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Adds EXPLODE, UNSHRINK, and UNREDUCE support to BrowserFS's ZipFS.

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BrowserFS ZipFS Extras v1.0.1

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Note: Requires BrowserFS v1.1 and up!

Adds the following decompression algorithms to BrowserFS, which were used in older versions of PKZip:

  • EXPLODE and UNSHRINK (ported from Info-Zip's GPL2'd code)
  • UNREDUCE (ported from this GPL2 code)

Although BrowserFS is licensed under the MIT license, this add-on library is based on GPL2 code and is provided under the GPL2 license.



Simply include browserfs.js and browserfs-zipfs-extras.js on the same page, and BrowserFS will know how to decompress these extra algorithms. Make sure you include browserfs.js first.


Add both browserfs and browserfs-zipfs-extras as dependencies of your project. Then, simply require browserfs-zipfs-extras before you begin using browserfs.

const BrowserFS = require('browserfs');
// Now you can use BrowserFS.


Requires a reasonably recent version of Node. Run:

$ npm install

Running Tests

NOTE: You must have Git LFS installed and use it to clone the repository. We use Git LFS to manage our test fixtures, which are a bunch of zip files.

$ npm test

Porting Comments

We emulate pointers and pointer arithmetic with the Ptr class, which takes an array and an offset into the array. extract.ts and inflate.ts extensively use pointers into Huffman tables as well as pointer arithmetic to iterate through table values!

To reduce object allocations, most Ptr manipulations edit the value of an existing Ptr rather than create a new one. As a result, developers maintaining this project must be cognizant of Ptr aliasing; if two places contain the same Ptr object, then manipulating one will change the other!


Adds EXPLODE, UNSHRINK, and UNREDUCE support to BrowserFS's ZipFS.