CI核心文件分析之基准测试类 （Benchmark.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
*/

// ------------------------------------------------------------------------

/**
* CodeIgniter Benchmark Class
*
* This class enables you to mark points and calculate the time difference
* 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
*
* @var array
*/
var $marker = array();

// --------------------------------------------------------------------

/**
* Set a benchmark marker
*
* 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)
{
$this->marker[$name] = microtime();
}

// --------------------------------------------------------------------

/**
* Calculates the time difference between two marked points.
*
* If the first parameter is empty this function instead returns the
* {elapsed_time} pseudo-variable. This permits 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 = '', $decimals = 4)
{
if ($point1 == '')
{
return '{elapsed_time}';
}

if ( ! isset($this->marker[$point1]))
{
return '';
}

if ( ! isset($this->marker[$point2]))
{
$this->marker[$point2] = microtime();
}

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 */

看了下源码，主要通过elapsed_time()函数计算二个时间点的时间间隔；通过

list($sm, $ss) = explode(' ', $this->marker[$point1]);
list($em, $es) = explode(' ', $this->marker[$point2]);

return number_format(($em + $es) - ($sm + $ss), $decimals);

方式返回时间间隔。

备注：microtime() 当前 Unix 时间戳以及微秒数。本函数以 "msec sec" 的格式返回一个字符串，其中 sec 是自 Unix 纪元（0:00:00 January 1, 1970 GMT）起到现在的秒数，msec 是微秒部分。字符串的两部分都是以秒为单位返回的。