extension.cache.dbm.php

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


class getID3_cached_dbm extends getID3
{

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

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

                // Check for specific dba driver
                if (!function_exists('dba_handlers') || !in_array($cache_type, dba_handlers())) {
                        throw new Exception('PHP is not compiled --with '.$cache_type.' support, required to use DBM style cache.');
                }

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

                // Open lock file for writing
                if (!is_writeable($lock_filename)) {
                        throw new Exception('lock file: '.$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)) {
                                throw new Exception('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 (!$this->dba) {
                                throw new Exception('failed to create dbm file: '.$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::__construct();
        }



        // public: destructor
        public 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
        public 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 (!$this->dba) {
                        throw new Exception('failed to clear cache/recreate dbm file: '.$this->dbm_filename);
                }

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

                // Re-register shutdown function
                register_shutdown_function(array($this, '__destruct'));
        }



        // public: analyze file
        public 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;
        }

}