google_forms/system/core/Output.php

<?php

/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2019 - 2022, CodeIgniter Foundation
 *
 * 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/)
 * @copyright   Copyright (c) 2019 - 2022, CodeIgniter Foundation (https://codeigniter.com/)
 * @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');

/**
 * Output Class
 *
 * Responsible for sending final output to the browser.
 *
 * @package     CodeIgniter
 * @subpackage  Libraries
 * @category    Output
 * @author      EllisLab Dev Team
 * @link        https://codeigniter.com/userguide3/libraries/output.html
 */
class CI_Output
{
    /**
     * Final output string
     *
     * @var string
     */
    public $final_output = '';

    /**
     * Cache expiration time
     *
     * @var int
     */
    public $cache_expiration = 0;

    /**
     * List of server headers
     *
     * @var array
     */
    public $headers = array();

    /**
     * List of mime types
     *
     * @var array
     */
    public $mimes = array();

    /**
     * Mime-type for the current page
     *
     * @var string
     */
    protected $mime_type = 'text/html';

    /**
     * Enable Profiler flag
     *
     * @var bool
     */
    public $enable_profiler = false;

    /**
     * php.ini zlib.output_compression flag
     *
     * @var bool
     */
    protected $_zlib_oc = false;

    /**
     * CI output compression flag
     *
     * @var bool
     */
    protected $_compress_output = false;

    /**
     * List of profiler sections
     *
     * @var array
     */
    protected $_profiler_sections = array();

    /**
     * Parse markers flag
     *
     * Whether or not to parse variables like {elapsed_time} and {memory_usage}.
     *
     * @var bool
     */
    public $parse_exec_vars = true;

    /**
     * mbstring.func_overload flag
     *
     * @var bool
     */
    protected static $func_overload;

    /**
     * Class constructor
     *
     * Determines whether zLib output compression will be used.
     *
     * @return  void
     */
    public function __construct()
    {
        $this->_zlib_oc = (bool) ini_get('zlib.output_compression');
        $this->_compress_output = (
            $this->_zlib_oc === false
            && config_item('compress_output') === true
            && extension_loaded('zlib')
        );

        isset(self::$func_overload) or self::$func_overload = (! is_php('8.0') && extension_loaded('mbstring') && @ini_get('mbstring.func_overload'));

        // Get mime types for later
        $this->mimes = & get_mimes();

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

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

    /**
     * Get Output
     *
     * Returns the current output string.
     *
     * @return  string
     */
    public function get_output()
    {
        return $this->final_output;
    }

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

    /**
     * Set Output
     *
     * Sets the output string.
     *
     * @param   string  $output Output data
     * @return  CI_Output
     */
    public function set_output($output)
    {
        $this->final_output = $output;
        return $this;
    }

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

    /**
     * Append Output
     *
     * Appends data onto the output string.
     *
     * @param   string  $output Data to append
     * @return  CI_Output
     */
    public function append_output($output)
    {
        $this->final_output .= $output;
        return $this;
    }

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

    /**
     * Set Header
     *
     * Lets you set a server header which will be sent with the final output.
     *
     * Note: If a file is cached, headers will not be sent.
     * @todo    We need to figure out how to permit headers to be cached.
     *
     * @param   string  $header     Header
     * @param   bool    $replace    Whether to replace the old header value, if already set
     * @return  CI_Output
     */
    public function set_header($header, $replace = true)
    {
        // If zlib.output_compression is enabled it will compress the output,
        // but it will not modify the content-length header to compensate for
        // the reduction, causing the browser to hang waiting for more data.
        // We'll just skip content-length in those cases.
        if ($this->_zlib_oc && strncasecmp($header, 'content-length', 14) === 0) {
            return $this;
        }

        $this->headers[] = array($header, $replace);
        return $this;
    }

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

    /**
     * Set Content-Type Header
     *
     * @param   string  $mime_type  Extension of the file we're outputting
     * @param   string  $charset    Character set (default: NULL)
     * @return  CI_Output
     */
    public function set_content_type($mime_type, $charset = null)
    {
        if (strpos($mime_type, '/') === false) {
            $extension = ltrim($mime_type, '.');

            // Is this extension supported?
            if (isset($this->mimes[$extension])) {
                $mime_type = & $this->mimes[$extension];

                if (is_array($mime_type)) {
                    $mime_type = current($mime_type);
                }
            }
        }

        $this->mime_type = $mime_type;

        if (empty($charset)) {
            $charset = config_item('charset');
        }

        $header = 'Content-Type: ' . $mime_type
            . (empty($charset) ? '' : '; charset=' . $charset);

