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htaccess file. Then load an html or js file via the server and check the headers for "Content-Encoding", if it says gzip or deflate, it is enabled. You need access to your vhost/server config to globally enable compression. You don't need to prepare your files, they're compressed automatically on request.
If the gzip compression is enabled on the web server, that is, not in the application logic, then the browser will uncompress automatically.
Gzip Compression is Enabled by Default.
If you take a file that is 1300 bytes and compress it to 800 bytes, it's still transmitted in that same 1500 byte packet regardless, so you've gained nothing. That being the case, you should restrict the gzip compression to files with a size greater than a single packet, 1400 bytes (1.4KB) is a safe value.
Edit There appears to be a better LZW solution that handles Unicode strings correctly at http://pieroxy.net/blog/pages/lz-string/index.html (Thanks to pieroxy in the comments).
I don't know of any gzip implementations, but the jsolait library (the site seems to have gone away) has functions for LZW compression/decompression. The code is covered under the LGPL.
// LZW-compress a string
function lzw_encode(s) {
var dict = {};
var data = (s + "").split("");
var out = [];
var currChar;
var phrase = data[0];
var code = 256;
for (var i=1; i<data.length; i++) {
currChar=data[i];
if (dict[phrase + currChar] != null) {
phrase += currChar;
}
else {
out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
dict[phrase + currChar] = code;
code++;
phrase=currChar;
}
}
out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
for (var i=0; i<out.length; i++) {
out[i] = String.fromCharCode(out[i]);
}
return out.join("");
}
// Decompress an LZW-encoded string
function lzw_decode(s) {
var dict = {};
var data = (s + "").split("");
var currChar = data[0];
var oldPhrase = currChar;
var out = [currChar];
var code = 256;
var phrase;
for (var i=1; i<data.length; i++) {
var currCode = data[i].charCodeAt(0);
if (currCode < 256) {
phrase = data[i];
}
else {
phrase = dict[currCode] ? dict[currCode] : (oldPhrase + currChar);
}
out.push(phrase);
currChar = phrase.charAt(0);
dict[code] = oldPhrase + currChar;
code++;
oldPhrase = phrase;
}
return out.join("");
}
I had another problem, I did not want to encode data in gzip but to decode gzipped data. I am running javascript code outside of the browser so I need to decode it using pure javascript.
It took me some time but i found that in the JSXGraph library there is a way to read gzipped data.
Here is where I found the library: http://jsxgraph.uni-bayreuth.de/wp/2009/09/29/jsxcompressor-zlib-compressed-javascript-code/ There is even a standalone utility that can do that, JSXCompressor, and the code is LGPL licencied.
Just include the jsxcompressor.js file in your project and then you will be able to read a base 64 encoded gzipped data:
<!doctype html>
</head>
<title>Test gzip decompression page</title>
<script src="jsxcompressor.js"></script>
</head>
<body>
<script>
document.write(JXG.decompress('<?php
echo base64_encode(gzencode("Try not. Do, or do not. There is no try."));
?>'));
</script>
</html>
I understand it is not what you wanted but I still reply here because I suspect it will help some people.
We just released pako https://github.com/nodeca/pako , port of zlib to javascript. I think that's now the fastest js implementation of deflate / inflate / gzip / ungzip. Also, it has democratic MIT licence. Pako supports all zlib options and its results are binary equal.
Example:
var inflate = require('pako/lib/inflate').inflate;
var text = inflate(zipped, {to: 'string'});
I ported an implementation of LZMA from a GWT module into standalone JavaScript. It's called LZMA-JS.
Here are some other compression algorithms implemented in Javascript:
I did not test, but there's a javascript implementation of ZIP, called JSZip:
https://stuk.github.io/jszip/
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