~~~
<?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 负责 for sending final output to browser
* 负责把最终的输出发送到浏览器
* @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
* 当前输出的字符串
*
* @var string
* @access protected
*/
protected $final_output;
/**
* Cache expiration time
* 缓存终结的时间
* @var int
* @access protected
*/
protected $cache_expiration = 0;
/**
* List of server headers
* 服务器头列表
* @var array
* @access protected
*/
protected $headers = array();
/**
* List of mime types
*
* @var array
* @access protected
*/
protected $mime_types = array();
/**
* Determines wether profiler is enabled
* 是否启用分析器
* @var book
* @access protected
*/
protected $enable_profiler = FALSE;
/**
* Determines if output compression is enabled
* 是否开启输出压缩
* @var bool
* @access protected
*/
protected $_zlib_oc = FALSE;
/**
* List of profiler sections
* 分析器列表
*
* @var array
* @access protected
*/
protected $_profiler_sections = array();
/**
* Whether or not to parse variables like {elapsed_time} and {memory_usage}
* 是否解析变量{elapsed_time} and {memory_usage}
* 注意文档说这里有错误详见http://codeigniter.org.cn/user_guide/libraries/output.html
* 最下方
* @var bool
* @access protected
*/
protected $parse_exec_vars = TRUE;
/**
* Constructor
*
*/
function __construct()
{
// 返回配置项zlib.output_compression的值并赋给$this->_zlib_oc
// 如果配置项中开启了输出压缩功能则 $this->_zlib_oc 的值为on
$this->_zlib_oc = @ini_get('zlib.output_compression');
// Get mime types for later
// 获取mimetype
if (defined('ENVIRONMENT') AND file_exists(APPPATH.'config/'.ENVIRONMENT.'/mimes.php'))
{
include APPPATH.'config/'.ENVIRONMENT.'/mimes.php';
}
else
{
include APPPATH.'config/mimes.php';
}
// $mimes 是mimes.php中定义的一个数组
$this->mime_types = $mimes;
log_message('debug', "Output Class Initialized");
}
// --------------------------------------------------------------------
/**
* Get Output
* 使用这个方法，你可以得到将要输出的数据，并把它保存起来
* Returns the current output string
* 返回当前输出的字符串
* @access public
* @return string
*/
function get_output()
{
return $this->final_output;
}
// --------------------------------------------------------------------
/**
* Set Output
*
* Sets the output string
* 设置输出的字符串
* @access public
* @param string
* @return void
*/
function set_output($output)
{
$this->final_output = $output;
return $this;
}
// --------------------------------------------------------------------
/**
* Append Output
* 在最终输出字符串后，追加数据
* Appends data onto the output string
*
* @access public
* @param string
* @return void
*/
function append_output($output)
{
if ($this->final_output == '')
{
$this->final_output = $output;
}
else
{
$this->final_output .= $output;
}
return $this;
}
// --------------------------------------------------------------------
/**
* Set Header
* 使用此方法，允许你设置将会被发送到浏览器的HTTP协议的标头，作用相当于php的标准函数: header()。
* Lets you set a server header which will be outputted with the final display.
* 允许您设置一个服务器头用于最终的显示输出。
* Note: If a file is cached, headers will not be sent. We need to figure 计算 out
* how to permit header data to be saved with the cache data...
*
* @access public
* @param string
* @param bool
* @return void
*/
function set_header($header, $replace = TRUE)
{
// If zlib.output_compression is enabled it will compress the output,
// but it will not modify the content-length header to compensate 补偿 for
// the reduction减少 还原, causing the browser to hang waiting for more data.
// We'll just skip content-length in those cases.
if ($this->_zlib_oc && strncasecmp($header, 'content-length', 14) == 0)
{
return;
}
$this->headers[] = array($header, $replace);
return $this;
}
// --------------------------------------------------------------------
/**
* Set Content Type Header
* 设置Content-Type
* @access public
* @param string extension of the file we're outputting
* @return void
*/
function set_content_type($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 $this;
}
// --------------------------------------------------------------------
/**
* Set HTTP Status Header
* moved to Common procedural functions in 1.7.2
* 允许你手动设置服务器状态头(header)
* @access public
* @param int the status code
* @param string
* @return void
*/
function set_status_header($code = 200, $text = '')
{
set_status_header($code, $text);
return $this;
}
// --------------------------------------------------------------------
/**
* Enable/disable Profiler
* 允许你开启或禁用分析器
* @access public
* @param bool
* @return void
*/
function enable_profiler($val = TRUE)
{
$this->enable_profiler = (is_bool($val)) ? $val : TRUE;
return $this;
}
// --------------------------------------------------------------------
/**
* Set Profiler Sections
* 设置$this->_profiler_sections
* Allows override of default / config settings for Profiler section display
* 允许你在评测器启用时，控制(开/关)其特定部分
*
* @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
* 设置缓存以及缓存时间
* @access public
* @param integer 其中 $time 是你希望缓存更新的 分钟 数
* @return void
*/
function cache($time)
{
$this->cache_expiration = ( ! is_numeric($time)) ? 0 : $time;
return $this;
}
// --------------------------------------------------------------------
/**
* Display Output
* 显示输出
* 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 $CI =& get_instance()
// since this function is sometimes called by the caching mechanism,
// which happens before the CI super object is available.
// 注意：我们使用global 是因为我们不能使用$CI =& get_instance()
global $BM, $CFG;
// Grab the super object if we can.
