threading through Cstruct

[mor1]

the Lwt_cstruct API seems incomplete now i try to start using it to write buffers out.

specifically, using this as a standard POSIX app albeit (hopefully) in a mirage compatible way, i want to write a Cstruct.t to a file.

i've used Lwt_unix to get me a file_descr Lwt.t, and i've extracted the file_descr from that so that i can Cstruct.write to it:

lwt fd = Lwt_unix.(openfile filename [O_RDWR; O_CREAT] 0o644) in
let _ = Lwt_cstruct.write fd buf in
fd

...except that i can't do that because i need to return an 'a Lwt.t, not an 'a (in this case, 'a is a file_descr).

but then how do i thread things back up so that i can pass the fd through Cstruct.fold somehow? or, as i suspect, do i need to extend Lwt_cstruct to have a fold method?

[avsm]

Right... the blocking versions do need a blocking fold too. That API could be abstracted a little more through a functor, but it's probably not worth it.