PHP shared memory usage example analysis, PHP shared example analysis_PHP tutorial

PHP shared memory usage example analysis, PHP shared memory example analysis

The examples in this article describe the usage of PHP shared memory. Share it with everyone for your reference, the details are as follows:

Shared memory is mainly used for inter-process communication

There are two sets of extensions for shared memory in php

1. shmop needs to be enabled when compiling --enable-shmop parameter

Example:

$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);

2. Use the sem class function in the Semaphore extension (more convenient to use, similar to key-value format)

// 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);

Note: These two methods are not universal

A message queue implemented using shared memory and semaphores

/**
* 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);
 */

Use the ipc command to view under Linux, and use the ipcrm command to delete

Readers who are interested in more PHP-related content can check out the special topics of this site: "Introduction Tutorial on PHP Basic Syntax", "Summary of PHP Error and Exception Handling Methods", "Summary of PHP Programming Algorithms" and "php Object-Oriented Programming" Design introductory tutorial》

I hope this article will be helpful to everyone in PHP programming.

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