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msd2/phpBB3/phpbb/lock/flock.php

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+<?php
+/**
+*
+* This file is part of the phpBB Forum Software package.
+*
+* @copyright (c) phpBB Limited <https://www.phpbb.com>
+* @license GNU General Public License, version 2 (GPL-2.0)
+*
+* For full copyright and license information, please see
+* the docs/CREDITS.txt file.
+*
+*/
+
+namespace phpbb\lock;
+
+/**
+* File locking class
+*/
+class flock
+{
+	/**
+	* Path to the file to which access is controlled
+	*
+	* @var string
+	*/
+	private $path;
+
+	/**
+	* File pointer for the lock file
+	* @var string
+	*/
+	private $lock_fp;
+
+	/**
+	* Constructor.
+	*
+	* You have to call acquire() to actually acquire the lock.
+	*
+	* @param	string	$path	Path to the file to which access is controlled
+	*/
+	public function __construct($path)
+	{
+		$this->path = $path;
+		$this->lock_fp = null;
+	}
+
+	/**
+	* Tries to acquire the lock.
+	*
+	* If the lock is already held by another process, this call will block
+	* until the other process releases the lock. If a lock is acquired and
+	* is not released before script finishes but the process continues to
+	* live (apache/fastcgi) then subsequent processes trying to acquire
+	* the same lock will be blocked forever.
+	*
+	* If the lock is already held by the same process via another instance
+	* of this class, this call will block forever.
+	*
+	* If flock function is disabled in php or fails to work, lock
+	* acquisition will fail and false will be returned.
+	*
+	* @return	bool			true if lock was acquired
+	*							false otherwise
+	*/
+	public function acquire()
+	{
+		if ($this->lock_fp)
+		{
+			return false;
+		}
+
+		// For systems that can't have two processes opening
+		// one file for writing simultaneously
+		if (file_exists($this->path . '.lock'))
+		{
+			$mode = 'rb';
+		}
+		else
+		{
+			$mode = 'wb';
+		}
+
+		$this->lock_fp = @fopen($this->path . '.lock', $mode);
+
+		if ($mode == 'wb')
+		{
+			if (!$this->lock_fp)
+			{
+				// Two processes may attempt to create lock file at the same time.
+				// Have the losing process try opening the lock file again for reading
+				// on the assumption that the winning process created it
+				$mode = 'rb';
+				$this->lock_fp = @fopen($this->path . '.lock', $mode);
+			}
+			else
+			{
+				// Only need to set mode when the lock file is written
+				@chmod($this->path . '.lock', 0666);
+			}
+		}
+
+		if ($this->lock_fp)
+		{
+			@flock($this->lock_fp, LOCK_EX);
+		}
+
+		return (bool) $this->lock_fp;
+	}
+
+	/**
+	* Does this process own the lock?
+	*
+	* @return	bool			true if lock is owned
+	*							false otherwise
+	*/
+	public function owns_lock()
+	{
+		return (bool) $this->lock_fp;
+	}
+
+	/**
+	* Releases the lock.
+	*
+	* The lock must have been previously obtained, that is, acquire() call
+	* was issued and returned true.
+	*
+	* Note: Attempting to release a lock that is already released,
+	* that is, calling release() multiple times, is harmless.
+	*
+	* @return null
+	*/
+	public function release()
+	{
+		if ($this->lock_fp)
+		{
+			@flock($this->lock_fp, LOCK_UN);
+			fclose($this->lock_fp);
+			$this->lock_fp = null;
+		}
+	}
+}