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Created July 16, 2011 14:07
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UTF8 encoder
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README.md

UTF8 encoder

A simple UTF8 encoder.

Raw
annotated.js
function(
a, // the text
b, // String.fromCharCode
c, // placeholder
d, // placeholder
e // placeholder
){
for (c=e=''; d=a.charCodeAt(c++); ) // get the Unicode value of the current character
e += d < 128 ? // U+0000-U+007F
b(d) : // 0xxxxxxx
(d < 2048 ? // U+0080-U+07FF
b(d >> 6 | 192) : // 110xxxxx
b(d >> 12 | 224, d >> 6 & 63 | 128) // U+0800-U+FFFF 1110xxxx 10xxxxxx
) + b(d & 63 | 128); // 10xxxxxx
return e;
}
Raw
index.js
function(a,b,c,d,e){for(c=0,e="";d=a.charCodeAt(c++);)e+=d<128?b(d):(d<2048?b(d>>6|192):b(d>>12|224,d>>6&63|128))+b(d&63|128);return e}
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LICENSE.txt
DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
Version 2, December 2004
Copyright (C) 2011 YOUR_NAME_HERE <YOUR_URL_HERE>
Everyone is permitted to copy and distribute verbatim or modified
copies of this license document, and changing it is allowed as long
as the name is changed.
DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. You just DO WHAT THE FUCK YOU WANT TO.
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package.json
{
"name": "utf8encoder",
"description": "A simple UTF8 encoder.",
"keywords": [
"utf8",
"utf-8",
"encode",
"encoder",
"unicode"
]
}
Raw
test.html
<!DOCTYPE html>
<title>UTF8 encode</title>
<div>Expected value: <b>Normal text</b></div>
<div>Actual value: <b id="ret"></b></div>
<script>
var myFunction = function(a,b,c,d,e){for(c=0,e="";d=a.charCodeAt(c++);)e+=d<128?b(d):(d<2048?b(d>>6|192):b(d>>12|224)+b(d>>6&63|128))+b(d&63|128);return e};
document.getElementById( "ret" ).innerHTML = myFunction('Normal text', String.fromCharCode);
</script>
@atk
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atk commented Jul 16, 2011

this is really amazing! - pity that charCodeAt and String.fromCharCode are such byte hoggers.

@tsaniel
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tsaniel commented Jul 17, 2011

Yes, especially the String.fromCharCode. I'm thinking if we can save 20 bytes in order to put the String.fromCharCode inside...

@tsaniel
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tsaniel commented Jul 17, 2011

It seems that there is a more powerful function...
http://ecmanaut.blogspot.com/2006/07/encoding-decoding-utf8-in-javascript.html

@jed
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jed commented Jul 19, 2011

  • c=0,e="" => c=e=""
  • perhaps this is ripe for some sort of eval? d>>6 could appear 3 times.

@jed
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jed commented Jul 19, 2011

also, can you exploit the fact that String.fromCharCode(a,null) === String.fromCharCode(a) ?

@tsaniel
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tsaniel commented Jul 19, 2011

Thanks for your tips, @jed! I think eval is good, but it seems couldn't save bytes with d>>6.
Anyways, that fact is really awesome. I'm still thinking how to exploit it...

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