@adobe/fastly-native-promises/src/lock.js

/*
 * Copyright 2020 Adobe. All rights reserved.
 * This file is licensed to you under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License. You may obtain a copy
 * of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under
 * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
 * OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
/* eslint-env mocha */

class Lock {
  constructor() {
    this._acquired = false;
    this._waiting = [];
  }

  async acquire() {
    if (this._acquired) {
      return new Promise((resolve) => this._waiting.push(resolve));
    }

    this._acquired = true;
    return Promise.resolve();
  }

  release() {
    if (this._waiting.length > 0) {
      const resolve = this._waiting.shift();
      resolve();
    } else {
      this._acquired = false;
    }
  }
}

module.exports = { Lock };