// //当然如果可以拿到超级控制器，我们先拿过来。
if (class_exists('CI_Controller'))
{
$CI =& get_instance();
}
// --------------------------------------------------------------------
// Set the output data
// 设置输出数据
if ($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 $CI object above
// 如果缓存时间>0 ，$CI 超级对象存在并且超级对象下面存在_output 方法
// 调用_write_cache 方法，写一个缓存文件
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
// 计算代码执行时间和内存使用时间
$elapsed = $BM->elapsed_time('total_execution_time_start', 'total_execution_time_end');
// 如果$this->parse_exec_vars为true，将输出中的{elapsed_time}，{memory_usage}
// 替换为计算出的时间。
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, $output);
}
// --------------------------------------------------------------------
// Is compression requested?压缩传输的处理。
if ($CFG->item('compress_output') === TRUE && $this->_zlib_oc == FALSE)
{
if (extension_loaded('zlib'))
{
if (isset($_SERVER['HTTP_ACCEPT_ENCODING']) AND strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE)
{
ob_start('ob_gzhandler');
}
}
}
// --------------------------------------------------------------------
// Are there any server headers to send?
// 有没有服务器头发送？
if (count($this->headers) > 0)
{
foreach ($this->headers as $header)
{
@header($header[0], $header[1]);
}
}
// --------------------------------------------------------------------
// Does the $CI object exist?
// If not we know we are dealing with a cache file so we'll
// simply echo out the data and exit.
// 如果没有$CI就证明当前是一个缓存的输出，我们只简单的发送数据并退出
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.
// 如果开启了性能分析我们就调用，
// 会生成一些报告到页面尾部用于辅助我们调试。
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
// 如果存在</body></html>标签，我们将删除，插入我们的性能分析代码后再添加回去
if (preg_match("|</body>.*?</html>|is", $output))
{
$output = preg_replace("|</body>.*?</html>|is", '', $output);
$output .= $CI->profiler->run();
$output .= '</body></html>';
}
else
{
$output .= $CI->profiler->run();
}
}
// --------------------------------------------------------------------
// Does the controller contain a function named _output()?
// If so send the output there. Otherwise, echo it.
// 如果控制器中有_output 这个方法我们直接调用
// 如果没有直接发送数据到浏览器
if (method_exists($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);
}
// --------------------------------------------------------------------
/**
* Write a Cache File
* 生成一个缓存文件
* @access public
* @param string
* @return void
*/
function _write_cache($output)
{
// 调用超级对象
$CI =& get_instance();
// 找到缓存路径
$path = $CI->config->item('cache_path');
$cache_path = ($path == '') ? APPPATH.'cache/' : $path;
// 如果缓存路径不是一个文件夹或者不可写 ，报错返回。
if ( ! is_dir($cache_path) OR ! is_really_writable($cache_path))
{
log_message('error', "Unable to write cache file: ".$cache_path);
return;
}
// 获取$uri
$uri = $CI->config->item('base_url').
$CI->config->item('index_page').
$CI->uri->uri_string();
// 生成缓存文件。
$cache_path .= md5($uri);
if ( ! $fp = @fopen($cache_path, FOPEN_WRITE_CREATE_DESTRUCTIVE))
{
log_message('error', "Unable to write cache file: ".$cache_path);
return;
}
// 计算缓存文件过期时间。
$expire = time() + ($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($fp);
@chmod($cache_path, FILE_WRITE_MODE);
log_message('debug', "Cache file written: ".$cache_path);
}
// --------------------------------------------------------------------
/**
* Update/serve a cached file
* 在CodeIgniter.php里面有调用此方法，此方法是负责缓存的输出，
* 如果在CodeIgniter.php中调用此方法有输出，则
* 本次请求的运行将直接结束，直接以缓存输出作为响应。
*
* @access public
* @param object config class
* @param object uri class
* @return void
*/
function _display_cache(&$CFG, &$URI)
{
// 取得保存缓存的路径
$cache_path = ($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
// 一条准确的路由都会对应一个缓存文件，缓存文件是对应路由字符串的md5密文。
$uri = $CFG->item('base_url').
$CFG->item('index_page').
$URI->uri_string;
$filepath = $cache_path.md5($uri);
// 如果没有此缓存文件，获取缓存内容失败，则可以返回FALSE。
if ( ! @file_exists($filepath))
{
return FALSE;
}
// 如果有此缓存文件，但是无法读，获取缓存内容失败，同样返回FALSE。
if ( ! $fp = @fopen($filepath, FOPEN_READ))
{
return FALSE;
}
// 打开到缓存文件，并以$fp作为句柄。下一步先取得共享锁（读取）。
flock($fp, LOCK_SH);
$cache = '';
if (filesize($filepath) > 0)
{
$cache = fread($fp, filesize($filepath));
}
// 解锁
flock($fp, LOCK_UN);
// 关闭文件连接。
fclose($fp);
// 下面这个TS--->字样，只是因为CI的缓存文件里面的内容
// 是规定以数字＋TS--->开头而已。这个数字是代表创建时间。
// 如果不符合此结构，可视为非CI的缓存文件，或者文件已损坏，
// 获取缓存内容失败，返回FALSE。
// Strip out the embedded timestamp
if ( ! preg_match("/(\d+TS--->)/", $cache, $match))
{
return FALSE;
}
// Has the file expired? If so we'll delete it.
// 判断缓存是否过期，如果过期我们将删除它
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;
}
}
// END Output Class
/* End of file Output.php */
/* Location: ./system/core/Output.php */
~~~
