file-type
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sindresorhus
Add support for zlib
Adding support for zlib compressed files. Currently I've added the magic numbers using "no preset dictionary" as they seem to be the ones used in practice.
I used these as references for the magic numbers: https://en.wikipedia.org/wiki/List_of_file_signatures https://stackoverflow.com/questions/9050260/what-does-a-zlib-header-look-like https://datatracker.ietf.org/doc/html/rfc6713 https://datatracker.ietf.org/doc/html/rfc1950
I did notice a conflict with the magic bytes used for the dmg format. After some investigation I think it's using incorrect detection. E.g. when looking at https://en.wikipedia.org/wiki/List_of_file_signatures it's clear that the format signature is at the end of such files (end–512) which seems to match some of my local dmg files as well. I think this should be resolved in a separate issue.
@dr-peppe Bump :)
Sorry, I kind of forgot this as we implemented the check above as a preprocessing step for our zlib purposes for now, doing that check first before falling back to file-type for other file types. But would be nice to get rid of that and just rely on file-type of course :)
I had some problems creating files for test purposes with these other documented variations, but after looking at the Zlib API in later versions of Node I think it might be possible. I need to look into this.