[gmpi] Re: low level API
- From: jeffmcc@xxxxxxxxxx
- To: gmpi@xxxxxxxxxxxxx
- Date: Wed, 02 Feb 2005 10:29:23 +1300
> Also on Mac OS X the C pointer functions are used when
> crossing CFM/PEF and Mach-O boundaries. And maybe later
The convention with a dispatcher is to pass the object
pointer as the first argument...
void dispatcher( void *object_ptr, ....
...so, although that's plain C code, it's also the same
signature as C++ (standard calling convention) where the
'this' pointer is secretly passed as the first argument.
so, a clever plugin can 'cheat' and treat the call as C++.
You get the portability of plain C, but no performance
penalty when talking to a C++ plugin.
The advantage of a dispatcher is you can extend the API by
adding new opcodes, you don't change the binary interface,
makes backward/forward compatibilty very easy.
>
> On 1.2.2005, at 21:26, Ron Kuper wrote:
>
> >>>>
> > Even those things are very fundamental. A dispatcher
> > based API has merits, but might not work. An object API
> > has merits, but is notoriously fugly in C.
> > <<<
> >
> > I would like to see a dispatcher based API (for
> > retaining the requirement of C ABI), but have it
> > immediately drop into a C++ object heirarchy. Not that
> > I want to emulate it necessary, but MFC does this in
> bridging Win32 messaging with a class library.
>
> Also on Mac OS X the C pointer functions are used when
> crossing CFM/PEF and Mach-O boundaries. And maybe later
> will be used again when running up to another new binary
> object model.
>
> PM
>
>
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