[libvirt] [PATCH] Change/create solution and project for Visual Studio and MonoDevelop for C# bindings

[Matthias Bolte]

2010/10/20  <arnaud.champion at devatom.fr>:
> The problem with DllMap, is that it works only under Mono, not under .Net :(

Well, no problem three. You keep the [DllImport("libvirt-0.dll")] in
the code for .Net, so it works for .Net and add a DllMap that tells
Mono that it should use libvirt.so.0 on Linux instead of libvirt-0.dll
etc. I think this is exactly how DllMap is supposed to be used.

Matthias

> --------------------------------------------------
> From: "Matthias Bolte" <matthias.bolte at googlemail.com>
> Sent: Tuesday, October 19, 2010 6:38 PM
> To: <arnaud.champion at devatom.fr>
> Cc: <libvir-list at redhat.com>
> Subject: Re: [libvirt] [PATCH] Change/create solution and project for Visual
> Studio and MonoDevelop for C# bindings
>
>> 2010/10/19  <arnaud.champion at devatom.fr>:
>>>
>>> Hi,
>>>
>>> here are 2 patches for C# libvirt bindings.
>>>
>>> These patches create a new solution/project couple for Visual Studio 2010
>>> with also a sample code and a solution/project couple for MonoDevelop
>>> with a
>>> sample code also.
>>>
>>> The sample code have been tested under .Net/Windows, Mono/Windows and
>>> Mono/Linux. And it works, the sample code consist of the using au
>>> virConnectOpenAuth and callback handling. It connect to a URI (I have
>>> made
>>> my tests with ESX hypervisor only) and list domains in a listbox.
>>>
>>> So, to summarize, code work under linux or windows, the binary library
>>> name
>>> depends of a project directive (a kind of pragma). When the directive
>>> WINDOWS is declared, DllImport will try to find "libvirt-0.dll" (for
>>> windows) otherwise it looks for "libvirt.so.0" (for linux). For now, in
>>> the
>>> same manner, when the directive WINDOWS is declared, we find _strdup in
>>> "msvcrt.dll" otherwise we look in "libc.so.6".
>>
>> This makes the resulting binary platform dependent. I asked a friend
>> about this and he suggested to use Mono's dllmap feature [1]. It
>> allows you to stick with [DllImport("libvirt-0.dll")] in the code for
>> .Net and have Mono use libvirt.so.0 on Linux and libvirt.dylib on OSX.
>> This result in a platform independent binary regarding this issue.
>>
>> [1] http://www.mono-project.com/Config_DllMap
>>
>>> I'm currently trying to remove strdup call by Custom Marshaling but it
>>> seems
>>> that .Net (or Mono anyway) doesn't allow to use custom marshaler with
>>> structure (and we need it for virConnectCredential structure). If anyone
>>> had
>>> an idea...
>>
>> Regarding this issue my friend suggested to stop libvirt from taking
>> ownership of cred.result. We could do that by making
>> virConnectOpenAuth take a new VIR_CONNECT_COPY_CRED_RESULT (or
>> VIR_CONNECT_DONT_FREE_CRED_RESULT or VIR_CONNECT_CONST_CRED_RESULT)
>> flag that lets libvirt internally strdup() cred.result before passing
>> it to the driver. That way the C# bindings could pass a managed string
>> as cred.result and we don't need to Marshal.StringToHGlobalAuto() and
>> strdup in C# at all.
>>
>> Or we could make libvirt take a custom free function to free
>> cred.result instead of free(). That way Marshal.FreeHGlobal could be
>> used or no free function at all and you pass a managed string to it.
>> This would probably require a new version of virConnectOpenAuth and I
>> consider this as too invasive.
>>
>> Another possibility would be to add a public virAlloc to libvirt that
>> C# can use to allocate memory that can be freed using free().
>>
>> Matthias
>
>
>