bcit-ci/CodeIgniter

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system/core/Loader.php

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<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package    CodeIgniter
 * @author    EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
 * @license    https://opensource.org/licenses/MIT    MIT License
 * @link    https://codeigniter.com
 * @since    Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Loader Class
 *
 * Loads framework components.
 *
 * @package        CodeIgniter
 * @subpackage    Libraries
 * @category    Loader
 * @author        EllisLab Dev Team
 * @link        https://codeigniter.com/user_guide/libraries/loader.html
 */
class CI_Loader {

    // All these are set automatically. Don't mess with them.
    /**
     * Nesting level of the output buffering mechanism
     *
     * @var    int
     */
    protected $_ci_ob_level;

    /**
     * List of paths to load views from
     *
     * @var    array
     */
    protected $_ci_view_paths =    array(VIEWPATH    => TRUE);

    /**
     * List of paths to load libraries from
     *
     * @var    array
     */
    protected $_ci_library_paths =    array(APPPATH, BASEPATH);

    /**
     * List of paths to load models from
     *
     * @var    array
     */
    protected $_ci_model_paths =    array(APPPATH);

    /**
     * List of paths to load helpers from
     *
     * @var    array
     */
    protected $_ci_helper_paths =    array(APPPATH, BASEPATH);

    /**
     * List of cached variables
     *
     * @var    array
     */
    protected $_ci_cached_vars =    array();

    /**
     * List of loaded classes
     *
     * @var    array
     */
    protected $_ci_classes =    array();

    /**
     * List of loaded models
     *
     * @var    array
     */
    protected $_ci_models =    array();

    /**
     * List of loaded helpers
     *
     * @var    array
     */
    protected $_ci_helpers =    array();

    /**
     * List of class name mappings
     *
     * @var    array
     */
    protected $_ci_varmap =    array(
        'unit_test' => 'unit',
        'user_agent' => 'agent'
    );

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

    /**
     * Class constructor
     *
     * Sets component load paths, gets the initial output buffering level.
     *
     * @return    void
     */
    public function __construct()
    {
        $this->_ci_ob_level = ob_get_level();
        $this->_ci_classes =& is_loaded();

        log_message('info', 'Loader Class Initialized');
    }

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

    /**
     * Initializer
     *
     * @todo    Figure out a way to move this to the constructor
     *        without breaking *package_path*() methods.
     * @uses    CI_Loader::_ci_autoloader()
     * @used-by    CI_Controller::__construct()
     * @return    void
     */
    public function initialize()
    {
        $this->_ci_autoloader();
    }

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

    /**
     * Is Loaded
     *
     * A utility method to test if a class is in the self::$_ci_classes array.
     *
     * @used-by    Mainly used by Form Helper function _get_validation_object().
     *
     * @param     string        $class    Class name to check for
     * @return     string|bool    Class object name if loaded or FALSE
     */
    public function is_loaded($class)
    {
        return array_search(ucfirst($class), $this->_ci_classes, TRUE);
    }

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

    /**
     * Library Loader
     *
     * Loads and instantiates libraries.
     * Designed to be called from application controllers.
     *
     * @param    mixed    $library    Library name
     * @param    array    $params        Optional parameters to pass to the library class constructor
     * @param    string    $object_name    An optional object name to assign to
     * @return    object
     */
    public function library($library, $params = NULL, $object_name = NULL)
    {
        if (empty($library))
        {
            return $this;
        }
        elseif (is_array($library))
        {
            foreach ($library as $key => $value)
            {
                if (is_int($key))
                {
                    $this->library($value, $params);
                }
                else
                {
                    $this->library($key, $params, $value);
                }
            }

            return $this;
        }

        if ($params !== NULL && ! is_array($params))
        {
            $params = NULL;
        }

        $this->_ci_load_library($library, $params, $object_name);
        return $this;
    }

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

    /**
     * Model Loader
     *
     * Loads and instantiates models.
     *
     * @param    mixed    $model        Model name
     * @param    string    $name        An optional object name to assign to
     * @param    bool    $db_conn    An optional database connection configuration to initialize
     * @return    object
     */
    public function model($model, $name = '', $db_conn = FALSE)
    {
        if (empty($model))
        {
            return $this;
        }
        elseif (is_array($model))
        {
            foreach ($model as $key => $value)
            {
                is_int($key) ? $this->model($value, '', $db_conn) : $this->model($key, $value, $db_conn);
            }

            return $this;
        }

        $path = '';

