Possible to have fides without known size in FUSE fs?

[Harry Mallon]

Is it possible in FUSE (even in a weird way) to have files in the FUSE fs that require significant processing and which therefore you do not know the file size for until they are copied?

Say I wanted to offer users of the filesystem compressed files to copy but they take a while to create. I would not want to compress the file for a stat call, maybe I could estimate the final size or give the worst case. I would only want to provide real data when a client was reading the file. Any ideas?