source: extensions/charlies_content/getid3/getid3/extension.cache.dbm.php @ 3544

<?php
/////////////////////////////////////////////////////////////////
/// getID3() by James Heinrich <info@getid3.org>               //
//  available at http://getid3.sourceforge.net                 //
//            or http://www.getid3.org                         //
/////////////////////////////////////////////////////////////////
//                                                             //
// extension.cache.dbm.php - part of getID3()                  //
// Please see readme.txt for more information                  //
//                                                            ///
/////////////////////////////////////////////////////////////////
//                                                             //
// This extension written by Allan Hansen <ahØartemis*dk>      //
//                                                            ///
/////////////////////////////////////////////////////////////////


/**
* This is a caching extension for getID3(). It works the exact same
* way as the getID3 class, but return cached information very fast
*
* Example:
*
*    Normal getID3 usage (example):
*
*       require_once 'getid3/getid3.php';
*       $getID3 = new getID3;
*       $getID3->encoding = 'UTF-8';
*       $info1 = $getID3->analyze('file1.flac');
*       $info2 = $getID3->analyze('file2.wv');
*
*    getID3_cached usage:
*
*       require_once 'getid3/getid3.php';
*       require_once 'getid3/getid3/extension.cache.dbm.php';
*       $getID3 = new getID3_cached('db3', '/tmp/getid3_cache.dbm',
*                                          '/tmp/getid3_cache.lock');
*       $getID3->encoding = 'UTF-8';
*       $info1 = $getID3->analyze('file1.flac');
*       $info2 = $getID3->analyze('file2.wv');
*
*
* Supported Cache Types
*
*   SQL Databases:          (use extension.cache.mysql)
*
*   cache_type          cache_options
*   -------------------------------------------------------------------
*   mysql               host, database, username, password
*
*
*   DBM-Style Databases:    (this extension)
*
*   cache_type          cache_options
*   -------------------------------------------------------------------
*   gdbm                dbm_filename, lock_filename
*   ndbm                dbm_filename, lock_filename
*   db2                 dbm_filename, lock_filename
*   db3                 dbm_filename, lock_filename
*   db4                 dbm_filename, lock_filename  (PHP5 required)
*
*   PHP must have write access to both dbm_filename and lock_filename.
*
*
* Recommended Cache Types
*
*   Infrequent updates, many reads      any DBM
*   Frequent updates                    mysql
*/


class getID3_cached_dbm extends getID3
{

        // public: constructor - see top of this file for cache type and cache_options
        function getID3_cached_dbm($cache_type, $dbm_filename, $lock_filename) {

                // Check for dba extension
                if (!extension_loaded('dba')) {
                        die('PHP is not compiled with dba support, required to use DBM style cache.');
                }

                // Check for specific dba driver
                if (function_exists('dba_handlers')) {  // PHP 4.3.0+
                        if (!in_array('db3', dba_handlers())) {
                                die('PHP is not compiled --with '.$cache_type.' support, required to use DBM style cache.');
                        }
                }
                else { // PHP <= 4.2.3
                        ob_start(); // nasty, buy the only way to check...
                        phpinfo();
                        $contents = ob_get_contents();
                        ob_end_clean();
                        if (!strstr($contents, $cache_type)) {
                                die('PHP is not compiled --with '.$cache_type.' support, required to use DBM style cache.');
                        }
                }

                // Create lock file if needed
                if (!file_exists($lock_filename)) {
                        if (!touch($lock_filename)) {
                                die('failed to create lock file: ' . $lock_filename);
                        }
                }

                // Open lock file for writing
                if (!is_writeable($lock_filename)) {
                        die('lock file: ' . $lock_filename . ' is not writable');
                }
                $this->lock = fopen($lock_filename, 'w');

                // Acquire exclusive write lock to lock file
                flock($this->lock, LOCK_EX);

                // Create dbm-file if needed
                if (!file_exists($dbm_filename)) {
                        if (!touch($dbm_filename)) {
                                die('failed to create dbm file: ' . $dbm_filename);
                        }
                }

                // Try to open dbm file for writing
                $this->dba = @dba_open($dbm_filename, 'w', $cache_type);
                if (!$this->dba) {

                        // Failed - create new dbm file
                        $this->dba = dba_open($dbm_filename, 'n', $cache_type);

                        if (!$this->dba) {
                                die('failed to create dbm file: ' . $dbm_filename);
                        }

                        // Insert getID3 version number
                        dba_insert(GETID3_VERSION, GETID3_VERSION, $this->dba);
                }

                // Init misc values
                $this->cache_type   = $cache_type;
                $this->dbm_filename = $dbm_filename;

                // Register destructor
                register_shutdown_function(array($this, '__destruct'));

                // Check version number and clear cache if changed
                if (dba_fetch(GETID3_VERSION, $this->dba) != GETID3_VERSION) {
                        $this->clear_cache();
                }

                parent::getID3();
        }



        // public: destuctor
        function __destruct() {

                // Close dbm file
                @dba_close($this->dba);

                // Release exclusive lock
                @flock($this->lock, LOCK_UN);

                // Close lock file
                @fclose($this->lock);
        }



        // public: clear cache
        function clear_cache() {

                // Close dbm file
                dba_close($this->dba);

                // Create new dbm file
                $this->dba = dba_open($this->dbm_filename, 'n', $this->cache_type);

                if (!$this->dba) {
                        die('failed to clear cache/recreate dbm file: ' . $this->dbm_filename);
                }

                // Insert getID3 version number
                dba_insert(GETID3_VERSION, GETID3_VERSION, $this->dba);

                // Reregister shutdown function
                register_shutdown_function(array($this, '__destruct'));
        }



        // public: analyze file
        function analyze($filename) {

                if (file_exists($filename)) {

                        // Calc key     filename::mod_time::size    - should be unique
                        $key = $filename . '::' . filemtime($filename) . '::' . filesize($filename);

                        // Loopup key
                        $result = dba_fetch($key, $this->dba);

                        // Hit
                        if ($result !== false) {
                                return unserialize($result);
                        }
                }

                // Miss
                $result = parent::analyze($filename);

                // Save result
                if (file_exists($filename)) {
                        dba_insert($key, serialize($result), $this->dba);
                }

                return $result;
        }

}


?>