~~~
<?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
*/
// ------------------------------------------------------------------------
/**
* CodeIgniter Benchmark Class
*
* This class enables 能够 you to mark points and calculate 计算 the time difference 差异
* between them. Memory consumption can also be displayed.
*
* @package CodeIgniter
* @subpackage Libraries
* @category Libraries
* @author ExpressionEngine Dev Team
* @link http://codeigniter.com/user_guide/libraries/benchmark.html
*/
class CI_Benchmark {
/**
* List of all benchmark markers and when they were added
* 用来存储基准测试类标记的数组
* @var array
*/
var $marker = array();
// --------------------------------------------------------------------
/**
* Set a benchmark marker
* 设置一个标记点
* Multiple calls to this function can be made so that several
* execution points can be timed
*
* @access public
* @param string $name name of the marker
* @return void
*/
function mark($name)
{
// 在程序的任意地方调用方法时，会记录当前的时间点。
$this->marker[$name] = microtime();
}
// --------------------------------------------------------------------
/**
* Calculates the time difference between two marked points.
* 计算出两个时间点之间的时间。
* If the first parameter is empty this function instead returns the
* {elapsed_time} pseudo-variable 虚假变量. This permits 许可 the full system
* execution time to be shown in a template. The output class will
* swap the real value for this variable.
*
* @access public
* @param string a particular marked point
* @param string a particular marked point
* @param integer the number of decimal places
* @return mixed
*/
function elapsed_time($point1 = '', $point2 = '', $decimals = 4)
{
/*
* 如果没有给出明确的时间点，那么会计算出整个程序运行的时间。
* 怎么可以做到计算出整个程序的运行时间的呢？其实执行此计算的是Output组件。
* 而调用Benchmark::elapsed_time();（无参数）的时候，实质上先返回的并不是
* 整个程序运行的时间，也不可能做到，实质返回的是一个{elapsed_time}标签，然后
* Output在处理输出的时候，再计算出整个程序运行时间，因为处理输出阶段程序可以视
* 为处于最后阶段，于是可以近似计算出总时间，然后把输出中的{elapsed_time}替换掉。
* 下面的memory_usage()原理相同。
*/
if ($point1 == '')
{
return '{elapsed_time}';
}
if ( ! isset($this->marker[$point1]))
{
return '';
}
if ( ! isset($this->marker[$point2]))
{
$this->marker[$point2] = microtime();
}
//这里为什么要用到list，是因为microtime();返回值是“msec sec”的格式。
list($sm, $ss) = explode(' ', $this->marker[$point1]);
list($em, $es) = explode(' ', $this->marker[$point2]);
return number_format(($em + $es) - ($sm + $ss), $decimals);
}
// --------------------------------------------------------------------
/**
* Memory Usage
*
* This function returns the {memory_usage} pseudo-variable.
* This permits it to be put it anywhere in a template
* without the memory being calculated until the end.
* The output class will swap the real value for this variable.
*
* @access public
* @return string
*/
function memory_usage()
{
return '{memory_usage}';
}
}
// END CI_Benchmark class
/* End of file Benchmark.php */
/* Location: ./system/core/Benchmark.php */
~~~
