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output.html
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<!DOCTYPE html>
<!--[if lt IE 7]> <html class="no-js lt-ie9 lt-ie8 lt-ie7"> <![endif]-->
<!--[if IE 7]> <html class="no-js lt-ie9 lt-ie8"> <![endif]-->
<!--[if IE 8]> <html class="no-js lt-ie9"> <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js"> <!--<![endif]-->
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<title></title>
<meta name="description" content="">
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- Place favicon.ico and apple-touch-icon.png in the root directory -->
<link rel="stylesheet" href="css/normalize.css">
<link rel="stylesheet" href="css/main.css">
<script src="js/vendor/modernizr-2.6.2.min.js"></script>
<link rel="stylesheet" href="css/bootstrap.css">
<link rel="stylesheet" href="css/shCore.css">
<link rel="stylesheet" href="css/shThemeDefault.css">
<script src="js/shCore.js"></script>
<script src="js/shBrushPhp.js"></script>
</head>
<body>
<!--[if lt IE 7]>
<p class="browsehappy">You are using an <strong>outdated</strong> browser. Please <a href="http://browsehappy.com/">upgrade your browser</a> to improve your experience.</p>
<![endif]-->
<!-- Add your site or application content here -->
<div class='alert alert-success'>
我們開始分析core/Output.php。<br/>
它負責產出最後結果，並傳送給使用者（瀏覽器）。
</div>
<!-- You also need to add some content to highlight, but that is covered elsewhere. -->
<pre class="brush: php">
<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
/**
* CodeIgniter
*
* An open source application development framework for PHP 5.1.6 or newer
*
* @package CodeIgniter
* @author ExpressionEngine Dev Team
* @copyright Copyright (c) 2008 - 2011, EllisLab, Inc.
* @license http://codeigniter.com/user_guide/license.html
* @link http://codeigniter.com
* @since Version 1.0
* @filesource
*/
// ------------------------------------------------------------------------
/**
* Output Class
*
* Responsible for sending final output to browser
*
* @package CodeIgniter
* @subpackage Libraries
* @category Output
* @author ExpressionEngine Dev Team
* @link http://codeigniter.com/user_guide/libraries/output.html
*/
class CI_Output {
/**
* Current output string
*
* @var string
* @access protected
*/
protected $final_output;
/**
* Cache expiration time
*
* @var int
* @access protected
*/
protected $cache_expiration = 0;
/**
* List of server headers
*
* @var array
* @access protected
*/
protected $headers = array();
/**
* List of mime types
*
* @var array
* @access protected
*/
protected $mime_types = array();
/**
* Determines wether profiler is enabled
*
* @var book
* @access protected
*/
protected $enable_profiler = FALSE;
/**
* Determines if output compression is enabled
*
* @var bool
* @access protected
*/
protected $_zlib_oc = FALSE;
/**
* List of profiler sections
*
* @var array
* @access protected
*/
protected $_profiler_sections = array();
/**
* Whether or not to parse variables like {elapsed_time} and {memory_usage}
*
* @var bool
* @access protected
*/
protected $parse_exec_vars = TRUE;
/**
* Constructor
*
*/
function __construct()
{
$this->_zlib_oc = @ini_get('zlib.output_compression');
// Get mime types for later
if (defined('ENVIRONMENT') AND file_exists(APPPATH.'config/'.ENVIRONMENT.'/mimes.php'))
{
include APPPATH.'config/'.ENVIRONMENT.'/mimes.php';
}
else
{
include APPPATH.'config/mimes.php';
}
$this->mime_types = $mimes;
log_message('debug', "Output Class Initialized");
}
// --------------------------------------------------------------------
/**
* Get Output
*
* Returns the current output string
*
* @access public
* @return string
*/
function get_output()
{
return $this->final_output;
}
// --------------------------------------------------------------------
/**
* Set Output
*
* Sets the output string
*
* @access public
* @param string
* @return void
*/
function set_output($output)
{
$this->final_output = $output;
return $this;
}
</pre>
<div class='alert alert-success'>
這個set函數最後傳回 $this，這讓函數能夠串接起來使用。<br/>
在不需要回傳值的函數，常常可以這麼做。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Append Output
*
* Appends data onto the output string
*
* @access public
* @param string
* @return void
*/
function append_output($output)
{
if ($this->final_output == '')
{
$this->final_output = $output;
}
else
{
$this->final_output .= $output;
}
return $this;
}
</pre>
<div class='alert alert-danger'>
注意這個將字串加進output的函數。<br/>
我認為if判斷式多餘了，直接 $this->final_output .= $output 即可。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Set Header
*
* Lets you set a server header which will be outputted with the final display.
