PHP implementation read memory sequence number, PHP read memory sequence _php tutorial

PHP implementation read memory sequence number, PHP read memory order

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semWrapper.class.php

/* Signal Volume (Semaphore). * This is a wrapper class that addresses different implementations of "semaphores" under different platforms. * This class is only symbolic at the moment, and it is actually an empty run under the Windows platform (and does not really implement mutexes). */class semwrapper{  private $hasSemSupport;  Private $sem;  Const SEM_KEY = 1;   Public function __construct ()  {    $this->hassemsupport = function_exists (' Sem_get ');    if ($this->hassemsupport) {      $this->sem = Sem_get (Self::sem_key);    }  }   Public function Acquire () {    if ($this->hassemsupport) {      return Sem_acquire ($this->sem);    }    return true;  }   Public Function release () {    if ($this->hassemsupport) {      return sem_release ($this->sem);    }    return true;  }}

SeqGenerator.class.php

/* * Sequential number generator.   */class seqgenerator{Const SHM_KEY = 1;   /** * Initialize the sequence number generator.   * Only the first call after server startup is valid, and calling this method after this does not actually work.   * @param int $start The starting value of the sequence number.   * @return Boolean returns true to indicate success.    */static Public function init ($start = 1) {//mutual exclusion via semaphores, avoid access violation of shared memory $SW = new Semwrapper;    if (! $SW->acquire ()) {return false;    }//Open shared memory $shm _id = Shmop_open (Self::shm_key, ' n ', 0644, 4);      if (Empty ($shm _id)) {//due to the use of ' n ' mode, if the shared memory cannot be opened, you can assume that the shared memory has been created without having to initialize the $SW->release () again;    return true;    }//write the initial value in shared memory $size = Shmop_write ($shm _id, pack (' L ', $start), 0);      if ($size! = 4) {shmop_close ($shm _id);      $SW->release ();    return false;    }//Close shared memory, release semaphore Shmop_close ($shm _id);    $SW->release ();  return true;   }/** * produces the next sequential number.    * The order number generated by the @return int */static public function next () {//is mutually exclusive through semaphores to avoid access violation of shared memory $SW = new Semwrapper;    if (! $SW->acquire ()) {return 0; }     //Open Shared memory $shm _id = Shmop_open (Self::shm_key, ' W ', 0, 0);      if (Empty ($shm _id)) {$SW->release ();    return 0;    }//reads the sequence number from the shared memory $data = Shmop_read ($shm _id, 0, 4);      if (empty ($data)) {$SW->release ();    return 0;    } $arr = Unpack (' L ', $data);     $seq = $arr [1];    Write the next sequence number to the shared memory $size = Shmop_write ($shm _id, pack (' L ', $seq + 1), 0);      if ($size! = 4) {$SW->release ();    return 0;    }//Close shared memory, release semaphore Shmop_close ($shm _id);    $SW->release ();  return $seq; }}

page.php

Use method $seq = Seqgenerator::next (); Var_dump ($SEQ);

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