CodeIgniter框架源码学习之utf-8编码的环境支持类－－Utf8.php

文件位置：./system/core/Utf8.php

<?php

/**

* CodeIgniter

*

* An open source application development framework for PHP

*

* This content is released under the MIT License (MIT)

*

* Copyright (c) 2014 - 2017, British Columbia Institute of Technology

*

* Permission is hereby granted, free of charge, to any person obtaining a copy

* of this software and associated documentation files (the "Software"), to deal

* in the Software without restriction, including without limitation the rights

* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

* copies of the Software, and to permit persons to whom the Software is

* furnished to do so, subject to the following conditions:

*

* The above copyright notice and this permission notice shall be included in

* all copies or substantial portions of the Software.

*

* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

* THE SOFTWARE.

*

* @package CodeIgniter

* @author EllisLab Dev Team

* @copyright Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)

* @copyright Copyright (c) 2014 - 2017, British Columbia Institute of Technology (http://bcit.ca/)

* @license http://opensource.org/licenses/MIT MIT License

* @link https://codeigniter.com

* @since Version 2.0.0

* @filesource

*/

defined('BASEPATH') OR exit('No direct script access allowed');

/**

* Utf8 Class

*

* Provides support for UTF-8 environments

*提供UTF-8环境支持

* @package CodeIgniter

* @subpackage Libraries

* @category UTF-8

* @author EllisLab Dev Team

* @link https://codeigniter.com/user_guide/libraries/utf8.html

*/

class CI_Utf8 {

/**

* Class constructor

*

* Determines if UTF-8 support is to be enabled.

*确定是否支持UTF-8

* @return void

*/

public function __construct()

{

if (

判断如果正则表达式支持utf8，iconv库已经安装，多字节字符串函数重载没有启用，应用程序字  符集是utf8

defined('PREG_BAD_UTF8_ERROR') // PCRE must support UTF-8

&& (ICONV_ENABLED === TRUE OR MB_ENABLED === TRUE) // iconv or mbstring must be installed

&& strtoupper(config_item('charset')) === 'UTF-8' // Application charset must be UTF-8

)

{

define('UTF8_ENABLED', TRUE);

log_message('debug', 'UTF-8 Support Enabled');

}

else

{

define('UTF8_ENABLED', FALSE);

log_message('debug', 'UTF-8 Support Disabled');

}

log_message('info', 'Utf8 Class Initialized');

}

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

/**

* Clean UTF-8 strings

* 清理utf8编码的字符串

* Ensures strings contain only valid UTF-8 characters.

*

* @param string $str String to clean

* @return string

*/

public function clean_string($str)

{

(1)判断如果字符串不是ASCII码

(2)使用iconv函数将字符串转码（关于iconv函数详情见http://www.php.net/manual/zh/function.iconv.php）

(3)返回字符串

if ($this->is_ascii($str) === FALSE)

{

if (MB_ENABLED)

{

$str = mb_convert_encoding($str, 'UTF-8', 'UTF-8');

}

elseif (ICONV_ENABLED)

{

$str = @iconv('UTF-8', 'UTF-8//IGNORE', $str);

}

}

return $str;

}

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

/**

* Remove ASCII control characters

* 删除所有在xml中可能导致问题的ASCII码字符，除了水平制表符，换行，回车。

(1) 直接调用remove_invisible_characters()来删除无效的字符并返回。

注：remove_invisible_characters 函数在common.php中定义

* Removes all ASCII control characters except horizontal tabs,

* line feeds, and carriage returns, as all others can cause

* problems in XML.

*

* @param string $str String to clean

* @return string

*/

public function safe_ascii_for_xml($str)

{

return remove_invisible_characters($str, FALSE);

}

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

/**

* Convert to UTF-8

*

* Attempts to convert a string to UTF-8.

*将字符串转换为utf8编码

(1)如果iconv函数存在，使用iconv转换

(2)如果mb_convert_encoding函数存在，使用mb_convert_encoding函数转换

(3)如果上面两个函数都不存在则不能转换返回false

(4)如果转换完成返回转换后的字符串

* @param string $str Input string

* @param string $encoding Input encoding

* @return string $str encoded in UTF-8 or FALSE on failure

*/

public function convert_to_utf8($str, $encoding)

{

if (MB_ENABLED)

{

return mb_convert_encoding($str, 'UTF-8', $encoding);

}

elseif (ICONV_ENABLED)

{

return @iconv($encoding, 'UTF-8', $str);

}

return FALSE;

}

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

/**

* Is ASCII?

*

* Tests if a string is standard 7-bit ASCII or not.

*  测试一个字符串是不是ASCII码

(1) 使用正则拼配返回测试结果。

* @param string $str String to check

* @return bool

*/

public function is_ascii($str)

{

return (preg_match('/[^\x00-\x7F]/S', $str) === 0);

}

}