http://bugs.winehq.org/show_bug.cgi?id=58155
Brendan Shanks bshanks@codeweavers.com changed:
What |Removed |Added ---------------------------------------------------------------------------- CC| |bshanks@codeweavers.com
--- Comment #3 from Brendan Shanks bshanks@codeweavers.com --- This would be a good improvement to have, but it's unfortunately not straightforward to implement. Windows also has copy-on-write support in the ReFS file system, and there are APIs to use it (see https://learn.microsoft.com/en-us/windows-server/storage/refs/block-cloning) which can clone a specified number of bytes in one file to another existing file. (Linux also has similar reflink APIs).
macOS only has clonefile(2) which copies an entire file to a new filename, and no "specific bytes" or even "preexisting file" API. This is not a good match with the Windows CopyFile() APIs (and the fairly new NT kernel syscall implementing it), which work by first creating the new file, setting attributes, and then copying the bytes in.
I filed a feedback with Apple 2 years ago asking for a system call that can clone parts of files into existing files, without that I don't think this could ever be implemented in upstream Wine. (It might be possible in a downstream like CrossOver though).