Re: [Libguestfs] [libnbd PATCH 2/2] RFC: generator: Handle shared callbacks in Python

I have a partial patch which fixes this in a slightly different (but overall quite similar) way. The key observations are: (1) OpaqueAndCallbacks is otherwise known as a list of Closures. A closure list in C corresponds to an opaque pointer + several function pointers (as in your patch). (2) But in other languages, Closures capture local state already so don't require the opaque pointer at all. ie. In OCaml you can already write this to capture some local_data in the closure: let my_chunk_cb local_data subbuf count offset stats error = ... in NBD.pread_structured buf count offset (my_chunk_cb local_data) flags Similarly in Python you can use lambda. There's no need for the opaque to be explicit at all in non-C languages. (3) I don't think we actually have to name the opaque pointer. We can just always call it "void *user_data" in C. (There is max one opaque pointer per function). This simplifies things a bit. (4) We can also probably assume that either all non-persistent or all persistent callbacks are required. (Your patch does that already, but mine uses a boolean flag instead of separate case). Will post later. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html