/** * Copyright (c) 2013-present, Facebook, Inc. * * This source code is licensed under the MIT license found in the * LICENSE file in the root directory of this source tree. * * @providesModule PooledClass * @flow */ 'use strict'; const invariant = require('fbjs/lib/invariant'); /** * Static poolers. Several custom versions for each potential number of * arguments. A completely generic pooler is easy to implement, but would * require accessing the `arguments` object. In each of these, `this` refers to * the Class itself, not an instance. If any others are needed, simply add them * here, or in their own files. */ const oneArgumentPooler = function(copyFieldsFrom) { const Klass = this; if (Klass.instancePool.length) { const instance = Klass.instancePool.pop(); Klass.call(instance, copyFieldsFrom); return instance; } else { return new Klass(copyFieldsFrom); } }; const twoArgumentPooler = function(a1, a2) { const Klass = this; if (Klass.instancePool.length) { const instance = Klass.instancePool.pop(); Klass.call(instance, a1, a2); return instance; } else { return new Klass(a1, a2); } }; const threeArgumentPooler = function(a1, a2, a3) { const Klass = this; if (Klass.instancePool.length) { const instance = Klass.instancePool.pop(); Klass.call(instance, a1, a2, a3); return instance; } else { return new Klass(a1, a2, a3); } }; const fourArgumentPooler = function(a1, a2, a3, a4) { const Klass = this; if (Klass.instancePool.length) { const instance = Klass.instancePool.pop(); Klass.call(instance, a1, a2, a3, a4); return instance; } else { return new Klass(a1, a2, a3, a4); } }; const standardReleaser = function(instance) { const Klass = this; invariant( instance instanceof Klass, 'Trying to release an instance into a pool of a different type.', ); instance.destructor(); if (Klass.instancePool.length < Klass.poolSize) { Klass.instancePool.push(instance); } }; const DEFAULT_POOL_SIZE = 10; const DEFAULT_POOLER = oneArgumentPooler; type Pooler = any; /** * Augments `CopyConstructor` to be a poolable class, augmenting only the class * itself (statically) not adding any prototypical fields. Any CopyConstructor * you give this may have a `poolSize` property, and will look for a * prototypical `destructor` on instances. * * @param {Function} CopyConstructor Constructor that can be used to reset. * @param {Function} pooler Customizable pooler. */ const addPoolingTo = function( CopyConstructor: Class, pooler: Pooler, ): Class & { getPooled( ...args: $ReadOnlyArray ): /* arguments of the constructor */ T, release(instance: mixed): void, } { // Casting as any so that flow ignores the actual implementation and trusts // it to match the type we declared const NewKlass = (CopyConstructor: any); NewKlass.instancePool = []; NewKlass.getPooled = pooler || DEFAULT_POOLER; if (!NewKlass.poolSize) { NewKlass.poolSize = DEFAULT_POOL_SIZE; } NewKlass.release = standardReleaser; return NewKlass; }; const PooledClass = { addPoolingTo: addPoolingTo, oneArgumentPooler: (oneArgumentPooler: Pooler), twoArgumentPooler: (twoArgumentPooler: Pooler), threeArgumentPooler: (threeArgumentPooler: Pooler), fourArgumentPooler: (fourArgumentPooler: Pooler), }; module.exports = PooledClass;