*
* Note: If a file is cached, headers will not be sent. We need to figure out
* how to permit header data to be saved with the cache data...
*
* @access public
* @param string
* @param bool
* @return void
*/
function set_header($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;
}
$this->headers[] = array($header, $replace);
return $this;
}
</pre>
<div class='alert alert-success'>
本來我只知道，PHP的字串比較，用strcmp比==好。<br />
看到這邊才知道，還有strncasecmp跟strncmp函數。
</div>
<div class='alert alert-danger'>
$header是字串、$replace是布林值，這邊卻將他們放進一個陣列，然後再塞進headers變數。<br/>
我個人很討厭這種將不同類型變數放進同一個陣列的作法：這代表讀這段code的人要先知道陣列內的順序有特殊意義、而不只是順序，否則將難以理解。<br/>
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Set Content Type Header
*
* @access public
* @param string extension of the file we're outputting
* @return void
*/
function set_content_type($mime_type)
{
if (strpos($mime_type, '/') === FALSE)
{
$extension = ltrim($mime_type, '.');
// Is this extension supported?
if (isset($this->mime_types[$extension]))
{
$mime_type =& $this->mime_types[$extension];
if (is_array($mime_type))
{
$mime_type = current($mime_type);
}
}
}
$header = 'Content-Type: '.$mime_type;
$this->headers[] = array($header, TRUE);
return $this;
}
// --------------------------------------------------------------------
/**
* Set HTTP Status Header
* moved to Common procedural functions in 1.7.2
*
* @access public
* @param int the status code
* @param string
* @return void
*/
function set_status_header($code = 200, $text = '')
{
set_status_header($code, $text);
return $this;
}
</pre>
<div class='alert alert-success'>
這邊看得到為了維持與舊版的相容性所留下的痕跡。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Enable/disable Profiler
*
* @access public
* @param bool
* @return void
*/
function enable_profiler($val = TRUE)
{
$this->enable_profiler = (is_bool($val)) ? $val : TRUE;
return $this;
}
</pre>
<div class='alert alert-success'>
一個漂亮的防禦性編程。不是布林值的一律視為TRUE。只用了一行。<br/>
不期待回傳值的函數看來全都寫成了回傳 $this。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Set Profiler Sections
*
* Allows override of default / config settings for Profiler section display
*
* @access public
* @param array
* @return void
*/
function set_profiler_sections($sections)
{
foreach ($sections as $section => $enable)
{
$this->_profiler_sections[$section] = ($enable !== FALSE) ? TRUE : FALSE;
}
return $this;
}
// --------------------------------------------------------------------
/**
* Set Cache
*
* @access public
* @param integer
* @return void
*/
function cache($time)
{
$this->cache_expiration = ( ! is_numeric($time)) ? 0 : $time;
return $this;
}
// --------------------------------------------------------------------
/**
* Display Output
*
* All "view" data is automatically put into this variable by the controller class:
*
* $this->final_output
*
* This function sends the finalized output data to the browser along
* with any server headers and profile data. It also stops the
* benchmark timer so the page rendering speed and memory usage can be shown.
