UTF-8 bit by bit (2001)

栏目: IT技术 · 发布时间: 4年前

内容简介:Richard Suchenwirth 2001-02-28 - From a delightful debugging chat at theTcl chatroom, I was brought to write down what I think on UTF-8 analysis (cf.Unicode and UTF-8, see also).I imagine a UTF-8 string as a railroad. It operates single-unitThe xxxxx bits

Richard Suchenwirth 2001-02-28 - From a delightful debugging chat at theTcl chatroom, I was brought to write down what I think on UTF-8 analysis (cf.Unicode and UTF-8, see also).

I imagine a UTF-8 string as a railroad. It operates single-unit railcars (one-byte ASCII characters, to be known from the fact that the highest bit is 0), and trains (sequences of two or more bytes that together form a character). Each train consists of exactly one locomotive (you see I'm European) and one or more trailers . The locomotive indicates the length of the train, including itself, in the highest bits that form a consecutive row of 1's, and one 0 bit. Examples:

0xxxxxxx : I'm a railcar, just a single unit
 110xxxxx : I'm leading a train of length 2

The xxxxx bits are used for other purposes (locomotives carry some freight too ;-)

Trailers indicate that they are trailers by the initial bit sequence 10. This way, they can't be mistaken for railcars or locomotives. E.g.

10yyyyyy: I'm a trailer

The freight of the train is in the x's and y's. In that concrete case, a C program reported to have received the bytes C3 and A4. Written as binary, that's

Now for clarity we delimit the indicators with parens:

(110)00011 (10)100100

and can just remove them:

00011 100100
 11100100 => E4, the iso8859-1 value for German ä ("a umlaut").

The generalized rule for the indicator of each byte is "those bits from highest(leftmost) down, up to and including the first zero bit".

Now going the other way. In orthodox UTF-8, a NUL byte (\x00) is represented by a NUL byte. Plain enough. But in Tcl we sometimes want NUL bytes inside "binary" strings (e.g. image data), without them terminating it as a real NUL byte does. To represent a NUL byte without any physical NUL bytes, we treat it like a character above ASCII, which must be a minimum two bytes long:

(110)00000 (10)000000 => C0 80

Whoops. Took us a while, but now we can read UTF-8, bit by bit.

andrewsh 2010-03-12 - Please note that 0xc0 0x80 sequence is illegal in the "Real" UTF-8: [], []


以上就是本文的全部内容,希望本文的内容对大家的学习或者工作能带来一定的帮助,也希望大家多多支持 码农网

查看所有标签

猜你喜欢:

本站部分资源来源于网络,本站转载出于传递更多信息之目的,版权归原作者或者来源机构所有,如转载稿涉及版权问题,请联系我们

深入浅出Struts 2

深入浅出Struts 2

Budi Kuniawan / 杨涛、王建桥、杨晓云 / 人民邮电出版社 / 2009-04 / 59.00元

本书是广受赞誉的Struts 2优秀教程,它全面而深入地阐述了Struts 2的各个特性,并指导开发人员如何根据遇到的问题对症下药,选择使用最合适的特性。作者处处从实战出发,在丰富的示例中直观地探讨了许多实用的技术,如数据类型转换、文件上传和下载、提高Struts 2应用的安全性、调试与性能分析、FreeMarker、Velocity、Ajax,等等。跟随作者一道深入Struts 2,聆听大量来之......一起来看看 《深入浅出Struts 2》 这本书的介绍吧!

XML、JSON 在线转换
XML、JSON 在线转换

在线XML、JSON转换工具

html转js在线工具
html转js在线工具

html转js在线工具

RGB HSV 转换
RGB HSV 转换

RGB HSV 互转工具