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Diffstat (limited to 'packages')
-rw-r--r-- | packages/taler-util/src/promises.ts | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/packages/taler-util/src/promises.ts b/packages/taler-util/src/promises.ts new file mode 100644 index 000000000..bc1e40260 --- /dev/null +++ b/packages/taler-util/src/promises.ts @@ -0,0 +1,112 @@ +/* + 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; + } +} |