bindings-common-0.2.4: Macros and modules to facilitate writing library bindings. Source code Contents Index

Bindings.Utilities

Synopsis

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 a Source

class Storable cb => Callback cb where Source

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 type F cb :: * Source The associated type is the function type as it is used in Haskell. Methods nullCallback :: cb Source nullCallback can be used like Foreign.Ptr.nullFunPtr. makeCallback :: F cb -> IO cb Source 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 values returned by makeCallback after they are no longer going to be used. Most of the time this class method will just use Foreign.Ptr.freeHaskellFunPtr. withCallback :: F cb -> (cb -> IO a) -> IO a Source withCallback just inserts an action between calls to makeCallback and freeCallback. Of course, it can't be used when foreign code will save such action for latter use.

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