PrivateFile::basic_mv and PrivateFile::cp load full file content in memory

[Frando]

PrivateFile::attach is called by basic_mv and cp to attach a node to a new location in the directory hierarchy.
Through PrivateNode::update_ancestry it goes to PrivateFile::prepare_key_rotation which contains these lines to reencrypt the file content:

let content = self.get_content(forest, store).await?;
self.header.inumber = utils::get_random_bytes(rng);
self.header.update_bare_name(parent_bare_name);
self.header.reset_ratchet(rng);
let content = Self::prepare_content(&self.header.bare_name, content, forest, store, rng).await?;
self.content.content = content;

This will load the full (decrypted) file content into memory and therefore can easily exhaust available memory for large files and/or constrained devices.

Instead this could use PrivateFile::stream_content and PrivateFile::prepare_content_streaming so that not all of the file content has to be in memory at the same time. Maybe it would need some logic to read with the old key and label and write with the new key and label. Or the file could be cloned maybe.

[matheus23]

Yep, you're right. This code predates the streaming APIs.

Instead this could use PrivateFile::stream_contenty and PrivateFile::prepare_content_streaming

That's the way to do it.

Maybe it would need some logic to read with the old key and label and write with the new key and label. Or the file could be cloned maybe.

For now we should make sure the key changes (and not clone the `PrivateFile). We've thought about adding deduplication in the future though. But that's future.

[matheus23]

Now due to some changes from #306 we can actually implement this in a way that wouldn't require us to re-encrypt at all.

[matheus23]

This was fixed in #319