> For the complete documentation index, see [llms.txt](https://mmems.gitbook.io/calepin/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mmems.gitbook.io/calepin/formats-encoding-and-protocols/unicode-transformation-formats-utf-8/utf-8.md).

# UTF-8

* [Byte order mark — Wikipedia](https://en.wikipedia.org/wiki/Byte_order_mark)
* [UTF-8 and Unicode Standards](http://www.utf-8.com/)
* [UTF-8 Everywhere](http://utf8everywhere.org/)
* [RFC 3629 - UTF-8, a transformation format of ISO 10646](https://tools.ietf.org/html/rfc3629)
* [Unicode Consortium](http://www.unicode.org/)
* [Unicode Codepoint Chart](http://inamidst.com/stuff/unidata/) and <http://inamidst.com/stuff/unidata/unidata.sh>
* [A Programmer’s Introduction to Unicode – Nathan Reed’s coding blog](http://reedbeta.com/blog/programmers-intro-to-unicode/)
* [Mechanism and Its Consequences : Validating UTF8 strings with Lookup Tables](http://darkcephas.blogspot.com/2018/10/validating-utf8-strings-with-lookup.html) - [darkcephas/utf8Validity\_lookupTable: Non SIMD optimized utf8 string validator](https://github.com/darkcephas/utf8Validity_lookupTable)

UTF-8 est suffisamment intelligent pour coder les chars < 128 sur 1 byte et donc seulement les chars > 128 sur 2 bytes

* ANSI ( les ASCII < 128 ,plus les codepages > 128 jusqu'a 255)
* Unicode ( UTF-16/UCS-2, little endian , cad 2 bytes sont utilisés pour chaque char)
* Unicode Big Endian ( UTF-16/UCS-2, big endian, idem 2 bytes par char )
* UTF-8 ( 1 byte par char < 128, 2 bytes par char > 128)
* [What Every Programmer Absolutely, Positively Needs to Know About Encodings and Character Sets to Work With Text](http://kunststube.net/encoding/)
* [UTF-8 — Wikipedia](https://en.wikipedia.org/wiki/UTF-8)
* [Unicode — Wikipedia](https://en.wikipedia.org/wiki/Unicode#UTF)
* Why the `FAMILY` emoji has a `.length` of 8 (2 for each emoji and 1 for each zero-width joiner) [Emoji.prototype.length — a tale of characters in Unicode - Contentful](https://www.contentful.com/blog/2016/12/06/unicode-javascript-and-the-emoji-family/)
* <https://github.com/mathiasbynens/utf8.js>

```js
function encodeUTF8(string) {
	var utftext = "";

	for (var n = 0; n < string.length; n++) {

		var c = string.charCodeAt(n);

		if (c < 128) {
			utftext += String.fromCharCode(c);
		}
		else if((c > 127) && (c < 2048)) {
			utftext += String.fromCharCode((c >> 6) | 192);
			utftext += String.fromCharCode((c & 63) | 128);
		}
		else {
			utftext += String.fromCharCode((c >> 12) | 224);
			utftext += String.fromCharCode(((c >> 6) & 63) | 128);
			utftext += String.fromCharCode((c & 63) | 128);
		}

	}

	return utftext;
}
```

### Continuation bytes

Can be used to count code points (unicode chars): skip all bytes start with 10xxxxxx

```cpp
// Count UTF-8 chars:
while (*c) count += ((*(c++) & 0xC0) == 0x80) ? 0 : 1;
```

Are part of non first bytes of multi bytes char.

* [unicode - UTF-8 Continuation bytes - Stack Overflow](https://stackoverflow.com/questions/9356169/utf-8-continuation-bytes/9356203#9356203)


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