        // Is the model in a sub-folder? If so, parse out the filename and path.
        if (($last_slash = strrpos($model, '/')) !== FALSE)
        {
            // The path is in front of the last slash
            $path = substr($model, 0, ++$last_slash);

            // And the model name behind it
            $model = substr($model, $last_slash);
        }

        if (empty($name))
        {
            $name = $model;
        }

        if (in_array($name, $this->_ci_models, TRUE))
        {
            return $this;
        }

        $CI =& get_instance();
        if (isset($CI->$name))
        {
            throw new RuntimeException('The model name you are loading is the name of a resource that is already being used: '.$name);
        }

        if ($db_conn !== FALSE && ! class_exists('CI_DB', FALSE))
        {
            if ($db_conn === TRUE)
            {
                $db_conn = '';
            }

            $this->database($db_conn, FALSE, TRUE);
        }

        // Note: All of the code under this condition used to be just:
        //
        //       load_class('Model', 'core');
        //
        //       However, load_class() instantiates classes
        //       to cache them for later use and that prevents
        //       MY_Model from being an abstract class and is
        //       sub-optimal otherwise anyway.
        if ( ! class_exists('CI_Model', FALSE))
        {
            $app_path = APPPATH.'core'.DIRECTORY_SEPARATOR;
            if (file_exists($app_path.'Model.php'))
            {
                require_once($app_path.'Model.php');
                if ( ! class_exists('CI_Model', FALSE))
                {
                    throw new RuntimeException($app_path."Model.php exists, but doesn't declare class CI_Model");
                }

                log_message('info', 'CI_Model class loaded');
            }
            elseif ( ! class_exists('CI_Model', FALSE))
            {
                require_once(BASEPATH.'core'.DIRECTORY_SEPARATOR.'Model.php');
            }

            $class = config_item('subclass_prefix').'Model';
            if (file_exists($app_path.$class.'.php'))
            {
                require_once($app_path.$class.'.php');
                if ( ! class_exists($class, FALSE))
                {
                    throw new RuntimeException($app_path.$class.".php exists, but doesn't declare class ".$class);
                }

                log_message('info', config_item('subclass_prefix').'Model class loaded');
            }
        }

        $model = ucfirst($model);
        if ( ! class_exists($model, FALSE))
        {
            foreach ($this->_ci_model_paths as $mod_path)
            {
                if ( ! file_exists($mod_path.'models/'.$path.$model.'.php'))
                {
                    continue;
                }

                require_once($mod_path.'models/'.$path.$model.'.php');
                if ( ! class_exists($model, FALSE))
                {
                    throw new RuntimeException($mod_path."models/".$path.$model.".php exists, but doesn't declare class ".$model);
                }

                break;
            }

            if ( ! class_exists($model, FALSE))
            {
                throw new RuntimeException('Unable to locate the model you have specified: '.$model);
            }
        }

        if ( ! is_subclass_of($model, 'CI_Model'))
        {
            throw new RuntimeException("Class ".$model." doesn't extend CI_Model");
        }

        $this->_ci_models[] = $name;
        $model = new $model();
        $CI->$name = $model;
        log_message('info', 'Model "'.get_class($model).'" initialized');
        return $this;
    }

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

    /**
     * Database Loader
     *
     * @param    mixed    $params        Database configuration options
     * @param    bool    $return     Whether to return the database object
     * @param    bool    $query_builder    Whether to enable Query Builder
     *                    (overrides the configuration setting)
     *
     * @return    object|bool    Database object if $return is set to TRUE,
     *                    FALSE on failure, CI_Loader instance in any other case
     */
    public function database($params = '', $return = FALSE, $query_builder = NULL)
    {
        // Grab the super object
        $CI =& get_instance();

        // Do we even need to load the database class?
        if ($return === FALSE && $query_builder === NULL && isset($CI->db) && is_object($CI->db) && ! empty($CI->db->conn_id))
        {
            return FALSE;
        }

        require_once(BASEPATH.'database/DB.php');

        if ($return === TRUE)
        {
            return DB($params, $query_builder);
        }

        // Initialize the db variable. Needed to prevent
        // reference errors with some configurations
        $CI->db = '';

        // Load the DB class
        $CI->db =& DB($params, $query_builder);
        return $this;
    }

