Implement missing encodings

[lifthrasiir]

This is a master list for important missing encodings. What is considered "important" is a delicate question, but for now I have the following list:

---

WHATWG multibyte encodings

• gbk
• gb18030
• hz-gb-2312
• big5
• iso-2022-jp
• utf-16be
• utf-16le

Non-WHATWG multibyte encodings of the special interest

• JIS X 0213 encodings: euc-jis-2004, iso-2022-jp-2004, shift-jis-2004
• Other encodings based on Shift_JIS (WHATWG's shift_jis is actually windows-31j)
• cesu-8, required for compatibility

Required for completeness

• iso-8859-1 (compare with windows-1252)
• euc-kr (compare with windows-949)
• euc-jp with and without JIS X 0212 compatibility (WHATWG's euc-jp is asymmetric: it encodes without 0212 and decodes with 0212)
• utf-32 and friends
• utf-7?

[lifthrasiir]

As of b5bdc62 all WHATWG encodings have been implemented. Not all encodings are fully verified though.

[zeld]

Do you have any interest in supporting EBCDIC encodings, maybe behind a feature since they are not the most commonly used? I know that Java provides a built-in support for a limited set, iconv and icu offer more extended support.
If so, I could provide help, for example by providing tables with similar syntax as https://encoding.spec.whatwg.org/index-iso-8859-15.txt

[ssokolow]

Would you be willing to consider supporting IBM code page 437? (The original DOS/IBM PC codepage)

So far, the only Rust support I've been able to find is a read-only crate named cp437 which doesn't inspire confidence. (The heading correctly says "cp437", but then it's typo'd as "cp537" in the very first non-heading line of the README and there's no unit test badge.)

I ask because I have a Python script for generating batch file menus for DOSBox and my retro PC (which means I need to encode box-drawing characters to cp437) and it'd be nice if I could port it to Rust to get more compile-time correctness enforcement and easier distribution to others.