UTF16,即是通常所说的Unicode。
其实把UTF16叫成Unicode不太合适,容易给人造成混乱。因为Unicode是字符集,而不是实际的存储编码方案。
UTF16是 变长 编码方案。
比如Unicode code point为2F92B的字,把它保存成UTF16(也就是Windows XP记事本中的Unicode),就变成了FC D8 2B DD,如果是 Big endian 的话就应该是D8 FC DD 2B。这个值是怎么来的?
对于 0-FFFF 的Unicode字符,UTF16中用一个两个字节的Unicode code point直接表示。对于 10000-10FFFF 的Unicode字符,UTF16中用surrogate pair表示,既用两个字符表示,它们之间的转换过程是:
下面把code point为U+64321(十六进制)的Unicode字符编码成UTF-16,由于它大于U+FFFF,所以它要编码成surrogate pair:
一点问题:
.net framework平台下,string类型变量name包含两个字符,一个是0-FFFF的字符,另一个是10000-10FFFF的字符,那么name的长度将是3而不是2,因为name有6个字节。
UTF16是 变长 编码方案。
比如Unicode code point为2F92B的字,把它保存成UTF16(也就是Windows XP记事本中的Unicode),就变成了FC D8 2B DD,如果是 Big endian 的话就应该是D8 FC DD 2B。这个值是怎么来的?
对于 0-FFFF 的Unicode字符,UTF16中用一个两个字节的Unicode code point直接表示。对于 10000-10FFFF 的Unicode字符,UTF16中用surrogate pair表示,既用两个字符表示,它们之间的转换过程是:
下面把code point为U+64321(十六进制)的Unicode字符编码成UTF-16,由于它大于U+FFFF,所以它要编码成surrogate pair:
v = 0x64321详细描述:
v′ = v - 0x10000
= 0x54321
= 0101 0100 0011 0010 0001
vh = 0101010000 // higher 10 bits of v′
vl = 1100100001 // lower 10 bits of v′
w1 = 0xD800 // the resulting 1st word is initialized with the high bits
w2 = 0xDC00 // the resulting 2nd word is initialized with the low bits
w1 = w1 | vh
= 1101 1000 0000 0000 |
01 0101 0000
= 1101 1001 0101 0000
= 0xD950
w2 = w2 | vl
= 1101 1100 0000 0000 |
11 0010 0001
= 1101 1111 0010 0001
= 0xDF21
The improvement that UTF-16 made over UCS-2 is its ability to encode characters in planes 1–16, not just those in plane 0 (BMP).
UTF-16 represents non-BMP characters (those from U+10000 through U+10FFFF) using a pair of 16-bit words, known as a
surrogate pair. First 10000
16 is subtracted from the code point to give a 20-bit value. This is then split into two separate 10-bit values each of which is represented as a surrogate with the most significant half placed in the first surrogate. To allow safe use of simple
word-oriented string processing, separate ranges of values are used for the two surrogates: 0xD800–0xDBFF for the first, most significant surrogate and 0xDC00-0xDFFF for the second, least significant surrogate.
For example, the character at code point U+10000 becomes the code unit sequence 0xD800 0xDC00, and the character at U+10FFFD, the upper limit of Unicode, becomes the sequence 0xDBFF 0xDFFD. Unicode and ISO/IEC 10646 do not, and will never, assign characters to any of the code points in the U+D800–U+DFFF range, so an individual code value from a surrogate pair does not ever represent a character.
我们可以用Windows自带的计算器的科学计算模式完成上述计算,当然也可以自己写个小程序:)
要输入10000-10FFFF的字符,可以使用微软拼音输入法。它有一项以Unicode码输入字符的功能。
要显示这些字符中的汉字部分,可以安装Unifont,参见海峰五笔的网站。
关于编码知识,可以google一下这一系列文章,写的非常精彩:“Java中的字符集编码入门”
我们可以用Windows自带的计算器的科学计算模式完成上述计算,当然也可以自己写个小程序:)
要输入10000-10FFFF的字符,可以使用微软拼音输入法。它有一项以Unicode码输入字符的功能。
要显示这些字符中的汉字部分,可以安装Unifont,参见海峰五笔的网站。
关于编码知识,可以google一下这一系列文章,写的非常精彩:“Java中的字符集编码入门”
一点问题:
.net framework平台下,string类型变量name包含两个字符,一个是0-FFFF的字符,另一个是10000-10FFFF的字符,那么name的长度将是3而不是2,因为name有6个字节。
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace CodePoint2UTF16
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void btnConvert_Click( object sender, EventArgs e)
{
String cp = tbUnicodeCodePoint.Text.Trim();
try
{
int n = Convert.ToInt32(cp, 16);
if (n < 0 || n > 0x10FFFF)
{
MessageBox.Show(cp + " is not in 0x0 - 0x10FFFF");
return;
}
if (n < 0x10000)
{
tbUTF16Code.Text = Convert.ToString(n, 16);
return;
}
else
{
n -= 0x10000;
int h = n >> 10;
int l = n & 0x3FF;
h |= 0xD800;
l |= 0xDC00;
tbUTF16Code.Text = Convert.ToString(h, 16) + " " + Convert.ToString(l, 16);
}
}
catch (Exception ex)
{
MessageBox.Show( "Invalid text: " + cp + Environment.NewLine + ex.Message);
}
}
}
}
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
namespace CodePoint2UTF16
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void btnConvert_Click( object sender, EventArgs e)
{
String cp = tbUnicodeCodePoint.Text.Trim();
try
{
int n = Convert.ToInt32(cp, 16);
if (n < 0 || n > 0x10FFFF)
{
MessageBox.Show(cp + " is not in 0x0 - 0x10FFFF");
return;
}
if (n < 0x10000)
{
tbUTF16Code.Text = Convert.ToString(n, 16);
return;
}
else
{
n -= 0x10000;
int h = n >> 10;
int l = n & 0x3FF;
h |= 0xD800;
l |= 0xDC00;
tbUTF16Code.Text = Convert.ToString(h, 16) + " " + Convert.ToString(l, 16);
}
}
catch (Exception ex)
{
MessageBox.Show( "Invalid text: " + cp + Environment.NewLine + ex.Message);
}
}
}
}
本文转自 h2appy 51CTO博客,原文链接:http://blog.51cto.com/h2appy/144639,如需转载请自行联系原作者