zip_add with custom non-seekable zip_source_t

[haide-biz]

Is this possible?

My use case:
I have a large file on disk, this file must be encrypted with a custom encryption and then added to the zip file.
I'm on embedded linux with slow and limited flash storage.
I'd like to encrypt and add to the zip file with streaming to avoid temporary files and reduce I/O.

I already have the streaming encryption working.

• It is not seekable
• Resulting size is known after EOF of input stream, not before.

Can I use this streaming encryption to write the encrypted data to a zip file?

[dillof]

Yes, you can wrap your streaming encryption via zip_source_function() and use this source to add it to the archive. You will need to implement the commands ZIP_SOURCE_OPEN, ZIP_SOURCE_READ, ZIP_SOURCE_CLOSE, ZIP_SOURCE_STAT, ZIP_SOURCE_ERROR, and ZIP_SOURCE_FREE.

For ZIP_SOURCE_STAT, you can simply return 0 if you don't want to provide any information.

Unfortunately we don't have a good example for creating a custom source yet, but by looking at the documentation and source code, you should be able to figure it out. If you have questions, feel free to follow up here.

[haide-biz]

Thank you for the fast (and positive) answer!

I'm currently using libarchive and i'd like to switch to libzip.
But i wanted to be sure that this will work before doing the switch.
I already searched the net, read some documentation and asked AI but didn't find a clear answer if the source can be non-seekable or not.

I'll create a small test project and report back if it is working or when i have problems.