HTTP supports negative ranges, so you can request the final 64KB and scan it. If you don't find the Central Directory (unlikely unless the zip contains 10k files and/or lots of comments) then you just request another 64KB.
Note that the end-of-central-directory record at the end of the file contains the size and offset of the central directory, so if the central directory is not in the final 64 KiB you already have, you know exactly which range you need to request to get it (i.e. you don't need to keep scanning backwards 64 KiB at a time).
I have been a software developer for ten years, enthusiast for 20 years, and am “the computer guy” to my family and friends. However, when I read through something like this, it really feels that my knowledge of computing is ε away from 0…
Thx for a good read!
Uncompressed ZIP files are a bit of an underappreciated container format.
Fetching individual files from a big ZIP file even works over HTTP when the http server support range requests.
Well, you still have to find the zip header no?
HTTP supports negative ranges, so you can request the final 64KB and scan it. If you don't find the Central Directory (unlikely unless the zip contains 10k files and/or lots of comments) then you just request another 64KB.
Note that the end-of-central-directory record at the end of the file contains the size and offset of the central directory, so if the central directory is not in the final 64 KiB you already have, you know exactly which range you need to request to get it (i.e. you don't need to keep scanning backwards 64 KiB at a time).
I have been a software developer for ten years, enthusiast for 20 years, and am “the computer guy” to my family and friends. However, when I read through something like this, it really feels that my knowledge of computing is ε away from 0…
Wait 'til you find out the shenanigans one can do with RAR files!
https://blog.cmpxchg8b.com/2012/09/fun-with-constrained-prog...