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1 // Copyright 2014 The Chromium Authors. All rights reserved. | 1 // Copyright 2014 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 /** | 5 /** |
6 * @fileoverview Provides a system for memoizing computations applied to | 6 * @fileoverview Provides a system for memoizing computations applied to |
7 * DOM nodes within the same call stack. | 7 * DOM nodes within the same call stack. |
8 * | 8 * |
9 * To make a function memoizable - suppose you have a function | 9 * To make a function memoizable - suppose you have a function |
10 * isAccessible that takes a node and returns a boolean: | 10 * isAccessible that takes a node and returns a boolean: |
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44 * @constructor | 44 * @constructor |
45 */ | 45 */ |
46 cvox.Memoize = function() { | 46 cvox.Memoize = function() { |
47 }; | 47 }; |
48 | 48 |
49 /** | 49 /** |
50 * The cache: a map from string function name to a WeakMap from DOM node | 50 * The cache: a map from string function name to a WeakMap from DOM node |
51 * to function result. This variable is null when we're out of scope, and it's | 51 * to function result. This variable is null when we're out of scope, and it's |
52 * a map from string to WeakMap to result when we're in scope. | 52 * a map from string to WeakMap to result when we're in scope. |
53 * | 53 * |
54 * @type {?Object.<string, WeakMap.<Node, *> >} | 54 * @type {?Object<string, WeakMap<Node, *> >} |
55 * @private | 55 * @private |
56 */ | 56 */ |
57 cvox.Memoize.nodeMap_ = null; | 57 cvox.Memoize.nodeMap_ = null; |
58 | 58 |
59 /** | 59 /** |
60 * Keeps track of how many nested times scope() has been called. | 60 * Keeps track of how many nested times scope() has been called. |
61 * @type {number} | 61 * @type {number} |
62 * @private | 62 * @private |
63 */ | 63 */ |
64 cvox.Memoize.scopeCount_ = 0; | 64 cvox.Memoize.scopeCount_ = 0; |
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124 if (result === undefined) { | 124 if (result === undefined) { |
125 result = functionClosure(node); | 125 result = functionClosure(node); |
126 if (result === undefined) { | 126 if (result === undefined) { |
127 throw 'A memoized function cannot return undefined.'; | 127 throw 'A memoized function cannot return undefined.'; |
128 } | 128 } |
129 cvox.Memoize.nodeMap_[functionName].set(node, result); | 129 cvox.Memoize.nodeMap_[functionName].set(node, result); |
130 } | 130 } |
131 | 131 |
132 return result; | 132 return result; |
133 }; | 133 }; |
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