Title: New Zipper release
Date: 2007-05-22
Lang: en

I had to debug Mule's build for the upcoming 1.4.1 release a bit, especially the packaging of the JCA distribution. I usually use Zipper to open archives, that's why I wrote it in the first place. It turns out that some file extensions are ambiguous, e.g. a file ending in .rar could either be a rar archive or a Java Resource ARchive which is effectively a zip file. Since the rar packager cannot handle zip files I picked up an idea I had in mind for a long time now: file types should not be determined by their extensions but the way the unix file command does it: by looking for certain patterns inside of a file. I implemented the most simple cases in Zipper now: Zip files begin with

	:::shell
    { 'P', 'K', 0x003, 0x004 }

and rar files begin with

	:::shell
    { 'R', 'a', 'r', '!'}

straight from the beginning of the file. When opening a file Zipper asks all registered Archive subclasses for their magic bytes and compares them to the first four bytes of the file. I think I will extend this mechanism a bit in the future so in the end all supported archives will be determined by a file's content and not by its file extension any more.