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139 lines
2.8 KiB
PHP
139 lines
2.8 KiB
PHP
<?php
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/**
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*
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* @package phpBB3
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* @copyright (c) 2012 phpBB Group
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* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
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*
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*/
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namespace phpbb\lock;
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/**
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* File locking class
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* @package phpBB3
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*/
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class flock
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{
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/**
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* Path to the file to which access is controlled
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*
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* @var string
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*/
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private $path;
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/**
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* File pointer for the lock file
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* @var string
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*/
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private $lock_fp;
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/**
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* Constructor.
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*
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* You have to call acquire() to actually acquire the lock.
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*
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* @param string $path Path to the file to which access is controlled
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*/
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public function __construct($path)
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{
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$this->path = $path;
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$this->lock_fp = null;
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}
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/**
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* Tries to acquire the lock.
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*
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* If the lock is already held by another process, this call will block
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* until the other process releases the lock. If a lock is acquired and
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* is not released before script finishes but the process continues to
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* live (apache/fastcgi) then subsequent processes trying to acquire
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* the same lock will be blocked forever.
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*
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* If the lock is already held by the same process via another instance
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* of this class, this call will block forever.
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*
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* If flock function is disabled in php or fails to work, lock
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* acquisition will fail and false will be returned.
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*
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* @return bool true if lock was acquired
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* false otherwise
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*/
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public function acquire()
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{
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if ($this->lock_fp)
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{
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return false;
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}
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// For systems that can't have two processes opening
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// one file for writing simultaneously
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if (file_exists($this->path . '.lock'))
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{
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$mode = 'rb';
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}
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else
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{
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$mode = 'wb';
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}
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$this->lock_fp = @fopen($this->path . '.lock', $mode);
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if ($mode == 'wb')
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{
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if (!$this->lock_fp)
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{
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// Two processes may attempt to create lock file at the same time.
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// Have the losing process try opening the lock file again for reading
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// on the assumption that the winning process created it
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$mode = 'rb';
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$this->lock_fp = @fopen($this->path . '.lock', $mode);
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}
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else
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{
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// Only need to set mode when the lock file is written
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@chmod($this->path . '.lock', 0666);
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}
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}
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if ($this->lock_fp)
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{
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@flock($this->lock_fp, LOCK_EX);
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}
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return (bool) $this->lock_fp;
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}
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/**
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* Does this process own the lock?
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*
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* @return bool true if lock is owned
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* false otherwise
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*/
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public function owns_lock()
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{
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return (bool) $this->lock_fp;
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}
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/**
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* Releases the lock.
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*
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* The lock must have been previously obtained, that is, acquire() call
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* was issued and returned true.
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*
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* Note: Attempting to release a lock that is already released,
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* that is, calling release() multiple times, is harmless.
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*
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* @return null
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*/
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public function release()
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{
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if ($this->lock_fp)
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{
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@flock($this->lock_fp, LOCK_UN);
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fclose($this->lock_fp);
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$this->lock_fp = null;
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}
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}
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}
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