2 files changed, 287 insertions, 0 deletions
diff --git a/phpBB/phpbb/lock/db.php b/phpBB/phpbb/lock/db.php
new file mode 100644
index 0000000000..85ba9a7aa3
--- /dev/null
+++ b/phpBB/phpbb/lock/db.php
@@ -0,0 +1,146 @@
+<?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;
+
+/**
+* Database locking class
+*/
+class db
+{
+	/**
+	* Name of the config variable this lock uses
+	* @var string
+	*/
+	private $config_name;
+
+	/**
+	* Unique identifier for this lock.
+	*
+	* @var string
+	*/
+	private $unique_id;
+
+	/**
+	* Stores the state of this lock
+	* @var bool
+	*/
+	private $locked;
+
+	/**
+	* The phpBB configuration
+	* @var \phpbb\config\config
+	*/
+	private $config;
+
+	/**
+	* A database connection
+	* @var \phpbb\db\driver\driver_interface
+	*/
+	private $db;
+
+	/**
+	* Creates a named released instance of the lock.
+	*
+	* You have to call acquire() to actually create the lock.
+	*
+	* @param	string								$config_name	A config variable to be used for locking
+	* @param	\phpbb\config\config				$config			The phpBB configuration
+	* @param	\phpbb\db\driver\driver_interface	$db				A database connection
+	*/
+	public function __construct($config_name, \phpbb\config\config $config, \phpbb\db\driver\driver_interface $db)
+	{
+		$this->config_name = $config_name;
+		$this->config = $config;
+		$this->db = $db;
+	}
+
+	/**
+	* Tries to acquire the lock by updating
+	* the configuration variable in the database.
+	*
+	* As a lock may only be held by one process at a time, lock
+	* acquisition may fail if another process is holding the lock
+	* or if another process obtained the lock but never released it.
+	* Locks are forcibly released after a timeout of 1 hour.
+	*
+	* @return	bool			true if lock was acquired
+	*							false otherwise
+	*/
+	public function acquire()
+	{
+		if ($this->locked)
+		{
+			return false;
+		}
+
+		if (!isset($this->config[$this->config_name]))
+		{
+			$this->config->set($this->config_name, '0', false);
+		}
+		$lock_value = $this->config[$this->config_name];
+
+		// make sure lock cannot be acquired by multiple processes
+		if ($lock_value)
+		{
+			// if the other process is running more than an hour already we have to assume it
+			// aborted without cleaning the lock
+			$time = explode(' ', $lock_value);
+			$time = $time[0];
+
+			if ($time + 3600 >= time())
+			{
+				return false;
+			}
+		}
+
+		$this->unique_id = time() . ' ' . unique_id();
+
+		// try to update the config value, if it was already modified by another
+		// process we failed to acquire the lock.
+		$this->locked = $this->config->set_atomic($this->config_name, $lock_value, $this->unique_id, false);
+
+		return $this->locked;
+	}
+
+	/**
+	* Does this process own the lock?
+	*
+	* @return	bool			true if lock is owned
+	*							false otherwise
+	*/
+	public function owns_lock()
+	{
+		return (bool) $this->locked;
+	}
+
+	/**
+	* Releases the lock.
+	*
+	* The lock must have been previously obtained, that is, acquire() call
+	* was issued and returned true.
+	*
+	* Note: Attempting to release a lock that is already released,
+	* that is, calling release() multiple times, is harmless.
+	*
+	* @return null
+	*/
+	public function release()
+	{
+		if ($this->locked)
+		{
+			$this->config->set_atomic($this->config_name, $this->unique_id, '0', false);
+			$this->locked = false;
+		}
+	}
+}
diff --git a/phpBB/phpbb/lock/flock.php b/phpBB/phpbb/lock/flock.php
new file mode 100644
index 0000000000..df88e1490a
--- /dev/null
+++ b/phpBB/phpbb/lock/flock.php
@@ -0,0 +1,141 @@
+<?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;
+		}
+	}
+}