*
* @access public
* @param string
* @return mixed
*/
function _display($output = '')
{
// Note: We use globals 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.
global $BM, $CFG;
// Grab the super object if we can.
if (class_exists('CI_Controller'))
{
$CI =& get_instance();
}
// --------------------------------------------------------------------
// Set the output data
if ($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);
}
</pre>
<div class='alert alert-success'>
若是要求CI在controller內cache頁面，會使用<br/>
$this->output->cache(1); //tells the CI to cache this page for 1 minute<br/>
設定快取時間。所以若是cache_expiration大於零，表示有被要求快取此頁面。
</div>
<div class='alert alert-success'>
controller若是有定義_output函數，則Output類別不會將結果直接echo到瀏覽器，而是丟給_output去處理。<br/>
那樣的話，此處不做cache，因為不知道controller拿到資料會接著做什麼修改。<br/>
</div>
<div class='alert alert-danger'>
此_display函數有時是被快取機制所呼叫。那樣的話，便不需要寫入cache。<br/>
至於如何得知是被快取機制呼叫？是利用isset($CI)判定全域變數的存在。<br/>
我認為這很醜、光看isset($CI)也看不出是在判斷什麼東西。code可讀性很差。<br/>我認為這是濫用全域變數的一個例子。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
// 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 = ( ! function_exists('memory_get_usage')) ? '0' : round(memory_get_usage()/1024/1024, 2).'MB';
$output = str_replace('{elapsed_time}', $elapsed, $output);
$output = str_replace('{memory_usage}', $memory, $output);
}
// --------------------------------------------------------------------
// Is compression requested?
if ($CFG->item('compress_output') === TRUE && $this->_zlib_oc == FALSE)
{
if (extension_loaded('zlib'))
{
if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) AND 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))
{
echo $output;
log_message('debug', "Final output sent to browser");
log_message('debug', "Total execution time: ".$elapsed);
return TRUE;
}
// --------------------------------------------------------------------
// 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
if (preg_match("|</body>.*?</html>|is", $output))
{
$output = preg_replace("|</body>.*?</html>|is", '', $output);
$output .= $CI->profiler->run();
$output .= '</body></html>';
}
else
{
$output .= $CI->profiler->run();
}
}
// --------------------------------------------------------------------
// Does the controller contain a function named _output()?
// If so send the output there. Otherwise, echo it.
if (method_exists($CI, '_output'))
{
$CI->_output($output);
}
else
{
echo $output; // Send it to the browser!
}
log_message('debug', "Final output sent to browser");
log_message('debug', "Total execution time: ".$elapsed);
}
</pre>
<div class='alert alert-success'>
整個Output類別的重點，將結果echo給瀏覽器。
</div>
<div class='alert alert-danger'>
有一個用來計算整個CI執行時間的benchmark物件在這裡出現，並計算出整個執行時間。<br/>
_display根據名稱應該只負責展示最後結果給瀏覽器，卻多了計算執行時間的動作。<br />
我認為這違反了<a href='http://zh.wikipedia.org/wiki/%E5%8D%95%E4%B8%80%E5%8A%9F%E8%83%BD%E5%8E%9F%E5%88%99'>single responsibility principle</a>，增加了維護與理解的難度。<br />
不只是函數名稱，整個類別就叫做Output，不應該做展示以外的動作。<br/>
硬是為了支援benchmark功能，而將程式碼寫在這裡，我認為是quick and dirty solution。
</div>
<div class='alert alert-danger'>
除此之外，最開始處看到了它需要兩個全域變數$BM與$CFG的支援，並且接著對CI_Controller類別與get_instance全域函數有相依性。<br />
事實上，既然都寫成了類別，類別運作所需要的資料應該可以由建構式傳入、或是撰寫某些set函數設定。<br />
這邊寫成這樣，我認為是設計缺陷的一種、不夠Object-Oriented Design。<br />
看完整個函數，會發現它負責的事情滿雜的、不好理解。這通常暗示了code smell（程式碼臭掉了）。
</div>
<pre class="brush: php">
// --------------------------------------------------------------------
/**
* Write a Cache File
*
* @access public
* @param string
* @return void
*/
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;
}
</pre>
<div class='alert alert-success'>
檢查cache路徑是否存在、是否能夠寫入。<br/>
若是不行，則以log紀錄，並且直接return。<br/>
</div>
<pre class="brush: php">
$uri = $CI->config->item('base_url').