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

    /**
     * Load the Database Utilities Class
     *
     * @param    object    $db    Database object
     * @param    bool    $return    Whether to return the DB Utilities class object or not
     * @return    object
     */
    public function dbutil($db = NULL, $return = FALSE)
    {
        $CI =& get_instance();

        if ( ! is_object($db) OR ! ($db instanceof CI_DB))
        {
            class_exists('CI_DB', FALSE) OR $this->database();
            $db =& $CI->db;
        }

        require_once(BASEPATH.'database/DB_utility.php');
        require_once(BASEPATH.'database/drivers/'.$db->dbdriver.'/'.$db->dbdriver.'_utility.php');
        $class = 'CI_DB_'.$db->dbdriver.'_utility';

        if ($return === TRUE)
        {
            return new $class($db);
        }

        $CI->dbutil = new $class($db);
        return $this;
    }

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

    /**
     * Load the Database Forge Class
     *
     * @param    object    $db    Database object
     * @param    bool    $return    Whether to return the DB Forge class object or not
     * @return    object
     */
    public function dbforge($db = NULL, $return = FALSE)
    {
        $CI =& get_instance();
        if ( ! is_object($db) OR ! ($db instanceof CI_DB))
        {
            class_exists('CI_DB', FALSE) OR $this->database();
            $db =& $CI->db;
        }

        require_once(BASEPATH.'database/DB_forge.php');
        require_once(BASEPATH.'database/drivers/'.$db->dbdriver.'/'.$db->dbdriver.'_forge.php');

        if ( ! empty($db->subdriver))
        {
            $driver_path = BASEPATH.'database/drivers/'.$db->dbdriver.'/subdrivers/'.$db->dbdriver.'_'.$db->subdriver.'_forge.php';
            if (file_exists($driver_path))
            {
                require_once($driver_path);
                $class = 'CI_DB_'.$db->dbdriver.'_'.$db->subdriver.'_forge';
            }
        }
        else
        {
            $class = 'CI_DB_'.$db->dbdriver.'_forge';
        }

        if ($return === TRUE)
        {
            return new $class($db);
        }

        $CI->dbforge = new $class($db);
        return $this;
    }

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

    /**
     * View Loader
     *
     * Loads "view" files.
     *
     * @param    string    $view    View name
     * @param    array    $vars    An associative array of data
     *                to be extracted for use in the view
     * @param    bool    $return    Whether to return the view output
     *                or leave it to the Output class
     * @return    object|string
     */
    public function view($view, $vars = array(), $return = FALSE)
    {
        return $this->_ci_load(array('_ci_view' => $view, '_ci_vars' => $this->_ci_prepare_view_vars($vars), '_ci_return' => $return));
    }

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

    /**
     * Generic File Loader
     *
     * @param    string    $path    File path
     * @param    bool    $return    Whether to return the file output
     * @return    object|string
     */
    public function file($path, $return = FALSE)
    {
        return $this->_ci_load(array('_ci_path' => $path, '_ci_return' => $return));
    }

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

    /**
     * Set Variables
     *
     * Once variables are set they become available within
     * the controller class and its "view" files.
     *
     * @param    array|object|string    $vars
     *                    An associative array or object containing values
     *                    to be set, or a value's name if string
     * @param     string    $val    Value to set, only used if $vars is a string
     * @return    object
     */
    public function vars($vars, $val = '')
    {
        $vars = is_string($vars)
            ? array($vars => $val)
            : $this->_ci_prepare_view_vars($vars);

        foreach ($vars as $key => $val)
        {
            $this->_ci_cached_vars[$key] = $val;
        }

        return $this;
    }

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

    /**
     * Clear Cached Variables
     *
     * Clears the cached variables.
     *
     * @return    CI_Loader
     */
    public function clear_vars()
    {
        $this->_ci_cached_vars = array();
        return $this;
    }

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

    /**
     * Get Variable
     *
     * Check if a variable is set and retrieve it.
     *
     * @param    string    $key    Variable name
     * @return    mixed    The variable or NULL if not found
     */
    public function get_var($key)
    {
        return isset($this->_ci_cached_vars[$key]) ? $this->_ci_cached_vars[$key] : NULL;
    }

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

    /**
     * Get Variables
     *
     * Retrieves all loaded variables.
     *
     * @return    array
     */
    public function get_vars()
    {
        return $this->_ci_cached_vars;
    }

