半天撸完一个PHP 实现LRU 算法的知识

/** * 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key public 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; } }

/** * 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()."
"; $node=$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(); } } }

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(); }