write_buf/read_buf support ? (needed for FUSE_CAP_SPLICE_READ ?)

[touilleMan]

Hi !

Unlike libfuse, it seems fuser doesn't expose write_buf/read_buf callbacks (only write/read are)

I'm by no mean a Fuse expert, but from what I've seen this write_buf/read_buf stuff is not part of the FUSE protocol but instead something internal to libfuse (as I haven't seen any opcode dedicated to it)

According to libfuse's documentation, write_buf must be defined to enable support of FUSE_CAP_SPLICE_READ.
So what does it means for fuser ?

On top of that, I wonder if this write_buf would allow doing zero-copy when doing the write asynchronously (as currently Filesystem::write takes a data: &[u8] parameter so the data must be copied in an owned buffer first if the write operation has to be done in a separated thread, see for instance )