Output组件负责向浏览器发送最终输出，是ci框架中使用非常广泛的一个组件，在之前的几篇源码阅读中，也使用到了这个组件，例如：load->view() 在阅读输出组件源码的时候，我们主要关注以下几个问题：
- Output是如何输出页面的，在最终输出的之前做了哪些处理？
- 页面缓存是怎么实现的？
1.构造函数
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 = (extension_loaded('mbstring') && ini_get('mbstring.func_overload'));
// Get mime types for later
$this->mimes =& get_mimes();
log_message('info', 'Output Class Initialized');
}
这个构造函数中一共做了三件事：
- 判断是否可以压缩输出内容，这是为了在之后的输出缓存中决定是否压缩；
- mbstring是否可以重载，因为ci框架中对mbstring标准库的一些函数进行了重载，而输出组件中正好要使用重载的函数，详细了解可以查看’./system/core/compat/mbstring.php’文件；
- ci框架中定义了一个mimes列表，将mimes列表取出，为了之后设置请求头时使用；
从构造函数中我们可以看出，output在输出内容之前，会对要输出的内容进行压缩。
2.输出函数——_display()
/**
* 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);
}
这里主要注意的是压缩问题。
- $_SERVER[‘HTTP_ACCEPT_ENCODING’]是判断客户端是否支持压缩
- 如果支持压缩且需要执行php压缩代码，如果是缓存，发送相应请求头，不是缓存，执行php的压缩代码
- 如果不支持压缩，如果是缓存，则在执行php的解压缩代码再输出（因为缓存的内容会进行压缩），不是缓存，不执行压缩代码
3.写缓存_write_cache
缓存的目录可以是自定义目录，默认是’application/cache’目录
$path = $CI->config->item('cache_path');
$cache_path = ($path === '') ? APPPATH.'cache/' : $path;
缓存的key是根据uri信息生成的md5字符串
$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);
$this->_compress_output为true对输出内容执行php压缩代码
if ($this->_compress_output === TRUE)
{
$output = gzencode($output);
if ($this->get_header('content-type') === NULL)
{
$this->set_content_type($this->mime_type);
}
}
缓存有效时间以秒为单位，缓存有效时间和请求头信息，以序列化后的数组存入缓存中，并以’ENDCI—>’字符串为分割符合输出内容分开
$expire = time() + ($this->cache_expiration * 60);
// Put together our serialized info.
$cache_info = serialize(array(
'expire' => $expire,
'headers' => $this->headers
));
$output = $cache_info.'ENDCI--->'.$output;
最后将缓存内容写入缓存文件
/**
* 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'], $expire);
}
4.输出缓存内容——_display_cache函数
_display_cache会通过Key找到对应的缓存文件，然后取出缓存文件中的内容，查看缓存信息，反序列化缓存信息，得到缓存有效时间，判断缓存是否有效，无效则删除缓存，返回FALSE *$_SERVER[‘REQUEST_TIME’]参数是请求时间
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;
}
设置缓存请求头
// 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]);
}
输出缓存 在阅读CodeIngiter.php的时候，我们知道，如果对应请求有缓存的话，则不会初始化控制器，所以_display就是通过是否加载了控制器来判断输出的内容是不是缓存的
// Display the cache
$this->_display(self::substr($cache, self::strlen($match[0])));
/**
* Update/serve cached output
*
* @uses CI_Config
* @uses CI_URI
*
* @param object &$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;
}
5.设置缓存请求头——set_cache_header函数
/**
* 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');
}