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。