CodeIgniter(CI)缓存分析

最新推荐文章于 2021-03-27 03:58:53 发布

原创最新推荐文章于 2021-03-27 03:58:53 发布 · 2.2k 阅读

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#CI缓存 #CodeIgniter缓存

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本文深入探讨了CodeIgniter中的缓存机制，包括如何启用缓存、配置缓存路径、缓存文件的创建与删除流程，以及缓存系统的内部实现原理。

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codeigniter 中的缓存系统分析

ci中自带了一套自己的缓存系统这套缓存系统

使用方法如下：
只需要在controller或是model之中打开model中打开即可 
$this->output->cache( 3 );//缓存时间为3分钟

关于cache的配置项
位于config/config.php文件中
$config[ 'cache_path' ] = '';//设置文件路径

从CodeIgniter.php文件里可以看出缓存的使用过程

首先进入这里

/*
   文件：CodeIgniter.php
 * ------------------------------------------------------
 *  Instantiate the output class
 * ------------------------------------------------------
 */

$OUT =& load_class('Output', 'core');

/*
 * ------------------------------------------------------
 *	Is there a valid cache file?  If so, we're done...
 * ------------------------------------------------------
 */

if( $EXT->_call_hook( 'cache_override' ) === FALSE )
{
	if ($OUT->_display_cache($CFG, $URI) == TRUE)//使用缓存文件或是删除过期文件
	{
		exit;
	}
}


/**
 * Output.php
 * Update/serve a cached file
 * 使用缓存文件 删除过期的文件
 * @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;//

}
以下代码显示输出（在未使用cache文件或cache文件过期情况下）

/* CodeIgniter.php
 * ------------------------------------------------------
 *  Send the final rendered output to the browser
 * ------------------------------------------------------
 */

if ($EXT->_call_hook('display_override') === FALSE)
{
	$OUT->_display();
}

若存在$this->output->cache( n ); //n > 0;

/**
		 *  Output.php
 * Set Cache
 *
 * @access	public
 * @param	integer
 * @return	void
 */
function cache($time)
{
	$this->cache_expiration = ( ! is_numeric($time)) ? 0 : $time;

	return $this;
}

	  如果设置了缓存时间则需要写cache文件

//Output.php

// 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);
}

//Output.php
function _write_cache($output)
{//写缓存文件
	$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();
	$cache_path .= md5($uri);
	if ( ! $fp = @fopen($cache_path, FOPEN_WRITE_CREATE_DESTRUCTIVE))
	{
		log_message('error', "Unable to write cache file: ".$cache_path);
		return;
	}
	$expire = time() + ($this->cache_expiration * 60);
	if (flock($fp, LOCK_EX))
	{
		fwrite($fp, $expire.'TS--->'.$output);//写缓存文件
		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);
}