Source: lib/util/mutex.js

  1. /*! @license
  2.  * Shaka Player
  3.  * Copyright 2016 Google LLC
  4.  * SPDX-License-Identifier: Apache-2.0
  5.  */
  7. goog.provide('shaka.util.Mutex');
  9. goog.require('shaka.log');
  12. /**
  13.  * @summary A simple mutex.
  14.  */
  15. shaka.util.Mutex = class {
  16.   /** Constructs the mutex. */
  17.   constructor() {
  18.     /** @private {?string} */
  19.     this.acquiredIdentifier = null;
  21.     /** @private {!Array.<function()>} */
  22.     this.unlockQueue = [];
  23.   }
  25.   /**
  26.    * Acquires the mutex, as soon as possible.
  27.    * @param {string} identifier
  28.    * @return {!Promise}
  29.    */
  30.   async acquire(identifier) {
  31.     shaka.log.v2(identifier + ' has requested mutex');
  32.     if (this.acquiredIdentifier) {
  33.       await new Promise((resolve) => this.unlockQueue.push(resolve));
  34.     }
  35.     this.acquiredIdentifier = identifier;
  36.     shaka.log.v2(identifier + ' has acquired mutex');
  37.   }
  39.   /**
  40.    * Releases your hold on the mutex.
  41.    */
  42.   release() {
  43.     shaka.log.v2(this.acquiredIdentifier + ' has released mutex');
  44.     if (this.unlockQueue.length > 0) {
  45.       this.unlockQueue.shift()();
  46.     } else {
  47.       this.acquiredIdentifier = null;
  48.     }
  49.   }
  51.   /**
  52.    * Completely releases the mutex. Meant for use by the tests.
  53.    */
  54.   releaseAll() {
  55.     while (this.acquiredIdentifier) {
  56.       this.release();
  57.     }
  58.   }
  59. };