68 lines
1.3 KiB
TypeScript
68 lines
1.3 KiB
TypeScript
// Copyright 2021 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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const SECOND = 1000;
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export const FIBONACCI_TIMEOUTS: ReadonlyArray<number> = [
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1 * SECOND,
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2 * SECOND,
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3 * SECOND,
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5 * SECOND,
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8 * SECOND,
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13 * SECOND,
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21 * SECOND,
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34 * SECOND,
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55 * SECOND,
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];
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export type BackOffOptionsType = Readonly<{
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jitter?: number;
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// Testing
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random?: () => number;
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}>;
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const DEFAULT_RANDOM = () => Math.random();
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export class BackOff {
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private count = 0;
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constructor(
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private readonly timeouts: ReadonlyArray<number>,
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private readonly options: BackOffOptionsType = {}
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) {}
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public get(): number {
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let result = this.timeouts[this.count];
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const { jitter = 0, random = DEFAULT_RANDOM } = this.options;
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// Do not apply jitter larger than the timeout value. It is supposed to be
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// activated for longer timeouts.
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if (jitter < result) {
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result += random() * jitter;
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}
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return result;
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}
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public getAndIncrement(): number {
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const result = this.get();
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if (!this.isFull()) {
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this.count += 1;
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}
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return result;
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}
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public reset(): void {
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this.count = 0;
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}
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public isFull(): boolean {
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return this.count === this.timeouts.length - 1;
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}
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public getIndex(): number {
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return this.count;
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}
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}
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