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// Copyright 2006 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 Datastructure: Queue.
*
*
* This file provides the implementation of a FIFO Queue structure.
* API is similar to that of com.google.common.collect.IntQueue
*/
goog.provide('goog.structs.Queue');
goog.require('goog.array');
/**
* Class for FIFO Queue data structure.
*
* @constructor
*/
goog.structs.Queue = function() {
this.elements_ = [];
};
/**
* The index of the next element to be removed from the queue.
* @private
* @type {number}
*/
goog.structs.Queue.prototype.head_ = 0;
/**
* The index at which the next element would be added to the queue.
* @private
* @type {number}
*/
goog.structs.Queue.prototype.tail_ = 0;
/**
* Puts the specified element on this queue.
* @param {*} element The element to be added to the queue.
*/
goog.structs.Queue.prototype.enqueue = function(element) {
this.elements_[this.tail_++] = element;
};
/**
* Retrieves and removes the head of this queue.
* @return {*} The element at the head of this queue. Returns undefined if the
* queue is empty.
*/
goog.structs.Queue.prototype.dequeue = function() {
if (this.head_ == this.tail_) {
return undefined;
}
var result = this.elements_[this.head_];
delete this.elements_[this.head_];
this.head_++;
return result;
};
/**
* Retrieves but does not remove the head of this queue.
* @return {*} The element at the head of this queue. Returns undefined if the
* queue is empty.
*/
goog.structs.Queue.prototype.peek = function() {
if (this.head_ == this.tail_) {
return undefined;
}
return this.elements_[this.head_];
};
/**
* Returns the number of elements in this queue.
* @return {number} The number of elements in this queue.
*/
goog.structs.Queue.prototype.getCount = function() {
return this.tail_ - this.head_;
};
/**
* Returns true if this queue contains no elements.
* @return {boolean} true if this queue contains no elements.
*/
goog.structs.Queue.prototype.isEmpty = function() {
return this.tail_ - this.head_ == 0;
};
/**
* Removes all elements from the queue.
*/
goog.structs.Queue.prototype.clear = function() {
this.elements_.length = 0;
this.head_ = 0;
this.tail_ = 0;
};
/**
* Returns true if the given value is in the queue.
* @param {*} obj The value to look for.
* @return {boolean} Whether the object is in the queue.
*/
goog.structs.Queue.prototype.contains = function(obj) {
return goog.array.contains(this.elements_, obj);
};
/**
* Removes the first occurrence of a particular value from the queue.
* @param {*} obj Object to remove.
* @return {boolean} True if an element was removed.
*/
goog.structs.Queue.prototype.remove = function(obj) {
var index = goog.array.indexOf(this.elements_, obj);
if (index < 0) {
return false;
}
if (index == this.head_) {
this.dequeue();
} else {
goog.array.removeAt(this.elements_, index);
this.tail_--;
}
return true;
};
/**
* Returns all the values in the queue.
* @return {Array} An array of the values in the queue.
*/
goog.structs.Queue.prototype.getValues = function() {
return this.elements_.slice(this.head_, this.tail_);
};
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