wimlib

Wimlib_iterate_dir_tree() does calculate the SHA-1 for all files the are not yet written to the WIM file.
This is very slow, in case I only want to know if some files or folders exists inside an modified image.

Could you add a flag to skip hashing files?

Hmm, I don't remember why I made wimlib_iterate_dir_tree() hash unhashed files in the first place. It was done by this commit. I'm tempted to just revert that commit, which would make wimlib_iterate_dir_tree() do what you want. (Unhashed files would have all zeroes for their hash.)

This has been fixed on the master branch.