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

    /**
     * Helper Loader
     *
     * @param    string|string[]    $helpers    Helper name(s)
     * @return    object
     */
    public function helper($helpers = array())
    {
        is_array($helpers) OR $helpers = array($helpers);
        foreach ($helpers as &$helper)
        {
            $filename = basename($helper);
            $filepath = ($filename === $helper) ? '' : substr($helper, 0, strlen($helper) - strlen($filename));
            $filename = strtolower(preg_replace('#(_helper)?(\.php)?$#i', '', $filename)).'_helper';
            $helper   = $filepath.$filename;

            if (isset($this->_ci_helpers[$helper]))
            {
                continue;
            }

            // Is this a helper extension request?
            $ext_helper = config_item('subclass_prefix').$filename;
            $ext_loaded = FALSE;
            foreach ($this->_ci_helper_paths as $path)
            {
                if (file_exists($path.'helpers/'.$ext_helper.'.php'))
                {
                    include_once($path.'helpers/'.$ext_helper.'.php');
                    $ext_loaded = TRUE;
                }
            }

            // If we have loaded extensions - check if the base one is here
            if ($ext_loaded === TRUE)
            {
                $base_helper = BASEPATH.'helpers/'.$helper.'.php';
                if ( ! file_exists($base_helper))
                {
                    show_error('Unable to load the requested file: helpers/'.$helper.'.php');
                }

                include_once($base_helper);
                $this->_ci_helpers[$helper] = TRUE;
                log_message('info', 'Helper loaded: '.$helper);
                continue;
            }

            // No extensions found ... try loading regular helpers and/or overrides
            foreach ($this->_ci_helper_paths as $path)
            {
                if (file_exists($path.'helpers/'.$helper.'.php'))
                {
                    include_once($path.'helpers/'.$helper.'.php');

                    $this->_ci_helpers[$helper] = TRUE;
                    log_message('info', 'Helper loaded: '.$helper);
                    break;
                }
            }

            // unable to load the helper
            if ( ! isset($this->_ci_helpers[$helper]))
            {
                show_error('Unable to load the requested file: helpers/'.$helper.'.php');
            }
        }

        return $this;
    }

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

    /**
     * Load Helpers
     *
     * An alias for the helper() method in case the developer has
     * written the plural form of it.
     *
     * @uses    CI_Loader::helper()
     * @param    string|string[]    $helpers    Helper name(s)
     * @return    object
     */
    public function helpers($helpers = array())
    {
        return $this->helper($helpers);
    }

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

    /**
     * Language Loader
     *
     * Loads language files.
     *
     * @param    string|string[]    $files    List of language file names to load
     * @param    string        Language name
     * @return    object
     */
    public function language($files, $lang = '')
    {
        get_instance()->lang->load($files, $lang);
        return $this;
    }

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

    /**
     * Config Loader
     *
     * Loads a config file (an alias for CI_Config::load()).
     *
     * @uses    CI_Config::load()
     * @param    string    $file            Configuration file name
     * @param    bool    $use_sections        Whether configuration values should be loaded into their own section
     * @param    bool    $fail_gracefully    Whether to just return FALSE or display an error message
     * @return    bool    TRUE if the file was loaded correctly or FALSE on failure
     */
    public function config($file, $use_sections = FALSE, $fail_gracefully = FALSE)
    {
        return get_instance()->config->load($file, $use_sections, $fail_gracefully);
    }

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

    /**
     * Driver Loader
     *
     * Loads a driver library.
     *
     * @param    string|string[]    $library    Driver name(s)
     * @param    array        $params        Optional parameters to pass to the driver
     * @param    string        $object_name    An optional object name to assign to
     *
     * @return    object|bool    Object or FALSE on failure if $library is a string
     *                and $object_name is set. CI_Loader instance otherwise.
     */
    public function driver($library, $params = NULL, $object_name = NULL)
    {
        if (is_array($library))
        {
            foreach ($library as $key => $value)
            {
                if (is_int($key))
                {
                    $this->driver($value, $params);
                }
                else
                {
                    $this->driver($key, $params, $value);
                }
            }

            return $this;
        }
        elseif (empty($library))
        {
            return FALSE;
        }

        if ( ! class_exists('CI_Driver_Library', FALSE))
        {
            // We aren't instantiating an object here, just making the base class available
            require BASEPATH.'libraries/Driver.php';
        }

