<?php
 /**
 * 一致性哈希memcache分布式，采用的是虚拟节点的方式解决分布均匀性问题,查找节点采用二分法快速查找
 * the last known user to change this file in the repository  <$LastChangedBy: nash.xiong [        DISCUZ_CODE_0        ]gt;
 * @author nash.xiong <nash.xiong@gmail.com>
 * @copyright Copyright &copy; 2003-2012 phpd.cn
 * @license 
 */
 class memcacheHashMap {

         private $_node = array();
         private $_nodeData = http://www.mamicode.com/array();"%u", crc32($value . ‘_‘ . $i))] = $value . ‘_‘ . $i;
                         }
                 }
                 ksort($this->_node);
         }

         private function __clone(){}
         
         /**
          * 单例，保证只有一个实例
          */
         static public function getInstance() {
                 static $memcacheObj = null;
                 if (!is_object($memcacheObj)) {
                         $memcacheObj = new self();
                 }
                 return $memcacheObj;
         }
         
         /**
          * 根据key做一致性hash后连接到一台物理memcache服务器
          * @param string $key
          */
         private function _connectMemcache($key) {
                 $this->_nodeData = http://www.mamicode.com/array_keys($this->_node);"%u", crc32($key));
                 $nodeKey = $this->_findServerNode();
                 //如果超出环，从头再用二分法查找一个最近的，然后环的头尾做判断，取最接近的节点
                 if ($this->_keyNode > end($this->_nodeData)) {
                         $this->_keyNode -= end($this->_nodeData);
                         $nodeKey2 = $this->_findServerNode();
                         if (abs($nodeKey2 - $this->_keyNode) < abs($nodeKey - $this->_keyNode))  $nodeKey = $nodeKey2;
                 }
                 var_dump($this->_node[$nodeKey]);
                 list($config, $num) = explode(‘_‘, $this->_node[$nodeKey]);
                 if (!$config) throw new Exception(‘Cache config Error‘);
                 if (!isset($this->_memcache[$config])) {
                         $this->_memcache[$config] = new Memcache;
                         list($host, $port) = explode(‘:‘, $config);
                         $this->_memcache[$config]->connect($host, $port);
                 }
                 return $this->_memcache[$config];
         }
         
         /**
          * 采用二分法从虚拟memcache节点中查找最近的节点
          * @param unknown_type $m
          * @param unknown_type $b
          */
         private function _findServerNode($m = 0, $b = 0) {
             $total = count($this->_nodeData);
             if ($total != 0 && $b == 0) $b = $total - 1;
             if ($m < $b){
                 $avg = intval(($m+$b) / 2);
                 if ($this->_nodeData[$avg] == $this->_keyNode) return $this->_nodeData[$avg];
                 elseif ($this->_keyNode < $this->_nodeData[$avg] && ($avg-1 >= 0)) return $this->_findServerNode($m, $avg-1);
                 else return $this->_findServerNode($avg+1, $b);
             }
                 if (abs($this->_nodeData[$b] - $this->_keyNode) < abs($this->_nodeData[$m] - $this->_keyNode))  return $this->_nodeData[$b];
                 else return $this->_nodeData[$m];
         }
         
         public function set($key, $value, $expire = 0) {
                 return $this->_connectMemcache($key)->set($key, json_encode($value), 0, $expire);
         }
         
         public function add($key, $value, $expire = 0) {
                 return $this->_connectMemcache($key)->add($key, json_encode($value), 0, $expire);
         }
         
         public function get($key) {
                 return json_decode($this->_connectMemcache($key)->get($key), true);
         }
         
         public function delete($key) {
                 return $this->_connectMemcache($key)->delete($key);
         }
         
 }

 $runData[‘BEGIN_TIME‘] = microtime(true);
 //测试一万次set加get
 for($i=0;$i<10000;$i++) {
         $key = md5(mt_rand());
         $b = memcacheHashMap::getInstance()->set($key, time(), 10);
 }

 var_dump(number_format(microtime(true) - $runData[‘BEGIN_TIME‘],6));
 $runData[‘BEGIN_TIME‘] = microtime(true); $m= new Memcache;
 $m->connect(‘127.0.0.1‘, 11211); 
 for($i=0;$i<10000;$i++) {
         $key = md5(mt_rand());
         $b = $m->set($key, time(), 0, 10);
 }
 var_dump(number_format(microtime(true) - $runData[‘BEGIN_TIME‘],6));