/**

* 使用共享内存的PHP循环内存队列实现

* 支持多进程, 支持各种数据类型的存储

* 注: 完成入队或出队操作,尽快使用unset(), 以释放临界区

* /

class SHMQueue

{

private $maxQSize = 0; // 队列最大长度

private $front = 0; // 队头指针

private $rear = 0; // 队尾指针

private $blockSize = 256; // 块的大小(byte)

private $memSize = 25600; // 最大共享内存(byte)

private $shmId = 0;

private $filePtr = './shmq.ptr';

private $semId = 0;

public function __construct()

{

$shmkey = ftok(__FILE__, 't');

$this->shmId = shmop_open($shmkey, "c", 0644, $this->memSize );

$this->maxQSize = $this->memSize / $this->blockSize;

// 申請一个信号量

$this->semId = sem_get($shmkey, 1);

sem_acquire($this->semId); // 申请进入临界区

$this->init();

}

private function init()

{

if ( file_exists($this->filePtr) ){

$contents = file_get_contents($this->filePtr);

$data = explode( '|', $contents );

if ( isset($data[0]) && isset($data[1])){

$this->front = (int)$data[0];

$this->rear = (int)$data[1];

}

}

}

public function getLength()

{

return (($this->rear - $this->front + $this->memSize) % ($this->memSize) )/$this->blockSize;

}

public function enQueue( $value )

{

if ( $this->ptrInc($this->rear) == $this->front ){ // 队满

return false;

}

$data = $this->encode($value);

shmop_write($this->shmId, $data, $this->rear );

$this->rear = $this->ptrInc($this->rear);

return true;

}

public function deQueue()

{

if ( $this->front == $this->rear ){ // 队空

return false;

}

$value = shmop_read($this->shmId, $this->front, $this->blockSize-1);

$this->front = $this->ptrInc($this->front);

return $this->decode($value);

}

private function ptrInc( $ptr )

{

return ($ptr + $this->blockSize) % ($this->memSize);

}

private function encode( $value )

{

$data = serialize($value) . "__eof";

if ( strlen($data) > $this->blockSize -1 ){

throw new Exception(strlen($data)." is overload block size!");

}

return $data;

}

private function decode( $value )

{

$data = explode("__eof", $value);

return unserialize($data[0]);

}

public function __destruct()

{

$data = $this->front . '|' . $this->rear;

file_put_contents($this->filePtr, $data);

sem_release($this->semId); // 出临界区, 释放信号量

}

}

//*******************************************

使用的样例代码如下:

// 进队操作

$shmq = new SHMQueue();

$data = 'test data';

$shmq->enQueue($data);

unset($shmq);

// 出队操作

$shmq = new SHMQueue();

$data = $shmq->deQueue();

unset($shmq);

?>