mirror of
https://github.com/shaka-project/shaka-player.git
synced 2026-06-26 17:46:26 +03:00
Jacob Trimble
55 lines
1.4 KiB
JavaScript
55 lines
1.4 KiB
JavaScript
/**
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* @license
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* Copyright 2016 Google Inc.
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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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goog.provide('shaka.util.Lazy');
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goog.require('goog.asserts');
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/**
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* @summary
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* This contains a single value that is lazily generated when it is first
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* requested. This can store any value except "undefined".
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*
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* @template T
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* @export
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*/
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shaka.util.Lazy = class {
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/** @param {function():T} gen */
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constructor(gen) {
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/** @private {function():T} */
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this.gen_ = gen;
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/** @private {T|undefined} */
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this.value_ = undefined;
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}
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/**
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* @return {T}
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* @export
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*/
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value() {
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if (this.value_ == undefined) {
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// Compiler complains about unknown fields without this cast.
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this.value_ = /** @type {*} */ (this.gen_());
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goog.asserts.assert(
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this.value_ != undefined, 'Unable to create lazy value');
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}
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return this.value_;
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}
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};
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