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// Copyright 2015 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.
goog.provide('goog.async.WorkItem');
goog.provide('goog.async.WorkQueue');
goog.require('goog.asserts');
goog.require('goog.async.FreeList');
// TODO(johnlenz): generalize the WorkQueue if this is used by more
// than goog.async.run.
/**
* A low GC workqueue. The key elements of this design:
* - avoids the need for goog.bind or equivalent by carrying scope
* - avoids the need for array reallocation by using a linked list
* - minimizes work entry objects allocation by recycling objects
* @constructor
* @final
* @struct
*/
goog.async.WorkQueue = function() {
this.workHead_ = null;
this.workTail_ = null;
};
/** @define {number} The maximum number of entries to keep for recycling. */
goog.define('goog.async.WorkQueue.DEFAULT_MAX_UNUSED', 100);
/** @const @private {goog.async.FreeList<goog.async.WorkItem>} */
goog.async.WorkQueue.freelist_ = new goog.async.FreeList(
function() { return new goog.async.WorkItem(); },
function(item) { item.reset(); }, goog.async.WorkQueue.DEFAULT_MAX_UNUSED);
/**
* @param {function()} fn
* @param {Object|null|undefined} scope
*/
goog.async.WorkQueue.prototype.add = function(fn, scope) {
var item = this.getUnusedItem_();
item.set(fn, scope);
if (this.workTail_) {
this.workTail_.next = item;
this.workTail_ = item;
} else {
goog.asserts.assert(!this.workHead_);
this.workHead_ = item;
this.workTail_ = item;
}
};
/**
* @return {goog.async.WorkItem}
*/
goog.async.WorkQueue.prototype.remove = function() {
var item = null;
if (this.workHead_) {
item = this.workHead_;
this.workHead_ = this.workHead_.next;
if (!this.workHead_) {
this.workTail_ = null;
}
item.next = null;
}
return item;
};
/**
* @param {goog.async.WorkItem} item
*/
goog.async.WorkQueue.prototype.returnUnused = function(item) {
goog.async.WorkQueue.freelist_.put(item);
};
/**
* @return {goog.async.WorkItem}
* @private
*/
goog.async.WorkQueue.prototype.getUnusedItem_ = function() {
return goog.async.WorkQueue.freelist_.get();
};
/**
* @constructor
* @final
* @struct
*/
goog.async.WorkItem = function() {
/** @type {?function()} */
this.fn = null;
/** @type {Object|null|undefined} */
this.scope = null;
/** @type {?goog.async.WorkItem} */
this.next = null;
};
/**
* @param {function()} fn
* @param {Object|null|undefined} scope
*/
goog.async.WorkItem.prototype.set = function(fn, scope) {
this.fn = fn;
this.scope = scope;
this.next = null;
};
/** Reset the work item so they don't prevent GC before reuse */
goog.async.WorkItem.prototype.reset = function() {
this.fn = null;
this.scope = null;
this.next = null;
};
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