68 lines
2.2 KiB
JavaScript
68 lines
2.2 KiB
JavaScript
"use strict";
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/**
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* Copyright 2023 Google LLC.
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* Copyright (c) Microsoft Corporation.
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* Copyright 2022 The Chromium Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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Object.defineProperty(exports, "__esModule", { value: true });
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exports.Mutex = void 0;
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/**
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* Use Mutex class to coordinate local concurrent operations.
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* Once `acquire` promise resolves, you hold the lock and must
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* call `release` function returned by `acquire` to release the
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* lock. Failing to `release` the lock may lead to deadlocks.
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*/
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class Mutex {
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#locked = false;
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#acquirers = [];
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// This is FIFO.
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acquire() {
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const state = { resolved: false };
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if (this.#locked) {
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return new Promise((resolve) => {
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this.#acquirers.push(() => resolve(this.#release.bind(this, state)));
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});
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}
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this.#locked = true;
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return Promise.resolve(this.#release.bind(this, state));
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}
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#release(state) {
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if (state.resolved) {
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throw new Error('Cannot release more than once.');
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}
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state.resolved = true;
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const resolve = this.#acquirers.shift();
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if (!resolve) {
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this.#locked = false;
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return;
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}
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resolve();
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}
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async run(action) {
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const release = await this.acquire();
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try {
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// Note we need to await here because we want the await to release AFTER
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// that await happens. Returning action() will trigger the release
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// immediately which is counter to what we want.
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const result = await action();
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return result;
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}
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finally {
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release();
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}
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}
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}
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exports.Mutex = Mutex;
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//# sourceMappingURL=Mutex.js.map
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