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整体设计

1:用数组保存缓存对象(Node);
2:缓存对象(Node)之间通过nextKey,preKey组成一个双向链表;
3:保存链表头 跟尾;

处理流程如下图:

主要代码

1:Node 节点类

/*** 缓存值保存类，* Class Node* @package app\common\model*/
class Node{private $preKey=null;//链表前一个节点private $nextKey=null;//链表后一个节点private $value=null;//当前的值private $key=null;//当前keypublic function __construct(string  $key,$value){$this->value=$value;$this->key=$key;}public function setPreKey($preValue){$this->preKey=$preValue;}public function setNextKey($nextValue){$this->nextKey=$nextValue;}public function getPreKey(){return $this->preKey;}public function getNextKey(){return $this->nextKey;}public function getValue(){return $this->value;}public function setValue($value){$this->value=$value;}public function setKey(string  $key){$this->key=$key;}public function getKey(){return $this->key;}
}

2:缓存类

/*** 实现lru缓存* Class LruCache* @package app\common\model*/
class LruCache
{public $cacheTable =[];private $headNode=null;private $lastNode=null;private $cacheCount=0;private $cacheMax=100;/*** 测试输出使用*/public function dumpAllData(){if (!empty($this->headNode)){$node=$this->headNode;while (!empty($node)){echo 'key='.$node->getKey().'  nextKey='.(empty($node->getNextKey())?'null':$node->getNextKey()->getKey()).' preKey='.(empty($node->getPreKey())?'null':$node->getPreKey()->getKey()).' value='.$node->getValue()."</br>";$node=$node->getNextKey();}}}/*** @param int $count*/public function setCacheMax(int $count){$this->cacheMax=$count;}/*** @param string $key* @param $value* @return bool*/public function set(string $key,$value){//设置值为null，则认为删除缓存节点if ($value===null){$this->del($key);return true;}//判断是否存在表中,存在则更新连表if (!empty($this->cacheTable[$key])){$this->updateList($key);return true;}//先判断是否要删除$this->shiftNode();$this->addNode($key,$value);return true;}/*** @param string $key* @return bool*/public function del(string $key){if (!empty($this->cacheTable[$key])){$node=&$this->cacheTable[$key];//摘出节点$this->jumpNode($node);//置空删除$node->setPreKey(null);$node->setNextKey(null);unset($this->cacheTable[$key]);return true;}return false;}/*** @param string $key* @return null*/public function get(string $key){if (!empty($this->cacheTable[$key])){$this->updateList($key);return $this->cacheTable[$key]->getValue();}return null;}//直接添加节点private function addNode($key,$value){$addNode=new Node($key,$value);if (!empty($this->headNode)){$this->headNode->setPreKey($addNode);}$addNode->setNextKey($this->headNode);//第一次保存最后一个节点为头节点if ($this->lastNode==null){$this->lastNode=$addNode;}$this->headNode=$addNode;$this->cacheTable[$key]=$addNode;$this->cacheCount++;}//主动删超出的缓存private function shiftNode(){while ($this->cacheCount>=$this->cacheMax){if (!empty($this->lastNode)){if (!empty($this->lastNode->getPreKey())){$this->lastNode->getPreKey()->setNextKey(null);}$lastKey=$this->lastNode->getKey();unset($this->cacheTable[$lastKey]);}$this->cacheCount--;}}//更新节点链表private function updateList($key){//这里需要使用引用传值$node=&$this->cacheTable[$key];//当前结点为头结点 直接不用处理if ($this->headNode===$node){return true;}//摘出结点$this->jumpNode($node);//跟头结点交换$node->setNextKey($this->headNode);$this->headNode->setPreKey($node);$node->setPreKey(null);$this->headNode=$node;return true;}//将某个节点摘出来private function jumpNode(Node &$node){if (!empty($node->getPreKey())){$node->getPreKey()->setNextKey($node->getNextKey());}if (!empty($node->getNextKey())){$node->getNextKey()->setPreKey($node->getPreKey());}//如果是最后一个节点,则更新最后节点为它的前节点if ($node->getNextKey()==null){$this->lastNode=$node->getPreKey();}//如果是头结点if ($node->getPreKey()==null){$this->headNode=$node->getNextKey();}}}

3:测试代码

    public function tt(){$cath=model("LruCache");$cath->setCacheMax(3);$cath->set("aa","aaaaaaaaaaa");$cath->set("bb","bbbbbbbbbbbb");$cath->set("cc","ccccccccccccc");$cath->get("aa");//        $cath->dumpAllData();$cath->set("dd","ddddddddddddd");
//        $cath->del("cc");
//        var_dump($cath->cacheTable);$cath->dumpAllData();exit();}

说明

其实php的数组就是有序的,也可以直接用php数组实现,这里只是提供一个实现的思路