| // Copyright 2008 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 Tool for caching the result of expensive deterministic |
| * functions. |
| * |
| * @see http://en.wikipedia.org/wiki/Memoization |
| * |
| */ |
| |
| goog.provide('goog.memoize'); |
| |
| |
| /** |
| * Decorator around functions that caches the inner function's return values. |
| * |
| * To cache parameterless functions, see goog.functions.cacheReturnValue. |
| * |
| * @param {Function} f The function to wrap. Its return value may only depend |
| * on its arguments and 'this' context. There may be further restrictions |
| * on the arguments depending on the capabilities of the serializer used. |
| * @param {function(number, Object): string=} opt_serializer A function to |
| * serialize f's arguments. It must have the same signature as |
| * goog.memoize.simpleSerializer. It defaults to that function. |
| * @this {Object} The object whose function is being wrapped. |
| * @return {!Function} The wrapped function. |
| */ |
| goog.memoize = function(f, opt_serializer) { |
| var serializer = opt_serializer || goog.memoize.simpleSerializer; |
| |
| return function() { |
| if (goog.memoize.ENABLE_MEMOIZE) { |
| // In the strict mode, when this function is called as a global function, |
| // the value of 'this' is undefined instead of a global object. See: |
| // https://developer.mozilla.org/en/JavaScript/Strict_mode |
| var thisOrGlobal = this || goog.global; |
| // Maps the serialized list of args to the corresponding return value. |
| var cache = thisOrGlobal[goog.memoize.CACHE_PROPERTY_] || |
| (thisOrGlobal[goog.memoize.CACHE_PROPERTY_] = {}); |
| var key = serializer(goog.getUid(f), arguments); |
| return cache.hasOwnProperty(key) ? cache[key] : |
| (cache[key] = f.apply(this, arguments)); |
| } else { |
| return f.apply(this, arguments); |
| } |
| }; |
| }; |
| |
| |
| /** |
| * @define {boolean} Flag to disable memoization in unit tests. |
| */ |
| goog.define('goog.memoize.ENABLE_MEMOIZE', true); |
| |
| |
| /** |
| * Clears the memoization cache on the given object. |
| * @param {Object} cacheOwner The owner of the cache. This is the {@code this} |
| * context of the memoized function. |
| */ |
| goog.memoize.clearCache = function(cacheOwner) { |
| cacheOwner[goog.memoize.CACHE_PROPERTY_] = {}; |
| }; |
| |
| |
| /** |
| * Name of the property used by goog.memoize as cache. |
| * @type {string} |
| * @private |
| */ |
| goog.memoize.CACHE_PROPERTY_ = 'closure_memoize_cache_'; |
| |
| |
| /** |
| * Simple and fast argument serializer function for goog.memoize. |
| * Supports string, number, boolean, null and undefined arguments. Doesn't |
| * support \x0B characters in the strings. |
| * @param {number} functionUid Unique identifier of the function whose result |
| * is cached. |
| * @param {Object} args The arguments that the function to memoize is called |
| * with. Note: it is an array-like object, because supports indexing and |
| * has the length property. |
| * @return {string} The list of arguments with type information concatenated |
| * with the functionUid argument, serialized as \x0B-separated string. |
| */ |
| goog.memoize.simpleSerializer = function(functionUid, args) { |
| var context = [functionUid]; |
| for (var i = args.length - 1; i >= 0; --i) { |
| context.push(typeof args[i], args[i]); |
| } |
| return context.join('\x0B'); |
| }; |