        $this->headers[] = array($header, true);
        return $this;
    }

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

    /**
     * Get Current Content-Type Header
     *
     * @return  string  'text/html', if not already set
     */
    public function get_content_type()
    {
        for ($i = 0, $c = count($this->headers); $i < $c; $i++) {
            if (sscanf($this->headers[$i][0], 'Content-Type: %[^;]', $content_type) === 1) {
                return $content_type;
            }
        }

        return 'text/html';
    }

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

    /**
     * Get Header
     *
     * @param   string  $header
     * @return  string
     */
    public function get_header($header)
    {
        // We only need [x][0] from our multi-dimensional array
        $header_lines = array_map(function ($headers) {
            return array_shift($headers);
        }, $this->headers);

        $headers = array_merge(
            $header_lines,
            headers_list()
        );

        if (empty($headers) or empty($header)) {
            return null;
        }

        // Count backwards, in order to get the last matching header
        for ($c = count($headers) - 1; $c > -1; $c--) {
            if (strncasecmp($header, $headers[$c], $l = self::strlen($header)) === 0) {
                return trim(self::substr($headers[$c], $l + 1));
            }
        }

        return null;
    }

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

    /**
     * Set HTTP Status Header
     *
     * As of version 1.7.2, this is an alias for common function
     * set_status_header().
     *
     * @param   int $code   Status code (default: 200)
     * @param   string  $text   Optional message
     * @return  CI_Output
     */
    public function set_status_header($code = 200, $text = '')
    {
        set_status_header($code, $text);
        return $this;
    }

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

    /**
     * Enable/disable Profiler
     *
     * @param   bool    $val    TRUE to enable or FALSE to disable
     * @return  CI_Output
     */
    public function enable_profiler($val = true)
    {
        $this->enable_profiler = is_bool($val) ? $val : true;
        return $this;
    }

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

    /**
     * Set Profiler Sections
     *
     * Allows override of default/config settings for
     * Profiler section display.
     *
     * @param   array   $sections   Profiler sections
     * @return  CI_Output
     */
    public function set_profiler_sections($sections)
    {
        if (isset($sections['query_toggle_count'])) {
            $this->_profiler_sections['query_toggle_count'] = (int) $sections['query_toggle_count'];
            unset($sections['query_toggle_count']);
        }

        foreach ($sections as $section => $enable) {
            $this->_profiler_sections[$section] = ($enable !== false);
        }

        return $this;
    }

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

    /**
     * Set Cache
     *
     * @param   int $time   Cache expiration time in minutes
     * @return  CI_Output
     */
    public function cache($time)
    {
        $this->cache_expiration = is_numeric($time) ? $time : 0;
        return $this;
    }

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

    /**
     * Display Output
     *
     * Processes and sends finalized output data to the browser along
     * with any server headers and profile data. It also stops benchmark
     * timers so the page rendering speed and memory usage can be shown.
     *
     * Note: All "view" data is automatically put into $this->final_output
     *   by controller class.
     *
     * @uses    CI_Output::$final_output
     * @param   string  $output Output data override
     * @return  void
     */
    public function _display($output = '')
    {
        // Note:  We use load_class() because we can't use $CI =& get_instance()
        // since this function is sometimes called by the caching mechanism,
        // which happens before the CI super object is available.
        $BM = & load_class('Benchmark', 'core');
        $CFG = & load_class('Config', 'core');

        // Grab the super object if we can.
        if (class_exists('CI_Controller', false)) {
            $CI = & get_instance();
        }

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

        // Set the output data
        if ($output === '') {
            $output = & $this->final_output;
        }

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

        // Do we need to write a cache file? Only if the controller does not have its
        // own _output() method and we are not dealing with a cache file, which we
        // can determine by the existence of the $CI object above
        if ($this->cache_expiration > 0 && isset($CI) && ! method_exists($CI, '_output')) {
            $this->_write_cache($output);
        }

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

        // Parse out the elapsed time and memory usage,
        // then swap the pseudo-variables with the data

        $elapsed = $BM->elapsed_time('total_execution_time_start', 'total_execution_time_end');

        if ($this->parse_exec_vars === true) {
            $memory = round(memory_get_usage() / 1024 / 1024, 2) . 'MB';
            $output = str_replace(array('{elapsed_time}', '{memory_usage}'), array($elapsed, $memory), $output);
        }

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

        // Is compression requested?
        if (
            isset($CI) // This means that we're not serving a cache file, if we were, it would already be compressed
            && $this->_compress_output === true
            && isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== false
        ) {
            ob_start('ob_gzhandler');
        }

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

        // Are there any server headers to send?
        if (count($this->headers) > 0) {
            foreach ($this->headers as $header) {
                @header($header[0], $header[1]);
            }
        }

