[Libguestfs] Libguestfs gobject bindings

[Matthew Booth]

On 01/13/2012 10:58 AM, Daniel P. Berrange wrote:
> On Thu, Jan 12, 2012 at 11:59:22AM +0000, Matthew Booth wrote:
>> I'm currently working on gobject bindings for libguestfs. I haven't
>> got as far as compiling anything yet, but I've attached the C header
>> for initial review.
>> typedef struct _GuestfsPV GuestfsPV;
>> struct _GuestfsPV {
>>    gchar *pv_name;
>>    /* The next field is NOT nul-terminated, be careful when printing it: */
>>    gchar pv_uuid[32];
>
> How about a:
>
>     #define GUESTFS_LVM_UUID_BUFLEN 32
>
> and use that throughout

I don't think this one is massively important, because you can always 
use sizeof pv_uuid as an equivalent constant. As the API is 
automatically generated, these are always going to be consistent.

I'd also make this change in the C header and use it here. Rich?

> Obviously all these methods should have  'guestfs_session_' as a prefix

Whoops :)

>> /* Generated methods */
>> gboolean test0(GuestfsSession *session, const gchar *str, const gchar *optstr, GSList *strlist, gboolean b, gint32 integer, gint64 integer64, const gchar *filein, const gchar *fileout, GByteArray *bufferin, GError **err);
>> gint32 test0rint(GuestfsSession *session, const gchar *val, GError **err);
>> gint32 test0rinterr(GuestfsSession *session, , GError **err);
>> gint64 test0rint64(GuestfsSession *session, const gchar *val, GError **err);
>> gint64 test0rint64err(GuestfsSession *session, , GError **err);
>> gboolean test0rbool(GuestfsSession *session, const gchar *val, GError **err);
>> gboolean test0rboolerr(GuestfsSession *session, , GError **err);
>> gchar *test0rconststring(GuestfsSession *session, const gchar *val, GError **err);
>> gchar *test0rconststringerr(GuestfsSession *session, , GError **err);
>> gchar *test0rconstoptstring(GuestfsSession *session, const gchar *val);

>> gint32 wc_c(GuestfsSession *session, const gchar *path, GError **err);
>> GSList *head(GuestfsSession *session, const gchar *path, GError **err);
>> GSList *head_n(GuestfsSession *session, gint32 nrlines, const gchar *path, GError **err);
>> GSList *tail(GuestfsSession *session, const gchar *path, GError **err);
>> GSList *tail_n(GuestfsSession *session, gint32 nrlines, const gchar *path, GError **err);
>> gchar *df(GuestfsSession *session, , GError **err);
>> gchar *df_h(GuestfsSession *session, , GError **err);
>
> Some missing parameters here&  in a few other cases.

Fixed, thanks.

> For the vast majority of these, or at least, any which take non-trivial
> execution time, I think it would be important to add _async variants,
> following the GIO design pattern. eg
>
>    void guest_session_tune2fs_async(GuestfsSession *session, const gchar *device,
>                                     GuestfsTune2FS *optargs,
>                                     GCancellable *cancellable,
>                                     GAsyncReadyCallback callback,
>                                     gpointer user_data);
>    gboolean guest_session_tune2fs_finish(GAsyncResult *result,
>                                          GError **error);
>
> This is a style that is widely preferred by people writing modern GTK
> applications, since it avoids the need to use threads in GUI apps.

Sounds like a good idea. Can I assume that I can safely add this at a 
later date without taking it into account at this stage? If so, I'll 
come back to this once I have a working binding.

Incidentally, I'm also playing with changes to functions with return or 
take array. I've decided to drop GSList in favour of a NULL-terminated 
array as returned by guestfs. For BufferIn and RBufferOut I've dropped 
the GByteArray in favour of a guint8 * with an additional length parameter.

My concern is around memory handling in the bindings. An RStringList 
function returns a NULL-terminated char **. If I cast that to gchar ** 
and return it as-is, will bindings correctly garbage collect it?

Matt
-- 
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

GPG ID:  D33C3490
GPG FPR: 3733 612D 2D05 5458 8A8A 1600 3441 EA19 D33C 3490