Integrating FAudio, a reimplementation of XAudio2

[Henri Verbeet]

On Fri, 19 Oct 2018 at 22:26, Ethan Lee <flibitijibibo at flibitijibibo.com> wrote:
> To test the waters, I added the global custom allocator func and tried
> it out with our existing COM wrapper, and aside from making sure that
> it's absolutely called before any API call, it's kind of nice! The
> commit is in a separate branch for now:
>
> https://github.com/FNA-XNA/FAudio/commit/d36e46bf5609859e5796fed378c3d4b241103457
>
> So that's pretty much what it would look like on the Wine side too; any
> function that initializes any portion of the XAudio/XACT APIs would need
> to set the functions before doing anything else. There's definitely
> redundancy and I probably shouldn't be using static functions in our COM
> wrapper, for example, but it works and manages to fix things in a way
> that allows our COM wrapper to work with the stock FAudio.dll on
> Windows, so that's nice!
>
> This doesn't have to be the official API right away, of course, so I'm
> open to feedback on this.
>
I should note that I'm not all that familiar with the specifics of the
XAudio API, so I may be missing the obvious here, but it's not clear
to me why the allocation callbacks would need to be globals. (Reasons
you don't want them to be globals include e.g. different parts of the
same process loading the library, potentially with different
allocators.)

For what it's worth, the kind of API I had in mind would look roughly like this:

    HRESULT faudio_create(const struct faudio_create_info
*create_info, void **xaudio2)
    {
       ...
    }

    HRESULT XAudio2Create(IXAudio2 **xaudio2, UINT32 flags,
XAUDIO2_PROCESSOR proc)
    {
       struct faudio_create_info create_info;

       create_info.type = FAUDIO_STRUCTURE_TYPE_CREATE_INFO;
       create_info.next = NULL;

       create_info.pfn_malloc = SDL_malloc;
       create_info.pfn_realloc = SDL_realloc;
       create_info.pfn_free = SDL_free;

       create_info.iid = &IID_IXAudio28;
       create_info.flags = flags;
       create_info.proc = proc;

       return faudio_create(&create_info, (void **)xaudio2);
    }

Which (again, unsurprisingly) is fairly similar to the vkd3d API.