';
+	}
+
+
+	export const None: CancellationToken = Object.freeze({
+		isCancellationRequested: false,
+		onCancellationRequested: Event.None
+	});
+
+	export const Cancelled: CancellationToken = Object.freeze({
+		isCancellationRequested: true,
+		onCancellationRequested: shortcutEvent
+	});
+}
+
+class MutableToken implements CancellationToken {
+
+	private _isCancelled: boolean = false;
+	private _emitter: Emitter<any> | null = null;
+
+	public cancel() {
+		if (!this._isCancelled) {
+			this._isCancelled = true;
+			if (this._emitter) {
+				this._emitter.fire(undefined);
+				this.dispose();
+			}
+		}
+	}
+
+	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;
+	}
+
+	public dispose(): void {
+		if (this._emitter) {
+			this._emitter.dispose();
+			this._emitter = null;
+		}
+	}
+}
+
+export class CancellationTokenSource {
+
+	private _token?: CancellationToken = undefined;
+	private _parentListener?: IDisposable = undefined;
+
+	constructor(parent?: CancellationToken) {
+		this._parentListener = parent && parent.onCancellationRequested(this.cancel, this);
+	}
+
+	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 if (this._token instanceof MutableToken) {
+			// actually cancel
+			this._token.cancel();
+		}
+	}
+
+	dispose(cancel: boolean = false): void {
+		if (cancel) {
+			this.cancel();
+		}
+		if (this._parentListener) {
+			this._parentListener.dispose();
+		}
+		if (!this._token) {
+			// ensure to initialize with an empty token if we had none
+			this._token = CancellationToken.None;
+
+		} else if (this._token instanceof MutableToken) {
+			// actually dispose
+			this._token.dispose();
+		}
+	}
+}