        // We can save the loader some time since Drivers will *always* be in a subfolder,
        // and typically identically named to the library
        if ( ! strpos($library, '/'))
        {
            $library = ucfirst($library).'/'.$library;
        }

        return $this->library($library, $params, $object_name);
    }

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

    /**
     * Add Package Path
     *
     * Prepends a parent path to the library, model, helper and config
     * path arrays.
     *
     * @see    CI_Loader::$_ci_library_paths
     * @see    CI_Loader::$_ci_model_paths
     * @see CI_Loader::$_ci_helper_paths
     * @see CI_Config::$_config_paths
     *
     * @param    string    $path        Path to add
     * @param     bool    $view_cascade    (default: TRUE)
     * @return    object
     */
    public function add_package_path($path, $view_cascade = TRUE)
    {
        $path = rtrim($path, '/').'/';

        array_unshift($this->_ci_library_paths, $path);
        array_unshift($this->_ci_model_paths, $path);
        array_unshift($this->_ci_helper_paths, $path);

        $this->_ci_view_paths = array($path.'views/' => $view_cascade) + $this->_ci_view_paths;

        // Add config file path
        $config =& $this->_ci_get_component('config');
        $config->_config_paths[] = $path;

        return $this;
    }

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

    /**
     * Get Package Paths
     *
     * Return a list of all package paths.
     *
     * @param    bool    $include_base    Whether to include BASEPATH (default: FALSE)
     * @return    array
     */
    public function get_package_paths($include_base = FALSE)
    {
        return ($include_base === TRUE) ? $this->_ci_library_paths : $this->_ci_model_paths;
    }

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

    /**
     * Remove Package Path
     *
     * Remove a path from the library, model, helper and/or config
     * path arrays if it exists. If no path is provided, the most recently
     * added path will be removed removed.
     *
     * @param    string    $path    Path to remove
     * @return    object
     */
    public function remove_package_path($path = '')
    {
        $config =& $this->_ci_get_component('config');

        if ($path === '')
        {
            array_shift($this->_ci_library_paths);
            array_shift($this->_ci_model_paths);
            array_shift($this->_ci_helper_paths);
            array_shift($this->_ci_view_paths);
            array_pop($config->_config_paths);
        }
        else
        {
            $path = rtrim($path, '/').'/';
            foreach (array('_ci_library_paths', '_ci_model_paths', '_ci_helper_paths') as $var)
            {
                if (($key = array_search($path, $this->{$var})) !== FALSE)
                {
                    unset($this->{$var}[$key]);
                }
            }

            if (isset($this->_ci_view_paths[$path.'views/']))
            {
                unset($this->_ci_view_paths[$path.'views/']);
            }

            if (($key = array_search($path, $config->_config_paths)) !== FALSE)
            {
                unset($config->_config_paths[$key]);
            }
        }

        // make sure the application default paths are still in the array
        $this->_ci_library_paths = array_unique(array_merge($this->_ci_library_paths, array(APPPATH, BASEPATH)));
        $this->_ci_helper_paths = array_unique(array_merge($this->_ci_helper_paths, array(APPPATH, BASEPATH)));
        $this->_ci_model_paths = array_unique(array_merge($this->_ci_model_paths, array(APPPATH)));
        $this->_ci_view_paths = array_merge($this->_ci_view_paths, array(APPPATH.'views/' => TRUE));
        $config->_config_paths = array_unique(array_merge($config->_config_paths, array(APPPATH)));

        return $this;
    }

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

    /**
     * Internal CI Data Loader
     *
     * Used to load views and files.
     *
     * Variables are prefixed with _ci_ to avoid symbol collision with
     * variables made available to view files.
     *
     * @used-by    CI_Loader::view()
     * @used-by    CI_Loader::file()
     * @param    array    $_ci_data    Data to load
     * @return    object
     */
    protected function _ci_load($_ci_data)
    {
        // Set the default data variables
        foreach (array('_ci_view', '_ci_vars', '_ci_path', '_ci_return') as $_ci_val)
        {
            $$_ci_val = isset($_ci_data[$_ci_val]) ? $_ci_data[$_ci_val] : FALSE;
        }

        $file_exists = FALSE;

        // Set the path to the requested file
        if (is_string($_ci_path) && $_ci_path !== '')
        {
            $_ci_x = explode('/', $_ci_path);
            $_ci_file = end($_ci_x);
        }
        else
        {
            $_ci_ext = pathinfo($_ci_view, PATHINFO_EXTENSION);
            $_ci_file = ($_ci_ext === '') ? $_ci_view.'.php' : $_ci_view;

            foreach ($this->_ci_view_paths as $_ci_view_file => $cascade)
            {
                if (file_exists($_ci_view_file.$_ci_file))
                {
                    $_ci_path = $_ci_view_file.$_ci_file;
                    $file_exists = TRUE;
                    break;
                }

                if ( ! $cascade)
                {
                    break;
                }
            }
        }

        if ( ! $file_exists && ! file_exists($_ci_path))
        {
            show_error('Unable to load the requested file: '.$_ci_file);
        }

