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newForeignPtr :: FinalizerPtr a -> Ptr a -> IO (ForeignPtr a)base Foreign.ForeignPtr Turns a plain memory reference into a foreign pointer, and associates a finalizer with the reference. The finalizer will be executed after the last reference to the foreign object is dropped. There is no guarantee of promptness, however the finalizer will be executed before the program exits.
newForeignPtrEnv :: FinalizerEnvPtr env a -> Ptr env -> Ptr a -> IO (ForeignPtr a)base Foreign.ForeignPtr This variant of newForeignPtr adds a finalizer that expects an environment in addition to the finalized pointer. The environment that will be passed to the finalizer is fixed by the second argument to newForeignPtrEnv.
newForeignPtr_ :: Ptr a -> IO (ForeignPtr a)base Foreign.ForeignPtr Turns a plain memory reference into a foreign pointer that may be associated with finalizers by using addForeignPtrFinalizer.
plusForeignPtr :: ForeignPtr a -> Int -> ForeignPtr bbase Foreign.ForeignPtr Advances the given address by the given offset in bytes. The new ForeignPtr shares the finalizer of the original, equivalent from a finalization standpoint to just creating another reference to the original. That is, the finalizer will not be called before the new ForeignPtr is unreachable, nor will it be called an additional time due to this call, and the finalizer will be called with the same address that it would have had this call not happened, *not* the new address.
touchForeignPtr :: ForeignPtr a -> IO ()base Foreign.ForeignPtr This function ensures that the foreign object in question is alive at the given place in the sequence of IO actions. However, this comes with a significant caveat: the contract above does not hold if GHC can demonstrate that the code preceding touchForeignPtr diverges (e.g. by looping infinitely or throwing an exception). For this reason, you are strongly advised to use instead withForeignPtr where possible. Also, note that this function should not be used to express dependencies between finalizers on ForeignPtrs. For example, if the finalizer for a ForeignPtr F1 calls touchForeignPtr on a second ForeignPtr F2, then the only guarantee is that the finalizer for F2 is never started before the finalizer for F1. They might be started together if for example both F1 and F2 are otherwise unreachable, and in that case the scheduler might end up running the finalizer for F2 first. In general, it is not recommended to use finalizers on separate objects with ordering constraints between them. To express the ordering robustly requires explicit synchronisation using MVars between the finalizers, but even then the runtime sometimes runs multiple finalizers sequentially in a single thread (for performance reasons), so synchronisation between finalizers could result in artificial deadlock. Another alternative is to use explicit reference counting.
withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO bbase Foreign.ForeignPtr This is a way to look at the pointer living inside a foreign object. This function takes a function which is applied to that pointer. The resulting IO action is then executed. The foreign object is kept alive at least during the whole action, even if it is not used directly inside. Note that it is not safe to return the pointer from the action and use it after the action completes. All uses of the pointer should be inside the withForeignPtr bracket. The reason for this unsafeness is the same as for unsafeForeignPtrToPtr below: the finalizer may run earlier than expected, because the compiler can only track usage of the ForeignPtr object, not a Ptr object made from it. This function is normally used for marshalling data to or from the object pointed to by the ForeignPtr, using the operations from the Storable class.
addForeignPtrFinalizer :: FinalizerPtr a -> ForeignPtr a -> IO ()base Foreign.ForeignPtr.Safe This function adds a finalizer to the given foreign object. The finalizer will run before all other finalizers for the same object which have already been registered.
addForeignPtrFinalizerEnv :: FinalizerEnvPtr env a -> Ptr env -> ForeignPtr a -> IO ()base Foreign.ForeignPtr.Safe Like addForeignPtrFinalizer but the finalizer is passed an additional environment parameter.
castForeignPtr :: ForeignPtr a -> ForeignPtr bbase Foreign.ForeignPtr.Safe This function casts a ForeignPtr parameterised by one type into another type.
finalizeForeignPtr :: ForeignPtr a -> IO ()base Foreign.ForeignPtr.Safe Causes the finalizers associated with a foreign pointer to be run immediately. The foreign pointer must not be used again after this function is called. If the foreign pointer does not support finalizers, this is a no-op.