DomFramework/lockfile.php

<?php
/** DomFramework
    @package domframework
    @author Dominique Fournier <dominique@fournier38.fr> */

/** The lock management of files */
class lockfile
{
  /** The Exclusive lock file */
  public $storagelock = "./data/lockfile.lock";
  /** The Read-Only lock file */
  private $storagelockRO = FALSE;

  /** This function lock the storage file until all is written.
      If an other processus want to lock, it hang until the lock is released */
  public function lockRW ()
  {
    if (!is_dir (dirname ($this->storagelock)))
      @mkdir (dirname ($this->storagelock));
    if (!is_dir (dirname ($this->storagelock)))
      throw new Exception ("Can't create '".dirname ($this->storagelock)."'",
                           500);
    $lockid = uniqid() . '_' . md5 (mt_rand());
    $startTime = microtime (TRUE);
    // Stale lock : 60s old min
    if (file_exists ($this->storagelock) &&
        filemtime ($this->storagelock) < time() - 60)
    {
      // TODO : Log the Stale lock removing
      unlink ($this->storagelock);
    }

    // Wait RW Lock
    while (1)
    {
      while (file_exists ($this->storagelock))
      {
        usleep (100000);
        clearstatcache (TRUE, $this->storagelock);
        if (microtime (TRUE) > $startTime + 10)
          throw new Exception ("Can't have the authorization lock RW in 10s",
                               500);
      }

      file_put_contents ($this->storagelock, $lockid, FILE_APPEND);
      clearstatcache (TRUE, $this->storagelock);
      $cnt = file_get_contents ($this->storagelock);
      if (substr ($cnt, 0, strlen ($lockid)) === $lockid)
        break;
    }

    // Wait all the RO lock to go away
    $startTime = microtime (TRUE);
    while (count (glob ($this->storagelock."-*")) > 0)
    {
      usleep (100000);
      if (microtime (TRUE) > $startTime + 10)
        throw new Exception ("Can't have the authorization lock RO in 10s",
                             500);
    }

    // I have the lock and no RO lock !
    return TRUE;
  }

  /** This function lock the storage in share mode (to read the file without
      modification at the same time) */
  public function lockRO ()
  {
    if (!is_dir (dirname ($this->storagelock)))
      @mkdir (dirname ($this->storagelock));
    if (!is_dir (dirname ($this->storagelock)))
      throw new Exception ("Can't create '".dirname ($this->storagelock)."'",
                           500);
    $lockid = uniqid() . '_' . md5 (mt_rand());
    // Stale lock : 60s old min
    if (file_exists ($this->storagelock) &&
        filemtime ($this->storagelock) < time() - 60)
    {
      // TODO : Log the Stale lock removing
      unlink ($this->storagelock);
    }

    // wait the removing of lockRW
    $startTime = microtime (TRUE);
    while (file_exists ($this->storagelock))
    {
      usleep (100000);
      clearstatcache (TRUE, $this->storagelock);
      if (microtime (TRUE) > $startTime + 10)
        throw new Exception ("Can't have the authorization lock in 10s", 500);
    }

    touch ($this->storagelock."-".$lockid);
    $this->storagelockRO = $this->storagelock."-".$lockid;
  }

  /** This function unlock RW the storage file */
  public function unlockRW ()
  {
    if (file_exists ($this->storagelock))
      unlink ($this->storagelock);
  }

  /** This function unlock RO the storage file */
  public function unlockRO ()
  {
    if ($this->storagelockRO !== FALSE && file_exists ($this->storagelockRO))
      unlink ($this->storagelockRO);
  }
}