        // This allows anything loaded using $this->load (views, files, etc.)
        // to become accessible from within the Controller and Model functions.
        $_ci_CI =& get_instance();
        foreach (get_object_vars($_ci_CI) as $_ci_key => $_ci_var)
        {
            if ( ! isset($this->$_ci_key))
            {
                $this->$_ci_key =& $_ci_CI->$_ci_key;
            }
        }

        /*
         * Extract and cache variables
         *
         * You can either set variables using the dedicated $this->load->vars()
         * function or via the second parameter of this function. We'll merge
         * the two types and cache them so that views that are embedded within
         * other views can have access to these variables.
         */
        empty($_ci_vars) OR $this->_ci_cached_vars = array_merge($this->_ci_cached_vars, $_ci_vars);
        extract($this->_ci_cached_vars);

        /**
         * Buffer the output
         *
         * We buffer the output for two reasons:
         * 1. Speed. You get a significant speed boost.
         * 2. So that the final rendered template can be post-processed by
         *    the output class. Why do we need post processing? For one thing,
         *    in order to show the elapsed page load time. Unless we can
         *    intercept the content right before it's sent to the browser and
         *    then stop the timer it won't be accurate.
         */
        ob_start();

        include($_ci_path); // include() vs include_once() allows for multiple views with the same name
        log_message('info', 'File loaded: '.$_ci_path);

        // Return the file data if requested
        if ($_ci_return === TRUE)
        {
            $buffer = ob_get_contents();
            @ob_end_clean();
            return $buffer;
        }

        /*
         * Flush the buffer... or buff the flusher?
         *
         * In order to permit views to be nested within
         * other views, we need to flush the content back out whenever
         * we are beyond the first level of output buffering so that
         * it can be seen and included properly by the first included
         * template and any subsequent ones. Oy!
         */
        if (ob_get_level() > $this->_ci_ob_level + 1)
        {
            ob_end_flush();
        }
        else
        {
            $_ci_CI->output->append_output(ob_get_contents());
            @ob_end_clean();
        }

        return $this;
    }

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

    /**
     * Internal CI Library Loader
     *
     * @used-by    CI_Loader::library()
     * @uses    CI_Loader::_ci_init_library()
     *
     * @param    string    $class        Class name to load
     * @param    mixed    $params        Optional parameters to pass to the class constructor
     * @param    string    $object_name    Optional object name to assign to
     * @return    void
     */
    protected function _ci_load_library($class, $params = NULL, $object_name = NULL)
    {
        // Get the class name, and while we're at it trim any slashes.
        // The directory path can be included as part of the class name,
        // but we don't want a leading slash
        $class = str_replace('.php', '', trim($class, '/'));

        // Was the path included with the class name?
        // We look for a slash to determine this
        if (($last_slash = strrpos($class, '/')) !== FALSE)
        {
            // Extract the path
            $subdir = substr($class, 0, ++$last_slash);

            // Get the filename from the path
            $class = substr($class, $last_slash);
        }
        else
        {
            $subdir = '';
        }

        $class = ucfirst($class);

        // Is this a stock library? There are a few special conditions if so ...
        if (file_exists(BASEPATH.'libraries/'.$subdir.$class.'.php'))
        {
            return $this->_ci_load_stock_library($class, $subdir, $params, $object_name);
        }

        // Safety: Was the class already loaded by a previous call?
        if (class_exists($class, FALSE))
        {
            $property = $object_name;
            if (empty($property))
            {
                $property = strtolower($class);
                isset($this->_ci_varmap[$property]) && $property = $this->_ci_varmap[$property];
            }

            $CI =& get_instance();
            if (isset($CI->$property))
            {
                log_message('debug', $class.' class already loaded. Second attempt ignored.');
                return;
            }

            return $this->_ci_init_library($class, '', $params, $object_name);
        }

        // Let's search for the requested library file and load it.
        foreach ($this->_ci_library_paths as $path)
        {
            // BASEPATH has already been checked for
            if ($path === BASEPATH)
            {
                continue;
            }

            $filepath = $path.'libraries/'.$subdir.$class.'.php';
            // Does the file exist? No? Bummer...
            if ( ! file_exists($filepath))
            {
                continue;
            }

            include_once($filepath);
            return $this->_ci_init_library($class, '', $params, $object_name);
        }

