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Zip.js - A JavaScript library to zip and unzip files

gildas-lormeau.github.com

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Re: Zip.js - A JavaScript library to zip and unzip files

#13

Post by gildas »

tantalor wrote: post #10
gildas wrote: post #6

I am the author of the library. Just to be clear about my motivations, I wrote this library for chrome extensions. It's a simple way to export/import large user data.

Can you tell us why you don't rely on built-in compression? I would guess both local storage and HTTP POST automatically compress files... is this not the case?

My need is to extract data (archived web pages) from a WebSQL database (or HTML5 filesytem). So the user can export it to a file. Otherwise, he couldn't export the extension data. All is done on client-side so I cannot use HTTP post.

Re: Zip.js - A JavaScript library to zip and unzip files

#14

Post by jonknee »

pooriaazimi wrote: post #8

Also check out: http://jszip.stuartk.co.uk/ I used it a week ago for a simple project (a kinda secure file system - with PHP and MongoDB for backend). I would encrypt a file on my server (AES) and then send the encrypted data to user's browser. Then I could decrypt the data with JavaScript and used JSZip to make user's browser download the decrypted files.

Why go to all the hassle of encrypting/decrypting and not just use HTTPS?

Re: Zip.js - A JavaScript library to zip and unzip files

#15

Post by gildas »

pooriaazimi wrote: post #8

Also check out: http://jszip.stuartk.co.uk/ I used it a week ago for a simple project (a kinda secure file system - with PHP and MongoDB for backend). I would encrypt a file on my server (AES) and then send the encrypted data to user's browser. Then I could decrypt the data with JavaScript and used JSZip to make user's browser download the decrypted files.

Before writing zip.js, I tried this library. It was really great but id does not scale at all: it means the created zip file is not "streamed" so it can use a lot of RAM when creating large files.

Re: Zip.js - A JavaScript library to zip and unzip files

#16

Post by halter73 »

bradleyland wrote: post #9
udp wrote: post #2

Pretty cool, but the thought of inflate/deflate running in Javascript makes me cringe. How fast is this?

I just tested with a 42 MB text log file under OS X 10.7.2. Using zip 3.0: $ time zip logfile.zip logfile.log adding: logfile.log (deflated 89%) real 0m1.170s user 0m0.947s sys 0m0.030s Resulting file size: 4,551,020 bytes Using Chrome 16.0.912.77: 4.7s - 1st drop 5.5s - 2nd drop 5.2s - 3rd drop 5.1s - 4th drop Average 5.125s (timed using stopwatch) Resulting file size: 4,547,885 bytes Size: Advantage Zip.js by 3,135…

Zip.js only has a .069% size advantage over zip 3.0 given your numbers (4,551,020 bytes & 4,547,885 bytes respectively).

Your calculation of 6.8% better than zip just seemed too impressive.

Re: Zip.js - A JavaScript library to zip and unzip files

#19

Post by pooriaazimi »

jonknee wrote: post #14
pooriaazimi wrote: post #8

Also check out: http://jszip.stuartk.co.uk/ I used it a week ago for a simple project (a kinda secure file system - with PHP and MongoDB for backend). I would encrypt a file on my server (AES) and then send the encrypted data to user's browser. Then I could decrypt the data with JavaScript and used JSZip to make user's browser download the decrypted files.

Why go to all the hassle of encrypting/decrypting and not just use HTTPS?

Because it was an assignment for my 'Information & Communication Security' class and I had to do it without SSL/TLS! And it was a fun little project - I learnt how to use JQuery and worked with PHP, MongoDB and JavaScript. I usually code in Java and ObjC and it was a fun break...

Re: Zip.js - A JavaScript library to zip and unzip files

#20

Post by _urga »

gmac wrote: post #7
_urga wrote: post #5

Anyone know of a Javascript implementation of Snappy? There's a binding for Node, but not a Javascript implementation which would be useful in the browser considering IndexedDB and Websockets support binary data.

No, but I've been using an LZMA library [1] to compress data sent over binary WebSockets. LZMA is nice for streaming data to many clients (i.e. compress once, decompress many times), because although compression time/CPU is high (LZMA > BZIP2 > GZIP), compression ratio is very good (LZMA > BZIP2 > GZIP) and decompression not too bad (BZIP2 > LZMA > GZIP) [2]. [1] http://code.google.com/p/js-lzma/ [2] Disclaimer: I sh…

Thank you, I spotted BZIP2 and LZMA. Looking for compression/decompression cpu cost of X < GZIP < BZIP2 < LZMA where compression ratio is of secondary concern.
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