fastdfs_get_last_error_no(), 'info' => fastdfs_get_last_error_info(), 'act' => $act)
    
    private static $instance = null;
    
    private function __construct(){
        return true;
    }
    
    public function __destruct(){
        fastdfs_tracker_close_all_connections();
    }
 
    public static function getInstance( $group_name = '' ){
        if (self::$instance == null){
            self::$instance = new FDFS();
            
            if( !self::$instance->_loadTracker() ){
                return false;
            }
        }
        
        return self::$instance;
    }
    
    private function _loadTracker(){
        $this->_tracker = fastdfs_tracker_get_connection();
        if( !$this->_tracker ){
            return false;
        }
        if( !fastdfs_active_test($this->_tracker) ){
            $this->_setLastError('fastdfs_active_test(_tracker)');
            return false;
        }
        
        return true;
    }
    
    private function _setLastError( $act = '' ){
        $this->_error = array('no' => fastdfs_get_last_error_no(), 'info' => fastdfs_get_last_error_info(), 'act' => $act);
    }
    
    /**
     * 连接storage
     * @param string $group_name
     * @return boolean
     */
    public function storageConnection($group_name = ''){
        if( !isset($this->_storage_arr[$group_name]) ){
            $this->_storage_arr[$group_name] = fastdfs_tracker_query_storage_store($group_name, $this->_tracker);
            if( !$this->_storage_arr[$group_name] ){
                return false;
            }
    
            $server = fastdfs_connect_server($this->_storage_arr[$group_name]['ip_addr'], $this->_storage_arr[$group_name]['port']);
            if( !$server ){
                $this->_setLastError('fastdfs_connect_server(_storage)');
                return false;
            }
    
            if( !fastdfs_active_test($server) ){
                $this->_setLastError('fastdfs_active_test(server)');
                return false;
            }
            $this->_storage_arr[$group_name]['sock'] = $server['sock'];
            unset($server);
        }
    
        if( !isset($this->_storage_arr[$group_name]) ){
            $this->_group_name    = null;
            $this->_storage       = null;
            return false;
        }else{
            $this->_group_name    = $group_name;
            $this->_storage       = &$this->_storage_arr[$group_name];
        }
    
        return true;
    }
    
    /**
     * 上传文件
     * @param string $local_filename 本地文件路径
     * @param boolean $file_ext_name 文件后缀名
     * @param boolean $is_file_buff 是否是字符内容
     * @return boolean|array array('group_name' => '', 'filename' => '')
     */
    public function upload( $local_filename, $file_ext_name = null, $is_file_buff = false ){
        if($is_file_buff){
            $act = 'fastdfs_storage_upload_by_filebuff';
        }else{
            $act = 'fastdfs_storage_upload_by_filename';
        }
        $file_info = $act($local_filename, $file_ext_name, array(), null, $this->_tracker, $this->_storage);
        if( !$file_info ){
            $this->_setLastError($act.'('.$local_filename.')');
            return false;
        }
        
        return $file_info;
    }
    
    /**
     * 上传从文件
     * @param string $local_filename  本地文件路径
     * @param string $master_filename storage里的主文件路径
     * @param string $prefix_name 后缀
     * @param boolean $file_ext_name 文件后缀名
     * @param boolean $is_file_buff 是否是字符内容
     * @return boolean|array  array('group_name' => '', 'filename' => '')
     */
    public function uploadSlave( $local_filename, $master_filename, $prefix_name, $file_ext_name = null, $is_file_buff = false ){
        if($is_file_buff){
            $act = 'fastdfs_storage_upload_slave_by_filebuff';
        }else{
            $act = 'fastdfs_storage_upload_slave_by_filename';
        }
        $file_info = $act($local_filename, $this->_group_name, $master_filename, $prefix_name, $file_ext_name, array(), $this->_tracker, $this->_storage);
        if( !$file_info ){
            $this->_setLastError($act.'('.$local_filename.','.$master_filename.','.$prefix_name.')');
            return false;
        }
        
        return $file_info;
    }
    
    /**
     * 删除文件
     * @param string $group_name
     * @param string $filename
     */
    public function delete($group_name, $filename){
        return fastdfs_storage_delete_file($group_name, $filename);
    }
    
    /**
     * 下载文件
     * @param string $group_name
     * @param string $filename
     */
    public function down($group_name, $filename){
        $file_content = fastdfs_storage_download_file_to_buff($group_name, $filename);
        return $file_content;
    }
    
    public function exist($group_name, $filename){
        return fastdfs_storage_file_exist($group_name, $filename);
    }
    
    /**
     * 获取最后的错误信息
     */
    public function lastError(){
        if( !$this->_error ){
            $this->__setLastError();
        }
        return $this->_error;
    }
}
?>