php 共享内存

$shm_key = ftok(__FILE__, ‘t‘);

/**
 开辟一块共享内存
 
int $key , string $flags , int $mode , int $size 
$flags: a:访问只读内存段
        c:创建一个新内存段，或者如果该内存段已存在，尝试打开它进行读写
        w:可读写的内存段
        n:创建一个新内存段，如果该内存段已存在，则会失败
$mode: 八进制格式  0655
$size: 开辟的数据大小 字节

 */

$shm_id = shmop_open($shm_key, "c", 0644, 1024);

/**
 * 写入数据 数据必须是字符串格式 , 最后一个指偏移量
 * 注意：偏移量必须在指定的范围之内，否则写入不了
 * 
 */
$size = shmop_write($shm_id, ‘songjiankang‘, 0);
echo "write into {$size}";

#读取的范围也必须在申请的内存范围之内,否则失败
$data = shmop_read($shm_id, 0, 100);
var_dump($data);

#删除 只是做一个删除标志位，同时不在允许新的进程进程读取，当在没有任何进程读取时系统会自动删除
shmop_delete($shm_id);

#关闭该内存段
shmop_close($shm_id);

// Get the file token key
$key = ftok(__DIR__, ‘a‘);

// 创建一个共享内存
$shm_id = shm_attach($key, 1024, 777); // resource type
if ($shm_id === false) {
    die(‘Unable to create the shared memory segment‘);
}

#设置一个值
shm_put_var($shm_id, 111, ‘value‘);

#删除一个key
//shm_remove_var($shm_id, 111);

#获取一个值
$value = shm_get_var($shm_id,  111);
var_dump($value);

#检测一个key是否存在
// var_dump(shm_has_var($shm_id,  111));

#从系统中移除
shm_remove($shm_id);

#关闭和共享内存的连接
shm_detach($shm_id);

/**
* 使用共享内存和信号量实现
* 
* 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";
        echo ‘‘;
        
        echo strlen($data);
        echo ‘‘;
        
        echo $this->blockSize - 1;
        echo ‘‘;
        
        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
    }
}

/*
 * // 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);
 */