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/*
This file is part of GNU Taler
(C) 2019 GNUnet e.V.
TALER is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 3, or (at your option) any later version.
TALER is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
TALER; see the file COPYING. If not, see <http://www.gnu.org/licenses/>
*/
/**
* An opened promise.
*
* @see {@link openPromise}
*/
export interface OpenedPromise<T> {
promise: Promise<T>;
resolve: (val: T) => void;
reject: (err: any) => void;
lastError?: any;
}
/**
* Get an unresolved promise together with its extracted resolve / reject
* function.
*
* Recent ECMAScript proposals also call this a promise capability.
*/
export function openPromise<T>(): OpenedPromise<T> {
let resolve: ((x?: any) => void) | null = null;
let promiseReject: ((reason?: any) => void) | null = null;
const promise = new Promise<T>((res, rej) => {
resolve = res;
promiseReject = rej;
});
if (!(resolve && promiseReject)) {
// Never happens, unless JS implementation is broken
throw Error("JS implementation is broken");
}
const result: OpenedPromise<T> = { resolve, reject: promiseReject, promise };
function saveLastError(reason?: any) {
result.lastError = reason;
promiseReject!(reason);
}
result.reject = saveLastError;
return result;
}
export class AsyncCondition {
private promCap?: OpenedPromise<void> = undefined;
constructor() {}
wait(): Promise<void> {
if (!this.promCap) {
this.promCap = openPromise<void>();
}
return this.promCap.promise;
}
trigger(): void {
if (this.promCap) {
this.promCap.resolve();
}
this.promCap = undefined;
}
}
/**
* Flag that can be raised to notify asynchronous waiters.
*
* You can think of it as a promise that can
* be un-resolved.
*/
export class AsyncFlag {
private promCap?: OpenedPromise<void> = undefined;
private internalFlagRaised: boolean = false;
constructor() {}
/**
* Wait until the flag is raised.
*
* Reset if before returning.
*/
wait(): Promise<void> {
if (this.internalFlagRaised) {
return Promise.resolve();
}
if (!this.promCap) {
this.promCap = openPromise<void>();
}
return this.promCap.promise;
}
raise(): void {
this.internalFlagRaised = true;
if (this.promCap) {
this.promCap.resolve();
}
}
reset(): void {
this.internalFlagRaised = false;
this.promCap = undefined;
}
}
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