本文讲解PHP如何实现的memcache环形队列类实例
这里介绍了PHP实现的memcache环形队列类。没咋学过数据结构，因为业务需要，所以只是硬着头皮模拟的！ 参考PHP memcache 队列代码。为使队列随时可入可出，且不受int长度越界危险（单链采取Head自增的话不作处理有越界可能），所以索性改写成环形队列。可能还有BUG，忘见谅！
<?php /** * PHP memcache 环形队列类 * 原作者 LKK/lianq.net * 修改 FoxHunter * 因业务需要只保留的队列中的Pop和Push,修改过期时间为0即永久 */ class MQueue { public static $client; private $expire; //过期时间,秒,1~2592000,即30天内 private $sleepTime; //等待解锁时间,微秒 private $queueName; //队列名称,唯一值 private $retryNum; //尝试次数 private $MAXNUM; //最大队列容量 private $canRewrite; //是否可以覆写开关，满出来的内容从头部开始覆盖重写原来的数据 private $HEAD; //下一步要进入的指针位置 private $TAIL; //下一步要进入的指针位置 private $LEN; //队列现有长度 const LOCK_KEY = '_Fox_MQ_LOCK_'; //锁存储标示 const LENGTH_KEY = '_Fox_MQ_LENGTH_'; //队列现长度存储标示 const VALU_KEY = '_Fox_MQ_VAL_'; //队列键值存储标示 const HEAD_KEY = '_Fox_MQ_HEAD_'; //队列HEAD指针位置标示 const TAIL_KEY = '_Fox_MQ_TAIL_'; //队列TAIL指针位置标示 /* * 构造函数 * 对于同一个$queueName，实例化时必须保障构造函数的参数值一致，否则pop和push会导队列顺序混乱 */ public function __construct($queueName = '', $maxqueue = 1, $canRewrite = false, $expire = 0, $config = '') { if (empty($config)) { self::$client = memcache_pconnect('127.0.0.1', 11211); } elseif (is_array($config)) { //array('host'=>'127.0.0.1','port'=>'11211') self::$client = memcache_pconnect($config['host'], $config['port']); } elseif (is_string($config)) { //"127.0.0.1:11211" $tmp = explode(':', $config); $conf['host'] = isset($tmp[0]) ? $tmp[0] : '127.0.0.1'; $conf['port'] = isset($tmp[1]) ? $tmp[1] : '11211'; self::$client = memcache_pconnect($conf['host'], $conf['port']); } if (!self::$client) return false; ignore_user_abort(true); //当客户断开连接,允许继续执行 set_time_limit(0); //取消脚本执行延时上限 $this->access = false; $this->sleepTime = 1000; $expire = (empty($expire)) ? 0 : (int) $expire + 1; $this->expire = $expire; $this->queueName = $queueName; $this->retryNum = 20000; $this->MAXNUM = $maxqueue != null ? $maxqueue : 1; $this->canRewrite = $canRewrite; $this->getHeadAndTail(); if (!isset($this->HEAD) || empty($this->HEAD)) $this->HEAD = 0; if (!isset($this->TAIL) || empty($this->TAIL)) $this->TAIL = 0; if (!isset($this->LEN) || empty($this->LEN)) $this->LEN = 0; } //获取队列首尾指针信息和长度 private function getHeadAndTail() { $this->HEAD = (int) memcache_get(self::$client, $this->queueName . self::HEAD_KEY); $this->TAIL = (int) memcache_get(self::$client, $this->queueName . self::TAIL_KEY); $this->LEN = (int) memcache_get(self::$client, $this->queueName . self::LENGTH_KEY); } // 利用memcache_add原子性加锁 private function lock() { if ($this->access === false) { $i = 0; while (!memcache_add(self::$client, $this->queueName . self::LOCK_KEY, 1, false, $this->expire)) { usleep($this->sleepTime); @$i++; if ($i > $this->retryNum) { //尝试等待N次 return false; break; } } return $this->access = true; } return false; } //更新头部指针指向,指向下一个位置 private function incrHead() { //$this->getHeadAndTail(); //获取最新指针信息 ,由于本方法体均在锁内调用，其锁内已调用了此方法，本行注释 $this->HEAD++; //头部指针下移 if ($this->HEAD >= $this->MAXNUM) { $this->HEAD = 0; //边界值修正 } ; $this->LEN--; //Head的移动由Pop触发，所以相当于数量减少 if ($this->LEN < 0) { $this->LEN = 0; //边界值修正 } ; memcache_set(self::$client, $this->queueName . self::HEAD_KEY, $this->HEAD, false, $this->expire); //更新 memcache_set(self::$client, $this->queueName . self::LENGTH_KEY, $this->LEN, false, $this->expire); //更新 } //更新尾部指针指向，指向下一个位置 private function incrTail() { //$this->getHeadAndTail(); //获取最新指针信息，由于本方法体均在锁内调用，其锁内已调用了此方法，本行注释 $this->TAIL++; //尾部指针下移 if ($this->TAIL >= $this->MAXNUM) { $this->TAIL = 0; //边界值修正 } ; $this->LEN++; //Head的移动由Push触发，所以相当于数量增加 if ($this->LEN >= $this->MAXNUM) { $this->LEN = $this->MAXNUM; //边界值长度修正 } ; memcache_set(self::$client, $this->queueName . self::TAIL_KEY, $this->TAIL, false, $this->expire); //更新 