Bindings.Utilities
- data Storable a => GlobalVariable a
- writeGlobalVariable :: Storable a => GlobalVariable a -> a -> IO ()
- readGlobalVariable :: Storable a => GlobalVariable a -> IO a
- class Storable cb => Callback cb where
- type F cb :: *
- nullCallback :: cb
- makeCallback :: F cb -> IO cb
- freeCallback :: cb -> IO ()
- withCallback :: F cb -> (cb -> IO a) -> IO a
Documentation
data Storable a => GlobalVariable a Source
Haskell FFI imports global variables as pointers. To
ease manipulation of such pointers they are encapsulated
by GlobalVariable so that values can be reached
directly, much like in an Data.IORef.
writeGlobalVariable :: Storable a => GlobalVariable a -> a -> IO ()Source
readGlobalVariable :: Storable a => GlobalVariable a -> IO aSource
class Storable cb => Callback cb whereSource
When libraries provide types for functions those
types are made instances of class Callback. That
class is used to exchange between Haskell functions
and a representation (i.e., a hidden pointer) that
can be used or is provided by foreign code.
Associated Types
The associated type is the function type as it is used in Haskell.
Methods
nullCallback :: cbSource
nullCallback can be used like Foreign.Ptr.nullPtr
or Foreign.Ptr.nullFunPtr.
makeCallback :: F cb -> IO cbSource
makeCallback takes a Haskell function and
gives a representation of it in the form of the
type expected by foreign code.
freeCallback :: cb -> IO ()Source
freeCallback should be called on all members
of a foreign function type after they
are no longer going to be used.
withCallback :: F cb -> (cb -> IO a) -> IO aSource
withCallback just inserts an action between
calls to makeCallback and freeCallback.
Of course, it can't be used when foreign code
will save the function for latter use.