JCache concept.

cache.php

<?php
/**
 * @package     Joomla.Platform
 * @subpackage  Cache
 *
 * @copyright   Copyright (C) 2005 - 2011 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE
 */

defined('JPATH_PLATFORM') or die();

/**
 * Joomla! Caching Class
 *
 * @package     Joomla.Platform
 * @subpackage  Cache
 * @since       12.1
 */
class JCache
{
	/**
	 * @var    JRegistry  The options for the cache object.
	 * @since  12.1
	 */
	protected $options;

	/**
	 * Constructor.
	 *
	 * @param   JRegistry  $options  Caching options object.
	 *
	 * @since   12.1
	 */
	public function __construct(JRegistry $options = null)
	{
		if ($options instanceof JRegistry)
		{
			$this->options = $options;
		}
		else
		{
			$this->options = new JRegistry;
		}

		$this->options->def('dsn', 'file:///tmp/caching/');
		$this->options->def('lifetime', 900);
		$this->options->def('locking', true);
	}

	/**
	 * Get an option from the JCache instance.
	 *
	 * @param   string  $key  The name of the option to get.
	 *
	 * @return  mixed  The option value.
	 *
	 * @since   12.1
	 */
	public function getOption($key)
	{
		return $this->options->get($key);
	}

	/**
	 * Set an option for the JCache instance.
	 *
	 * @param   string  $key    The name of the option to set.
	 * @param   mixed   $value  The option value to set.
	 *
	 * @return  JCache  This object for method chaining.
	 *
	 * @since   12.1
	 */
	public function setOption($key, $value)
	{
		$this->options->set($key, $value);

		return $this;
	}

	/**
	 * Get cached data by id.  If the cached data has expired then the cached data will be removed
	 * and false will be returned.
	 *
	 * @param   string  $cacheId  The cache data id.
	 *
	 * @return  mixed  False on failure or a cached data string if it exists.
	 *
	 * @since   12.1
	 */
	public function get($cacheId)
	{
		// If the cached data has expired remove it and return false.
		if ($this->isExpired($cacheId))
		{
			$this->remove($cacheId);

			return false;
		}

		// Open the stream resource.
		$resource = fopen($this->fetchStreamUri($cacheId), 'rb');

		// If locking is enabled get a shared lock for reading on the resource.
		if ($this->options->get('locking'))
		{
			flock($resource, LOCK_SH);
		}

		// Read the data from the stream resource.
		$data = stream_get_contents($resource);

		// If locking is enabled release the lock on the resource.
		if ($this->options->get('locking'))
		{
			flock($resource, LOCK_UN);
		}

		// Tidy up behind ourselves.
		fclose($resource);

		return $data;
	}

	/**
	 * Check whether or not the cached data by id has expired.
	 *
	 * @param   string  $cacheId  The cache data id.
	 *
	 * @return  boolean  True if the data has expired.
	 *
	 * @since   12.1
	 */
	public function isExpired($cacheId)
	{
		// Check to see if the cached data has expired.
		if (filemtime($this->fetchStreamUri($cacheId)) < (time() - $this->options->get('lifetime')))
		{
			return true;
		}

		return false;
	}

	/**
	 * Store the cached data by id.
	 *
	 * @param   mixed   $data     The data to store
	 * @param   string  $cacheId  The cache data id
	 *
	 * @return  boolean  True if cache stored.
	 *
	 * @since   12.1
	 */
	public function store($data, $cacheId)
	{
		return (bool) file_put_contents(
			$this->fetchStreamUri($cacheId),
			$data,
			($this->options->get('locking') ? LOCK_EX : null)
		);
	}

	/**
	 * Remove a cached data entry by id.
	 *
	 * @param   string  $cacheId  The cache data id.
	 *
	 * @return  boolean  True on success, false otherwise
	 *
	 * @since   12.1
	 */
	public function remove($cacheId)
	{
		return unlink($this->fetchStreamUri($cacheId));
	}

	/**
	 * Remove a cached data entry by id.
	 *
	 * @param   string  $cacheId  The cache data id.
	 *
	 * @return  string  The full stream URI for the cache entry.
	 *
	 * @since   12.1
	 */
	protected function fetchStreamUri($cacheId)
	{
		return $this->options->get('dsn') . $cacheId;
	}
}