memcache_set(self::$client, $this->queueName . self::LENGTH_KEY, $this->LEN, false, $this->expire); //更新 } // 解锁 private function unLock() { memcache_delete(self::$client, $this->queueName . self::LOCK_KEY); $this->access = false; } //判断是否满队列 public function isFull() { //外部直接调用的时候由于没有锁所以此处的值是个大概值，并不很准确，但是内部调用由于在前面有lock，所以可信 if ($this->canRewrite) return false; return $this->LEN == $this->MAXNUM ? true : false; } //判断是否为空 public function isEmpty() { //外部直接调用的时候由于没有锁所以此处的值是个大概值，并不很准确，但是内部调用由于在前面有lock，所以可信 return $this->LEN == 0 ? true : false; } public function getLen() { //外部直接调用的时候由于没有锁所以此处的值是个大概值，并不很准确，但是内部调用由于在前面有lock，所以可信 return $this->LEN; } /* * push值 * @param mixed 值 * @return bool */ public function push($data = '') { $result = false; if (empty($data)) return $result; if (!$this->lock()) { return $result; } $this->getHeadAndTail(); //获取最新指针信息 if ($this->isFull()) { //只有在非覆写下才有Full概念 $this->unLock(); return false; } if (memcache_set(self::$client, $this->queueName . self::VALU_KEY . $this->TAIL, $data, MEMCACHE_COMPRESSED, $this->expire)) { //当推送后，发现尾部和头部重合（此时指针还未移动），且右边仍有未由Head读取的数据，那么移动Head指针，避免尾部指针跨越Head if ($this->TAIL == $this->HEAD && $this->LEN >= 1) { $this->incrHead(); } $this->incrTail(); //移动尾部指针 $result = true; } $this->unLock(); return $result; } /* * Pop一个值 * @param [length] int 队列长度 * @return array */ public function pop($length = 0) { if (!is_numeric($length)) return false; if (!$this->lock()) return false; $this->getHeadAndTail(); if (empty($length)) $length = $this->LEN; //默认读取所有 if ($this->isEmpty()) { $this->unLock(); return false; } //获取长度超出队列长度后进行修正 if ($length > $this->LEN) $length = $this->LEN; $data = $this->popKeyArray($length); $this->unLock(); return $data; } /* * pop某段长度的值 * @param [length] int 队列长度 * @return array */ private function popKeyArray($length) { $result = array(); if (empty($length)) return $result; for ($k = 0; $k < $length; $k++) { $result[] = @memcache_get(self::$client, $this->queueName . self::VALU_KEY . $this->HEAD); @memcache_delete(self::$client, $this->queueName . self::VALU_KEY . $this->HEAD, 0); //当提取值后，发现头部和尾部重合（此时指针还未移动），且右边没有数据，即队列中最后一个 //数据被完全掏空，此时指针停留在本地不移动，队列长度变为0 if ($this->TAIL == $this->HEAD && $this->LEN <= 1) { $this->LEN = 0; memcache_set(self::$client, $this->queueName . self::LENGTH_KEY, $this->LEN, false, $this->expire); //更新 break; } else { $this->incrHead(); //首尾未重合，或者重合但是仍有未读取出的数据，均移动HEAD指针到下一处待读取位置 } } return $result; } /* * 重置队列 * * @return NULL */ private function reset($all = false) { if ($all) { memcache_delete(self::$client, $this->queueName . self::HEAD_KEY, 0); memcache_delete(self::$client, $this->queueName . self::TAIL_KEY, 0); memcache_delete(self::$client, $this->queueName . self::LENGTH_KEY, 0); } else { $this->HEAD = $this->TAIL = $this->LEN = 0; memcache_set(self::$client, $this->queueName . self::HEAD_KEY, 0, false, $this->expire); memcache_set(self::$client, $this->queueName . self::TAIL_KEY, 0, false, $this->expire); memcache_set(self::$client, $this->queueName . self::LENGTH_KEY, 0, false, $this->expire); } } /* * 清除所有memcache缓存数据 * @return NULL */ public function memFlush() { memcache_flush(self::$client); } public function clear($all = false) { if (!$this->lock()) return false; $this->getHeadAndTail(); $Head = $this->HEAD; $Length = $this->LEN; $curr = 0; for ($i = 0; $i < $Length; $i++) { $curr = $this->$Head + $i; if ($curr >= $this->MAXNUM) { $this->HEAD = $curr = 0; } @memcache_delete(self::$client, $this->queueName . self::VALU_KEY . $curr, 0); } $this->unLock(); $this->reset($all); return true; } }
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