        // One last attempt. Maybe the library is in a subdirectory, but it wasn't specified?
        if ($subdir === '')
        {
            return $this->_ci_load_library($class.'/'.$class, $params, $object_name);
        }

        // If we got this far we were unable to find the requested class.
        log_message('error', 'Unable to load the requested class: '.$class);
        show_error('Unable to load the requested class: '.$class);
    }

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

    /**
     * Internal CI Stock Library Loader
     *
     * @used-by    CI_Loader::_ci_load_library()
     * @uses    CI_Loader::_ci_init_library()
     *
     * @param    string    $library_name    Library name to load
     * @param    string    $file_path    Path to the library filename, relative to libraries/
     * @param    mixed    $params        Optional parameters to pass to the class constructor
     * @param    string    $object_name    Optional object name to assign to
     * @return    void
     */
    protected function _ci_load_stock_library($library_name, $file_path, $params, $object_name)
    {
        $prefix = 'CI_';

        if (class_exists($prefix.$library_name, FALSE))
        {
            if (class_exists(config_item('subclass_prefix').$library_name, FALSE))
            {
                $prefix = config_item('subclass_prefix');
            }

            $property = $object_name;
            if (empty($property))
            {
                $property = strtolower($library_name);
                isset($this->_ci_varmap[$property]) && $property = $this->_ci_varmap[$property];
            }

            $CI =& get_instance();
            if ( ! isset($CI->$property))
            {
                return $this->_ci_init_library($library_name, $prefix, $params, $object_name);
            }

            log_message('debug', $library_name.' class already loaded. Second attempt ignored.');
            return;
        }

        $paths = $this->_ci_library_paths;
        array_pop($paths); // BASEPATH
        array_pop($paths); // APPPATH (needs to be the first path checked)
        array_unshift($paths, APPPATH);

        foreach ($paths as $path)
        {
            if (file_exists($path = $path.'libraries/'.$file_path.$library_name.'.php'))
            {
                // Override
                include_once($path);
                if (class_exists($prefix.$library_name, FALSE))
                {
                    return $this->_ci_init_library($library_name, $prefix, $params, $object_name);
                }

                log_message('debug', $path.' exists, but does not declare '.$prefix.$library_name);
            }
        }

        include_once(BASEPATH.'libraries/'.$file_path.$library_name.'.php');

        // Check for extensions
        $subclass = config_item('subclass_prefix').$library_name;
        foreach ($paths as $path)
        {
            if (file_exists($path = $path.'libraries/'.$file_path.$subclass.'.php'))
            {
                include_once($path);
                if (class_exists($subclass, FALSE))
                {
                    $prefix = config_item('subclass_prefix');
                    break;
                }

                log_message('debug', $path.' exists, but does not declare '.$subclass);
            }
        }

        return $this->_ci_init_library($library_name, $prefix, $params, $object_name);
    }

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

    /**
     * Internal CI Library Instantiator
     *
     * @used-by    CI_Loader::_ci_load_stock_library()
     * @used-by    CI_Loader::_ci_load_library()
     *
     * @param    string        $class        Class name
     * @param    string        $prefix        Class name prefix
     * @param    array|null|bool    $config        Optional configuration to pass to the class constructor:
     *                        FALSE to skip;
     *                        NULL to search in config paths;
     *                        array containing configuration data
     * @param    string        $object_name    Optional object name to assign to
     * @return    void
     */
    protected function _ci_init_library($class, $prefix, $config = FALSE, $object_name = NULL)
    {
        // Is there an associated config file for this class? Note: these should always be lowercase
        if ($config === NULL)
        {
            // Fetch the config paths containing any package paths
            $config_component = $this->_ci_get_component('config');

            if (is_array($config_component->_config_paths))
            {
                $found = FALSE;
                foreach ($config_component->_config_paths as $path)
                {
                    // We test for both uppercase and lowercase, for servers that
                    // are case-sensitive with regard to file names. Load global first,
                    // override with environment next
                    if (file_exists($path.'config/'.strtolower($class).'.php'))
                    {
                        include($path.'config/'.strtolower($class).'.php');
                        $found = TRUE;
                    }
                    elseif (file_exists($path.'config/'.ucfirst(strtolower($class)).'.php'))
                    {
                        include($path.'config/'.ucfirst(strtolower($class)).'.php');
                        $found = TRUE;
                    }

                    if (file_exists($path.'config/'.ENVIRONMENT.'/'.strtolower($class).'.php'))
                    {
                        include($path.'config/'.ENVIRONMENT.'/'.strtolower($class).'.php');
                        $found = TRUE;
                    }
                    elseif (file_exists($path.'config/'.ENVIRONMENT.'/'.ucfirst(strtolower($class)).'.php'))
                    {
                        include($path.'config/'.ENVIRONMENT.'/'.ucfirst(strtolower($class)).'.php');
                        $found = TRUE;
                    }

