PHP implements a two-way queue

What is PHP bidirectional queue? Using PHP to write a two-way queue is actually examining several built-in array functions in PHP. Let's take a look at the specific code below.

用PHP写一个双向队列<?php 
    class Deque{        public $queue = array();        /**
         * 尾部入对
         * @param [type] $value [description]         */
        public function addLast($value){            return array_push($this->queue,$value);
        }        /**
         * 尾部出队
         * @return [type] [description]         */
        public function removeLast(){            return array_pop($this->queue);
        }        /**
         * 头部入队
         * @param [type] $value [description]         */
        public function addFirst($value){            return array_unshift($this->queue, $value);
        }        /**
         * 头部出队
         * @return [type] [description]         */
        public function removeFirst(){            return array_shift($this->queue);
        }        /**
         * 清空队列
         * @return [type] [description]         */
        public function makeEmpty(){            unset($this->queue);
        }        /**
         * 获取列头
         * @return [type] [description]         */
        public function getFirst(){            return reset($this->queue);
        }        /**
         * 获取列尾
         * @return [type] [description]         */
        public function getLast(){            return end($this->queue);
        }        /**
         * 获取长度
         * @return [type] [description]         */
        public function getLength(){            return count($this->queue);
        }
    } ?>加上一些限制条件后：<?php 
/** php 双向队列。支持限定队列长度，输入受限，输出受限，及输出必须与输入同端几种设置 
*  Func: 
*  public frontAdd   前端入列 
*  public frontRemove 前端出列 
*  public rearAdd   后端入列 
*  pulbic rearRemove  后端出列 
*  public clear    清空对列 
*  public isFull    判断对列是否已满 
*  private getLength  获取对列长度 
*  private setAddNum  记录入列,输出依赖输入时调用 
*  private setRemoveNum 记录出列,输出依赖输入时调用 
*  private checkRemove 检查是否输出依赖输入 
*/ class DEQue{ // class start 
  private $_queue = array(); // 对列 
  private $_maxLength = 0;  // 对列最大长度，0表示不限 
  private $_type = 0;    // 对列类型 
  private $_frontNum = 0;  // 前端插入的数量 
  private $_rearNum = 0;   // 后端插入的数量 
  /** 初始化 
  * @param $type    对列类型 
  *          1:两端均可输入输出 
  *          2:前端只能输入，后端可输入输出 
  *          3:前端只能输出，后端可输入输出 
  *          4:后端只能输入，前端可输入输出 
  *          5:后端只能输出，前端可输入输出 
  *          6:两端均可输入输出，在哪端输入只能从哪端输出 
  * @param $maxlength 对列最大长度 
  */
  public function __construct($type=1, $maxlength=0){ 
    $this->_type = in_array($type, array(1,2,3,4,5,6))? $type : 1; 
    $this->_maxLength = intval($maxlength); 
  } 
  // 前端入列 
  // @param Mixed  $data 数据 
  //@return boolean 
  public function frontAdd($data=null){ 
    if($this->_type==3){ // 前端输入限制 
      return false; 
    } 
    if(isset($data) && !$this->isFull()){ 
      array_unshift($this->_queue, $data); 
      $this->setAddNum(1); 
      return true; 
    } 
    return false; 
  } 
  //前端出列 
  //@return Array
  public function frontRemove(){ 
    if($this->_type==2){ // 前端输出限制 
      return null; 
    } 
    if(!$this->checkRemove(1)){ // 检查是否依赖输入 
      return null; 
    } 
    $data = null; 
    if($this->getLength()>0){ 
      $data = array_shift($this->_queue); 
      $this->setRemoveNum(1); 
    } 
    return $data; 
  } 
  // 后端入列 
  // @param Mixed  $data 数据 
  //@return boolean 
  public function rearAdd($data=null){ 
    if($this->_type==5){ // 后端输入限制 
      return false; 
    } 
    if(isset($data) && !$this->isFull()){ 
      array_push($this->_queue, $data); 
      $this->setAddNum(2); 
      return true; 
    } 
    return false; 
  } 
  // 后端出列 
  // @return Array 
  public function rearRemove(){ 
    if($this->_type==4){ // 后端输出限制 
      return null; 
    } 
    if(!$this->checkRemove(2)){ // 检查是否依赖输入 
      return null; 
    } 
    $data = null; 
    if($this->getLength()>0){ 
      $data = array_pop($this->_queue); 
      $this->setRemoveNum(2); 
    } 
    return $data; 
  } 
  //清空对列 
  //@return boolean 
  public function clear(){ 
    $this->_queue = array(); 
    $this->_frontNum = 0; 
    $this->_rearNum = 0; 
    return true; 
  }  //判断对列是否已满 
  //@return boolean 
  public function isFull(){ 
    $bIsFull = false; 
    if($this->_maxLength!=0 && $this->_maxLength==$this->getLength()){ 
      $bIsFull = true; 
    } 
    return $bIsFull; 
  } 
  //获取当前对列长度 
  //@return int 
  private function getLength(){ 
    return count($this->_queue); 
  } 
  //记录入列,输出依赖输入时调用 
  // @param int $endpoint 端点 1:front 2:rear 
  private function setAddNum($endpoint){ 
    if($this->_type==6){ 
      if($endpoint==1){ 
        $this->_frontNum ++; 
      }else{ 
        $this->_rearNum ++; 
      } 
    } 
  } 
  //记录出列,输出依赖输入时调用 
  //@param int $endpoint 端点 1:front 2:rear 
  private function setRemoveNum($endpoint){ 
    if($this->_type==6){ 
      if($endpoint==1){ 
        $this->_frontNum --; 
      }else{ 
        $this->_rearNum --; 
      } 
    } 
  }  //检查是否输出依赖输入 
  //@param int $endpoint 端点 1:front 2:rear 
  private function checkRemove($endpoint){ 
    if($this->_type==6){ 
      if($endpoint==1){ 
        return $this->_frontNum>0; 
      }else{ 
        return $this->_rearNum>0; 
      } 
    } 
    return true; 
  } 
} // class end ?>

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