Encrypting large files using SwiftCrypto

It appears that there is no current API for streaming encryption in SwiftCrypto right now. This means that if I have a large file that I want to encrypt, I think I need to load the entire file into memory, then pass it to AES.GCM.seal().

Is this the right way to approach encrypting a large file? Perhaps if I use a Data with a memory-mapped file? Or alternatively, would there be room for proposing API for streamed encryption?