$CI->config->item('index_page').
$CI->uri->uri_string();
$cache_path .= md5($uri);
if ( ! $fp = @fopen($cache_path, FOPEN_WRITE_CREATE_DESTRUCTIVE))
{
log_message('error', "Unable to write cache file: ".$cache_path);
return;
}
</pre>
<div class='alert alert-success'>
FOPEN_WRITE_CREATE_DESTRUCTIVE只是constants.php裡面的一個自訂常數，不要緊張。
</div>
<pre class="brush: php">
$expire = time() + ($this->cache_expiration * 60);
if (flock($fp, LOCK_EX))
{
fwrite($fp, $expire.'TS--->'.$output);
flock($fp, LOCK_UN);
}
else
{
log_message('error', "Unable to secure a file lock for file at: ".$cache_path);
return;
}
fclose($fp);
</pre>
<div class='alert alert-success'>
也許有多個使用者同時瀏覽同一個網頁，如此會導致同時寫入同一個cache檔、cache內容錯亂。<br/>
所以這邊用flock的獨占鎖定去佔有檔案，先搶先贏。
</div>
<pre class="brush: php">
@chmod($cache_path, FILE_WRITE_MODE);
</pre>
<div class='alert alert-success'>
之後會更新這隻快取檔即可，不用再建立一次，所以把檔案設成可寫入。
</div>
<pre class="brush: php">
log_message('debug', "Cache file written: ".$cache_path);
}
// --------------------------------------------------------------------
/**
* Update/serve a cached file
*
* @access public
* @param object config class
* @param object uri class
* @return void
*/
function _display_cache(&$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;
$filepath = $cache_path.md5($uri);
if ( ! @file_exists($filepath))
{
return FALSE;
}
if ( ! $fp = @fopen($filepath, FOPEN_READ))
{
return FALSE;
}
flock($fp, LOCK_SH);
$cache = '';
if (filesize($filepath) > 0)
{
$cache = fread($fp, filesize($filepath));
}
flock($fp, LOCK_UN);
fclose($fp);
// Strip out the embedded timestamp
if ( ! preg_match("/(\d+TS--->)/", $cache, $match))
{
return FALSE;
}
// Has the file expired? If so we'll delete it.
if (time() >= trim(str_replace('TS--->', '', $match['1'])))
{
if (is_really_writable($cache_path))
{
@unlink($filepath);
log_message('debug', "Cache file has expired. File deleted");
return FALSE;
}
}
// Display the cache
$this->_display(str_replace($match['0'], '', $cache));
log_message('debug', "Cache file is current. Sending it to browser.");
return TRUE;
}
</pre>
<div class='alert alert-success'>
明明是回傳布林值，怎麼註解會寫return void的呢。滿多地方有這個瑕疵。<br/>
</div>
<div class='alert alert-danger'>
再次為濫用全域變數、全域函數、以及自定義載入功能付出代價。<br/>
傳入的參數是(&$CFG, &$URI)，需要取址運算符。<br/>
這讓這段code更難理解與維護了，不是嗎？<br/>
要傳入config與uri相關參數並不困難，在類別建構時傳入即可，實在沒必要寫這麼醜。<br/>
但因為自訂了load_class函數來載入全部類別，導致了現在醜code的結果。<br/>
請參見：<a href='common.html'>貫穿全部：core/common.php</a>中，我對於load_class函數的批評。
</div>
<pre class="brush: php">
}
// END Output Class
/* End of file Output.php */
/* Location: ./system/core/Output.php */
</pre>
<div class='alert alert-danger'>
技術債會導致更多的技術債需要還。<br/>
為了配合最一開始load_class這種又髒又快的workaroud寫法，Output類別必須寫出對應的醜寫法。<br/>
除此之外，也導致Output類別嚴重相依在CI之下，無法獨立使用。<br/>
</div>
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