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// Copyright 2015 The Closure Library Authors. All Rights Reserved.
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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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 * @fileoverview Simple freelist.
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 *
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 * An anterative to goog.structs.SimplePool, it imposes the requirement that the
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 * objects in the list contain a "next" property that can be used to maintain
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 * the pool.
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 */
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goog.provide('goog.async.FreeList');
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/**
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 * @template ITEM
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 */
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goog.async.FreeList = goog.defineClass(null, {
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  /**
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   * @param {function():ITEM} create
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   * @param {function(ITEM):void} reset
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   * @param {number} limit
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   */
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  constructor: function(create, reset, limit) {
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    /** @private @const {number} */
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    this.limit_ = limit;
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    /** @private @const {function()} */
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    this.create_ = create;
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    /** @private @const {function(ITEM):void} */
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    this.reset_ = reset;
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    /** @private {number} */
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    this.occupants_ = 0;
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    /** @private {ITEM} */
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    this.head_ = null;
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  },
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  /**
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   * @return {ITEM}
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   */
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  get: function() {
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    var item;
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    if (this.occupants_ > 0) {
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      this.occupants_--;
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      item = this.head_;
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      this.head_ = item.next;
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      item.next = null;
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    } else {
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      item = this.create_();
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    }
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    return item;
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  },
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  /**
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   * @param {ITEM} item An item available for possible future reuse.
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   */
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  put: function(item) {
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    this.reset_(item);
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    if (this.occupants_ < this.limit_) {
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      this.occupants_++;
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      item.next = this.head_;
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      this.head_ = item;
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    }
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  },
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  /**
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   * Visible for testing.
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   * @package
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   * @return {number}
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   */
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  occupants: function() { return this.occupants_; }
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});
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