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

        // Does the $CI object exist?
        // If not we know we are dealing with a cache file so we'll
        // simply echo out the data and exit.
        if (! isset($CI)) {
            if ($this->_compress_output === true) {
                if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== false) {
                    header('Content-Encoding: gzip');
                    header('Content-Length: ' . self::strlen($output));
                } else {
                    // User agent doesn't support gzip compression,
                    // so we'll have to decompress our cache
                    $output = gzinflate(self::substr($output, 10, -8));
                }
            }

            echo $output;
            log_message('info', 'Final output sent to browser');
            log_message('debug', 'Total execution time: ' . $elapsed);
            return;
        }

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

        // Do we need to generate profile data?
        // If so, load the Profile class and run it.
        if ($this->enable_profiler === true) {
            $CI->load->library('profiler');
            if (! empty($this->_profiler_sections)) {
                $CI->profiler->set_sections($this->_profiler_sections);
            }

            // If the output data contains closing </body> and </html> tags
            // we will remove them and add them back after we insert the profile data
            $output = preg_replace('|</body>.*?</html>|is', '', $output, -1, $count) . $CI->profiler->run();
            if ($count > 0) {
                $output .= '</body></html>';
            }
        }

        // Does the controller contain a function named _output()?
        // If so send the output there.  Otherwise, echo it.
        if (method_exists($CI, '_output')) {
            $CI->_output($output);
        } else {
            echo $output; // Send it to the browser!
        }

        log_message('info', 'Final output sent to browser');
        log_message('debug', 'Total execution time: ' . $elapsed);
    }

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

    /**
     * Write Cache
     *
     * @param   string  $output Output data to cache
     * @return  void
     */
    public function _write_cache($output)
    {
        $CI = & get_instance();
        $path = $CI->config->item('cache_path');
        $cache_path = ($path === '') ? APPPATH . 'cache/' : $path;

        if (! is_dir($cache_path) or ! is_really_writable($cache_path)) {
            log_message('error', 'Unable to write cache file: ' . $cache_path);
            return;
        }

        $uri = $CI->config->item('base_url')
            . $CI->config->item('index_page')
            . $CI->uri->uri_string();

        if (($cache_query_string = $CI->config->item('cache_query_string')) && ! empty($_SERVER['QUERY_STRING'])) {
            if (is_array($cache_query_string)) {
                $uri .= '?' . http_build_query(array_intersect_key($_GET, array_flip($cache_query_string)));
            } else {
                $uri .= '?' . $_SERVER['QUERY_STRING'];
            }
        }

        $cache_path .= md5($uri);

        if (! $fp = @fopen($cache_path, 'w+b')) {
            log_message('error', 'Unable to write cache file: ' . $cache_path);
            return;
        }

        if (! flock($fp, LOCK_EX)) {
            log_message('error', 'Unable to secure a file lock for file at: ' . $cache_path);
            fclose($fp);
            return;
        }

        // If output compression is enabled, compress the cache
        // itself, so that we don't have to do that each time
        // we're serving it
        if ($this->_compress_output === true) {
            $output = gzencode($output);

            if ($this->get_header('content-type') === null) {
                $this->set_content_type($this->mime_type);
            }
        }

        $expire = time() + ($this->cache_expiration * 60);

        // Put together our serialized info.
        $cache_info = serialize(array(
            'expire'    => $expire,
            'headers'   => $this->headers
        ));

        $output = $cache_info . 'ENDCI--->' . $output;

        for ($written = 0, $length = self::strlen($output); $written < $length; $written += $result) {
            if (($result = fwrite($fp, self::substr($output, $written))) === false) {
                break;
            }
        }

        flock($fp, LOCK_UN);
        fclose($fp);

        if (! is_int($result)) {
            @unlink($cache_path);
            log_message('error', 'Unable to write the complete cache content at: ' . $cache_path);
            return;
        }

        chmod($cache_path, 0640);
        log_message('debug', 'Cache file written: ' . $cache_path);

        // Send HTTP cache-control headers to browser to match file cache settings.
        $this->set_cache_header($_SERVER['REQUEST_TIME'], $expire);
    }

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

    /**
     * Update/serve cached output
     *
     * @uses    CI_Config
     * @uses    CI_URI
     *
     * @param   object  &$CFG   CI_Config class instance
     * @param   object  &$URI   CI_URI class instance
     * @return  bool    TRUE on success or FALSE on failure
     */
    public function _display_cache(&$CFG, &$URI)
    {
        $cache_path = ($CFG->item('cache_path') === '') ? APPPATH . 'cache/' : $CFG->item('cache_path');

