source: sourcecode/system/database/DB_cache.php @ 1

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 5.1.6 or newer
 *
 * @package             CodeIgniter
 * @author              ExpressionEngine Dev Team
 * @copyright   Copyright (c) 2008 - 2011, EllisLab, Inc.
 * @license             http://codeigniter.com/user_guide/license.html
 * @link                http://codeigniter.com
 * @since               Version 1.0
 * @filesource
 */

// ------------------------------------------------------------------------

/**
 * Database Cache Class
 *
 * @category    Database
 * @author              ExpressionEngine Dev Team
 * @link                http://codeigniter.com/user_guide/database/
 */
class CI_DB_Cache {

        var $CI;
        var $db;        // allows passing of db object so that multiple database connections and returned db objects can be supported

        /**
         * Constructor
         *
         * Grabs the CI super object instance so we can access it.
         *
         */
        function __construct(&$db)
        {
                // Assign the main CI object to $this->CI
                // and load the file helper since we use it a lot
                $this->CI =& get_instance();
                $this->db =& $db;
                $this->CI->load->helper('file');
        }

        // --------------------------------------------------------------------

        /**
         * Set Cache Directory Path
         *
         * @access      public
         * @param       string  the path to the cache directory
         * @return      bool
         */
        function check_path($path = '')
        {
                if ($path == '')
                {
                        if ($this->db->cachedir == '')
                        {
                                return $this->db->cache_off();
                        }

                        $path = $this->db->cachedir;
                }

                // Add a trailing slash to the path if needed
                $path = preg_replace("/(.+?)\/*$/", "\\1/",  $path);

                if ( ! is_dir($path) OR ! is_really_writable($path))
                {
                        // If the path is wrong we'll turn off caching
                        return $this->db->cache_off();
                }

                $this->db->cachedir = $path;
                return TRUE;
        }

        // --------------------------------------------------------------------

        /**
         * Retrieve a cached query
         *
         * The URI being requested will become the name of the cache sub-folder.
         * An MD5 hash of the SQL statement will become the cache file name
         *
         * @access      public
         * @return      string
         */
        function read($sql)
        {
                if ( ! $this->check_path())
                {
                        return $this->db->cache_off();
                }

                $segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);

                $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);

                $filepath = $this->db->cachedir.$segment_one.'+'.$segment_two.'/'.md5($sql);

                if (FALSE === ($cachedata = read_file($filepath)))
                {
                        return FALSE;
                }

                return unserialize($cachedata);
        }

        // --------------------------------------------------------------------

        /**
         * Write a query to a cache file
         *
         * @access      public
         * @return      bool
         */
        function write($sql, $object)
        {
                if ( ! $this->check_path())
                {
                        return $this->db->cache_off();
                }

                $segment_one = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);

                $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);

                $dir_path = $this->db->cachedir.$segment_one.'+'.$segment_two.'/';

                $filename = md5($sql);

                if ( ! @is_dir($dir_path))
                {
                        if ( ! @mkdir($dir_path, DIR_WRITE_MODE))
                        {
                                return FALSE;
                        }

                        @chmod($dir_path, DIR_WRITE_MODE);
                }

                if (write_file($dir_path.$filename, serialize($object)) === FALSE)
                {
                        return FALSE;
                }

                @chmod($dir_path.$filename, FILE_WRITE_MODE);
                return TRUE;
        }

        // --------------------------------------------------------------------

        /**
         * Delete cache files within a particular directory
         *
         * @access      public
         * @return      bool
         */
        function delete($segment_one = '', $segment_two = '')
        {
                if ($segment_one == '')
                {
                        $segment_one  = ($this->CI->uri->segment(1) == FALSE) ? 'default' : $this->CI->uri->segment(1);
                }

                if ($segment_two == '')
                {
                        $segment_two = ($this->CI->uri->segment(2) == FALSE) ? 'index' : $this->CI->uri->segment(2);
                }

                $dir_path = $this->db->cachedir.$segment_one.'+'.$segment_two.'/';

                delete_files($dir_path, TRUE);
        }

        // --------------------------------------------------------------------

        /**
         * Delete all existing cache files
         *
         * @access      public
         * @return      bool
         */
        function delete_all()
        {
                delete_files($this->db->cachedir, TRUE);
        }

}


/* End of file DB_cache.php */
/* Location: ./system/database/DB_cache.php */