                    // Break on the first found configuration, thus package
                    // files are not overridden by default paths
                    if ($found === TRUE)
                    {
                        break;
                    }
                }
            }
        }

        $class_name = $prefix.$class;

        // Is the class name valid?
        if ( ! class_exists($class_name, FALSE))
        {
            log_message('error', 'Non-existent class: '.$class_name);
            show_error('Non-existent class: '.$class_name);
        }

        // Set the variable name we will assign the class to
        // Was a custom class name supplied? If so we'll use it
        if (empty($object_name))
        {
            $object_name = strtolower($class);
            if (isset($this->_ci_varmap[$object_name]))
            {
                $object_name = $this->_ci_varmap[$object_name];
            }
        }

        // Don't overwrite existing properties
        $CI =& get_instance();
        if (isset($CI->$object_name))
        {
            if ($CI->$object_name instanceof $class_name)
            {
                log_message('debug', $class_name." has already been instantiated as '".$object_name."'. Second attempt aborted.");
                return;
            }

            show_error("Resource '".$object_name."' already exists and is not a ".$class_name." instance.");
        }

        // Save the class name and object name
        $this->_ci_classes[$object_name] = $class;

        // Instantiate the class
        $CI->$object_name = isset($config)
            ? new $class_name($config)
            : new $class_name();
    }

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

    /**
     * CI Autoloader
     *
     * Loads component listed in the config/autoload.php file.
     *
     * @used-by    CI_Loader::initialize()
     * @return    void
     */
    protected function _ci_autoloader()
    {
        if (file_exists(APPPATH.'config/autoload.php'))
        {
            include(APPPATH.'config/autoload.php');
        }

        if (file_exists(APPPATH.'config/'.ENVIRONMENT.'/autoload.php'))
        {
            include(APPPATH.'config/'.ENVIRONMENT.'/autoload.php');
        }

        if ( ! isset($autoload))
        {
            return;
        }

        // Autoload packages
        if (isset($autoload['packages']))
        {
            foreach ($autoload['packages'] as $package_path)
            {
                $this->add_package_path($package_path);
            }
        }

        // Load any custom config file
        if (count($autoload['config']) > 0)
        {
            foreach ($autoload['config'] as $val)
            {
                $this->config($val);
            }
        }

        // Autoload helpers and languages
        foreach (array('helper', 'language') as $type)
        {
            if (isset($autoload[$type]) && count($autoload[$type]) > 0)
            {
                $this->$type($autoload[$type]);
            }
        }

        // Autoload drivers
        if (isset($autoload['drivers']))
        {
            $this->driver($autoload['drivers']);
        }

        // Load libraries
        if (isset($autoload['libraries']) && count($autoload['libraries']) > 0)
        {
            // Load the database driver.
            if (in_array('database', $autoload['libraries']))
            {
                $this->database();
                $autoload['libraries'] = array_diff($autoload['libraries'], array('database'));
            }

            // Load all other libraries
            $this->library($autoload['libraries']);
        }

        // Autoload models
        if (isset($autoload['model']))
        {
            $this->model($autoload['model']);
        }
    }

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

    /**
     * Prepare variables for _ci_vars, to be later extract()-ed inside views
     *
     * Converts objects to associative arrays and filters-out internal
     * variable names (i.e. keys prefixed with '_ci_').
     *
     * @param    mixed    $vars
     * @return    array
     */
    protected function _ci_prepare_view_vars($vars)
    {
        if ( ! is_array($vars))
        {
            $vars = is_object($vars)
                ? get_object_vars($vars)
                : array();
        }

        foreach (array_keys($vars) as $key)
        {
            if (strncmp($key, '_ci_', 4) === 0)
            {
                unset($vars[$key]);
            }
        }

        return $vars;
    }

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

    /**
     * CI Component getter
     *
     * Get a reference to a specific library or model.
     *
     * @param     string    $component    Component name
     * @return    bool
     */
    protected function &_ci_get_component($component)
    {
        $CI =& get_instance();
        return $CI->$component;
    }
}