        // Build the file path. The file name is an MD5 hash of the full URI
        $uri = $CFG->item('base_url') . $CFG->item('index_page') . $URI->uri_string;

        if (($cache_query_string = $CFG->item('cache_query_string')) && ! empty($_SERVER['QUERY_STRING'])) {
            if (is_array($cache_query_string)) {
                $uri .= '?' . http_build_query(array_intersect_key($_GET, array_flip($cache_query_string)));
            } else {
                $uri .= '?' . $_SERVER['QUERY_STRING'];
            }
        }

        $filepath = $cache_path . md5($uri);

        if (! file_exists($filepath) or ! $fp = @fopen($filepath, 'rb')) {
            return false;
        }

        flock($fp, LOCK_SH);

        $cache = (filesize($filepath) > 0) ? fread($fp, filesize($filepath)) : '';

        flock($fp, LOCK_UN);
        fclose($fp);

        // Look for embedded serialized file info.
        if (! preg_match('/^(.*)ENDCI--->/', $cache, $match)) {
            return false;
        }

        $cache_info = unserialize($match[1]);
        $expire = $cache_info['expire'];

        $last_modified = filemtime($filepath);

        // Has the file expired?
        if ($_SERVER['REQUEST_TIME'] >= $expire && is_really_writable($cache_path)) {
            // If so we'll delete it.
            @unlink($filepath);
            log_message('debug', 'Cache file has expired. File deleted.');
            return false;
        }

        // Send the HTTP cache control headers
        $this->set_cache_header($last_modified, $expire);

        // Add headers from cache file.
        foreach ($cache_info['headers'] as $header) {
            $this->set_header($header[0], $header[1]);
        }

        // Display the cache
        $this->_display(self::substr($cache, self::strlen($match[0])));
        log_message('debug', 'Cache file is current. Sending it to browser.');
        return true;
    }

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

    /**
     * Delete cache
     *
     * @param   string  $uri    URI string
     * @return  bool
     */
    public function delete_cache($uri = '')
    {
        $CI = & get_instance();
        $cache_path = $CI->config->item('cache_path');
        if ($cache_path === '') {
            $cache_path = APPPATH . 'cache/';
        }

        if (! is_dir($cache_path)) {
            log_message('error', 'Unable to find cache path: ' . $cache_path);
            return false;
        }

        if (empty($uri)) {
            $uri = $CI->uri->uri_string();

            if (($cache_query_string = $CI->config->item('cache_query_string')) && ! empty($_SERVER['QUERY_STRING'])) {
                if (is_array($cache_query_string)) {
                    $uri .= '?' . http_build_query(array_intersect_key($_GET, array_flip($cache_query_string)));
                } else {
                    $uri .= '?' . $_SERVER['QUERY_STRING'];
                }
            }
        }

        $cache_path .= md5($CI->config->item('base_url') . $CI->config->item('index_page') . ltrim($uri, '/'));

        if (! @unlink($cache_path)) {
            log_message('error', 'Unable to delete cache file for ' . $uri);
            return false;
        }

        return true;
    }

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

    /**
     * Set Cache Header
     *
     * Set the HTTP headers to match the server-side file cache settings
     * in order to reduce bandwidth.
     *
     * @param   int $last_modified  Timestamp of when the page was last modified
     * @param   int $expiration Timestamp of when should the requested page expire from cache
     * @return  void
     */
    public function set_cache_header($last_modified, $expiration)
    {
        $max_age = $expiration - $_SERVER['REQUEST_TIME'];

        if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && $last_modified <= strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
            $this->set_status_header(304);
            exit;
        }

        header('Pragma: public');
        header('Cache-Control: max-age=' . $max_age . ', public');
        header('Expires: ' . gmdate('D, d M Y H:i:s', $expiration) . ' GMT');
        header('Last-modified: ' . gmdate('D, d M Y H:i:s', $last_modified) . ' GMT');
    }

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

    /**
     * Byte-safe strlen()
     *
     * @param   string  $str
     * @return  int
     */
    protected static function strlen($str)
    {
        return (self::$func_overload)
            ? mb_strlen($str, '8bit')
            : strlen($str);
    }

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

    /**
     * Byte-safe substr()
     *
     * @param   string  $str
     * @param   int $start
     * @param   int $length
     * @return  string
     */
    protected static function substr($str, $start, $length = null)
    {
        if (self::$func_overload) {
            // mb_substr($str, $start, null, '8bit') returns an empty
            // string on PHP 5.3
            isset($length) or $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
            return mb_substr($str, $start, $length, '8bit');
        }

        return isset($length)
            ? substr($str, $start, $length)
            : substr($str, $start);
    }
}