[Libguestfs] [libnbd PATCH] RFC: Add bindings for Rust language

[Martin Kletzander]

On Mon, Jul 08, 2019 at 09:58:20AM +0100, Richard W.M. Jones wrote:
>The patch seems OK in general.
>

The libnbd-sys part is actually complete.  Well, except the build script, but
that one is not completely necessary.  And the documentation.

The wrappers are missing quite a few things to be usable, but it should not be
*that* difficult once someone wants to play with it.

What bothers me a lot is the way I am composing some of the strings.  The only
way why I shamelessly sent this was that the code runs once to generate the file
and it is not part of the resulting product =)

>On Sun, Jul 07, 2019 at 11:39:29PM +0200, Martin Kletzander wrote:
>> The way the code is generated is also not nice, I wish there was
>> more code actually written in some files and not generated by the
>> generator (as much hard-coded static strings as possible), maybe
>> similarly to the states.c, I don't know.
>
>Can you expand on what you mean by this?
>

For example the `impl` blocks can be combined from different modules/files, so
the implementations that are just constant (not generated dynamically, just
static strings printed out) can be in a separate file instead of being written
every time by the generator.

Maybe some substrings could be identified to be common and then copied from a
file instead of duplicating the data.  But this is not needed.

>> Also up for discussion is whether the libnbd crate should be
>> separate since the higher-level functionality it should provide will
>> not be tightly coupled with libnbd itself and the releases
>> (especially the numbers) do not need to happen in sync.
>
>I also didn't understand what this means.
>
>It's a matter of personal preference but you can use multi-line string
>constants in OCaml which can be unlimited in length, so this:
>
>> +  pr "#[allow(unused_imports)]\n";
>> +  pr "use std::os::raw::{c_char, c_int, c_uint, c_void};\n";
>> +  pr "use std::os::unix::io::RawFd;\n";
>> +  pr "use std::ffi::CStr;\n";
>> +  pr "use libnbd_sys::*;\n";
>> +  pr "use libc;\n";
>> +  pr "\n";
>(etc)
>
>can be written as:
>
>  pr "\
>#[allow(unused_imports)]
>use std::os::raw::{c_char, c_int, c_uint, c_void};
>use std::os::unix::io::RawFd;
>[...]
>";

This makes it much nicer, I noticed it in the generator, but I have not spent
any time figuring out why my editor complained about it.  But I wasted a lot of
time on missing/extra semicolons, so it could've been something silly like that.

I'll spend some time one it (that is if I find some spare free time in near
future).

>
>These are still C-like printf-like strings so you still need to escape
>%, " and \.
>
>Rich.
>
>-- 
>Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
>Read my programming and virtualization blog: http://rwmj.wordpress.com
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