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。