[Haskell-cafe] getting data through foreign layer without
donn at avvanta.com
Sun Dec 13 20:31:58 EST 2009
I'm working with a C++ application library, of the sort where
you instantiate a subclass of the library object and it dispatches
your functions on receipt of various events. With multiple OS
threads, by the way.
This works all right so far, with some C++ boilerplate and Haskell
FunPtrs created via the foreign "wrapper" option, but I am not crazy
about marshalling the application data, to get it to the C++ object
and back to my application functions.
So, I'm wondering if the way I'm trying to thread application data
through the C++ layer is reasonably fool-proof - I mean, empirically
it works in a simple test, but are there going to be storage issues,
etc.? Is there a better way to do it?
- my callbacks
AppData -> CPlusObjectPtr -> P0 ... -> IO Pn
- the FunPtr inserted into C++ object
FunPtr (CPlusObjectPtr -> P0 ... -> IO Pn)
... i.e, I apply the AppData parameter first
- I rewrite the C++ object's FunPtrs every time I update the
application data (freeHaskellFunPtr prior values.)
I'm just not sure where AppData lives while it's referenced in a
FunPtr via partial application, if there might be multiple copies, etc.
Donn Cave, donn at avvanta.com
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