Character Encodings For Modern Programmers

http://blog.gatunka.com/2014/04/25/character-encodings-for-modern-programmers/

by nkurz • 12 years ago

83 12 12 years ago

blog.gatunka.com

sheetjs2• 12 years ago

Fun facts:

- a few code pages (such as CP864 DOS Arabic) use the arabic percent sign ٪ (0x066A) at codepoint 0x25 instead of the standard ANSI %.

- Mozilla Firefox and Thunderbird approximate the Arabic codepages (including ASMO-708) to ISO-8869-6, which breaks XLS parsing from files generated from certain international versions of Excel (which actually forced me to build a library for the various character encodings: https://github.com/SheetJS/js-codepage)

alister2• 12 years ago

More fun facts:

- We went from 128 ASCII characters to 110,187 currently-assigned Unicode characters (or Encoded Character code points, to use precise language)[1]. That's a thousand-fold increase. Who would have thought we'd need so many!

- Unicode can represent 1,114,112 code points. So there's lots of room for yet more.

[1] http://babelstone.blogspot.ca/2005/11/how-many-unicode-chara...

MichaelGG2• 12 years ago

It's like there should be an encoding which specifies the intent. Unless the Arabic percent sign (which looks like ANSI but flipped?) has some other semantics, why shouldn't Excel handle both of them? Other than that there could be 100 different percent signs.

sheetjs2• 12 years ago

The strings are encoded based on the specified codepage, and code page 864 cannot represent the standard percent symbol "%". Excel itself can handle it because they have their own implementation of codepages, but other implementations are not necessarily correct (many iconv implementations make the same mistake).

Keep in mind that Unicode only emerged in the 1990s and Excel predates unicode by about a decade.

alister2• 12 years ago

Lots of nice juicy history and interesting detail, but someone who doesn't understand Unicode at all should probably start with this classic article first:

http://www.joelonsoftware.com/articles/Unicode.html (The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets)

and then return to read the featured article.

rspeer• 12 years ago

I'm glad, however, that there is a more modern description. Joel's article dates from a time (2000) when UCS-2 sounded like a good idea.

I'll observe that this article is very C-centric. If Python is how you think about things, I recommend the Python Unicode HOWTO, which of course has two different relevant versions at the moment:

For Python 2: https://docs.python.org/2.7/howto/unicode.html

For Python 3: https://docs.python.org/3/howto/unicode.html

penguindev• 12 years ago

Talk about the tower of babel. This article, although totally excellent, didn't even mention unicode normalization problems. So basically, once everyone starts talking unicode, then we can start trying to figure out what is _meant_. [And not click on some phishing string that looks exactly like some legit string]

moreentropy• 12 years ago

Great article, thanks!

If you're bored or not feeling modern today, read http://en.wikipedia.org/wiki/EBCDIC

For practical Python advice (I'm sure this was on hacker news) http://lucumr.pocoo.org/2013/7/2/the-updated-guide-to-unicod... is a great read.

flohofwoe• 12 years ago

For our multi-platform game projects we have settled with UTF-8, UTF-16 and UTF-32 using the Unicode/LLVM standalone source code to convert between them.

We no longer mess around with code pages, or old-school multibyte encodings like Shift-JIS, and we also don't compile Windows executables in "UNICODE mode", instead we keep all strings as UTF-8, and convert from and to UTF-16 (on Windows) or UTF-32 (on UNIX-like operating systems). Conversion to and from UTF-32 is hardly necessary though, since outside Windows, everything seems to use UTF-8 anyway.

Instead of using OS functions like MultiByteToWideChar() or the iconv library, we have integrated the LLVM/Unicode standalone UTF conversion functions: http://llvm.org/docs/doxygen/html/ConvertUTF_8h_source.html, although with C++11 these conversions are now builtin.

A few other notable points: - properly handling IME input for Asian languages can be tricky (for fullscreen 3D games)

- Arabic text rendering (not because of right-to-left, but because the character appearance changes depending on whether a character is at the start or end of a word, and there is nearly no sample code around which demonstrates this behaviour (and the one we found had all Arabic comments)

- some Asian languages require incredibly huge font textures (most 3D-game text renderers are font-texture based as far as I'm aware of)

[edit: removed redundant link]

lyndonh• 12 years ago

Oh good, another blog post on text coding. We don't have enough of those.

TorKlingberg• 12 years ago

A small addition: Some early/simple Japanese systems actually used single byte encodings. They could only fit the katakana characters, so everything had to be written phonetically. It is not very easy to read but works acceptably for short strings. The characters were squished horizontally to take the same space as English letters: https://en.wikipedia.org/wiki/Half-width_kana

You can still encounter these in printed receipts from old POS systems. The half-width katakana still exist as separate codepoints in Unicode, and are quite popular in emoji and such.

Character Encodings For Modern Programmers

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