| // Copyright 2014 The Closure Library Authors. All Rights Reserved. |
| // |
| // Licensed 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 CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| /** |
| * @fileoverview Common code for weak collections. |
| * |
| * The helpers in this file are used for the shim implementations of |
| * {@code goog.structs.weak.Map} and {@code goog.structs.weak.Set}, for browsers |
| * that do not support ECMAScript 6 native WeakMap and WeakSet. |
| * |
| * IMPORTANT CAVEAT: On browsers that do not provide native WeakMap and WeakSet |
| * implementations, these data structure are only partially weak, and CAN LEAK |
| * MEMORY. Specifically, if a key is no longer held, the key-value pair (in the |
| * case of Map) and some internal metadata (in the case of Set), can be garbage |
| * collected; however, if a key is still held when a Map or Set is no longer |
| * held, the value and metadata will not be collected. |
| * |
| * RECOMMENDATIONS: If the lifetime of the weak collection is expected to be |
| * shorter than that of its keys, the keys should be explicitly removed from the |
| * collection when they are disposed. If this is not possible, this library may |
| * be inappopriate for the application. |
| * |
| * BROWSER COMPATIBILITY: This library is compatible with browsers with a |
| * correct implementation of Object.defineProperty (IE9+, FF4+, SF5.1+, CH5+, |
| * OP12+, etc). |
| * @see goog.structs.weak.SUPPORTED_BROWSER |
| * @see http://kangax.github.io/compat-table/es5/#Object.defineProperty |
| * |
| * @package |
| */ |
| |
| |
| goog.provide('goog.structs.weak'); |
| |
| goog.require('goog.userAgent'); |
| |
| |
| /** |
| * Whether this browser supports weak collections, using either the native or |
| * shim implementation. |
| * @const |
| */ |
| // Only test for shim, since ES6 native WeakMap/Set imply ES5 shim dependencies |
| goog.structs.weak.SUPPORTED_BROWSER = Object.defineProperty && |
| // IE<9 and Safari<5.1 cannot defineProperty on some objects |
| !(goog.userAgent.IE && !goog.userAgent.isVersionOrHigher('9')) && |
| !(goog.userAgent.SAFARI && !goog.userAgent.isVersionOrHigher('534.48.3')); |
| |
| |
| /** |
| * Whether to use the browser's native WeakMap. |
| * @const |
| */ |
| goog.structs.weak.USE_NATIVE_WEAKMAP = 'WeakMap' in goog.global && |
| // Firefox<24 WeakMap disallows some objects as keys |
| // See https://github.com/Polymer/WeakMap/issues/3 |
| !(goog.userAgent.GECKO && !goog.userAgent.isVersionOrHigher('24')); |
| |
| |
| /** |
| * Whether to use the browser's native WeakSet. |
| * @const |
| */ |
| goog.structs.weak.USE_NATIVE_WEAKSET = 'WeakSet' in goog.global; |
| |
| |
| /** @const */ |
| goog.structs.weak.WEAKREFS_PROPERTY_NAME = '__shimWeakrefs__'; |
| |
| |
| /** |
| * Counter used to generate unique ID for shim. |
| * @private |
| */ |
| goog.structs.weak.counter_ = 0; |
| |
| |
| /** |
| * Generate a unique ID for shim. |
| * @return {string} |
| */ |
| goog.structs.weak.generateId = function() { |
| return (Math.random() * 1e9 >>> 0) + '' + |
| (goog.structs.weak.counter_++ % 1e9); |
| }; |
| |
| |
| /** |
| * Checks that the key is an extensible object, otherwise throws an Error. |
| * @param {*} key The key. |
| */ |
| goog.structs.weak.checkKeyType = function(key) { |
| if (!goog.isObject(key)) { |
| throw TypeError('Invalid value used in weak collection'); |
| } |
| if (Object.isExtensible && !Object.isExtensible(key)) { |
| throw TypeError('Unsupported non-extensible object used as weak map key'); |
| } |
| }; |
| |
| |
| /** |
| * Adds a key-value pair to the collection with the given ID. Helper for shim |
| * implementations of Map#set and Set#add. |
| * @param {string} id The unique ID of the shim weak collection. |
| * @param {*} key The key. |
| * @param {*} value value to add. |
| */ |
| goog.structs.weak.set = function(id, key, value) { |
| goog.structs.weak.checkKeyType(key); |
| if (!key.hasOwnProperty(goog.structs.weak.WEAKREFS_PROPERTY_NAME)) { |
| // Use defineProperty to make property non-enumerable |
| Object.defineProperty(/** @type {!Object} */(key), |
| goog.structs.weak.WEAKREFS_PROPERTY_NAME, {value: {}}); |
| } |
| key[goog.structs.weak.WEAKREFS_PROPERTY_NAME][id] = value; |
| }; |
| |
| |
| /** |
| * Returns whether the collection with the given ID contains the given |
| * key. Helper for shim implementations of Map#containsKey and Set#contains. |
| * @param {string} id The unique ID of the shim weak collection. |
| * @param {*} key The key to check for. |
| * @return {boolean} |
| */ |
| goog.structs.weak.has = function(id, key) { |
| goog.structs.weak.checkKeyType(key); |
| return key.hasOwnProperty(goog.structs.weak.WEAKREFS_PROPERTY_NAME) ? |
| id in key[goog.structs.weak.WEAKREFS_PROPERTY_NAME] : |
| false; |
| }; |
| |
| |
| /** |
| * Removes a key-value pair based on the key. Helper for shim implementations of |
| * Map#remove and Set#remove. |
| * @param {string} id The unique ID of the shim weak collection. |
| * @param {*} key The key to remove. |
| * @return {boolean} Whether object was removed. |
| */ |
| goog.structs.weak.remove = function(id, key) { |
| if (goog.structs.weak.has(id, key)) { |
| delete key[goog.structs.weak.WEAKREFS_PROPERTY_NAME][id]; |
| return true; |
| } |
| return false; |
| }; |