module Foreign.ForeignPtr
(
-- * Finalised data pointers
- ForeignPtr -- abstract, instance of: Eq, Ord, Show
- , newForeignPtr -- :: Ptr a -> IO () -> IO (ForeignPtr a)
- , addForeignPtrFinalizer -- :: ForeignPtr a -> IO () -> IO ()
- , withForeignPtr -- :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
- , foreignPtrToPtr -- :: ForeignPtr a -> Ptr a
- , touchForeignPtr -- :: ForeignPtr a -> IO ()
- , castForeignPtr -- :: ForeignPtr a -> ForeignPtr b
+ ForeignPtr
+ , newForeignPtr
+ , addForeignPtrFinalizer
+ , withForeignPtr
+ , foreignPtrToPtr
+ , touchForeignPtr
+ , castForeignPtr
#ifndef __NHC__
- , mallocForeignPtr -- :: Storable a => IO (ForeignPtr a)
- , mallocForeignPtrBytes -- :: Int -> IO (ForeignPtr a)
- , mallocForeignPtrArray -- :: Storable a => Int -> IO (ForeignPtr a)
- , mallocForeignPtrArray0 -- :: Storable a => Int -> IO (ForeignPtr a)
+ , mallocForeignPtr
+ , mallocForeignPtrBytes
+ , mallocForeignPtrArray
+ , mallocForeignPtrArray0
#endif
)
where
-#ifndef __NHC__
-import Foreign.Ptr
-import Foreign.Storable
-import Data.Dynamic
-#endif
-
-#ifdef __GLASGOW_HASKELL__
-import GHC.Base
-import GHC.IOBase
-import GHC.Num
-import GHC.Ptr ( Ptr(..) )
-import GHC.Err
-import GHC.Show
-#endif
-
#ifdef __NHC__
import NHC.FFI
( ForeignPtr
)
#endif
+#ifdef __GLASGOW_HASKELL__
+import GHC.ForeignPtr
+#endif
+
#ifdef __HUGS__
import Hugs.ForeignPtr
#endif
#ifndef __NHC__
-#include "Dynamic.h"
-INSTANCE_TYPEABLE1(ForeignPtr,foreignPtrTc,"ForeignPtr")
+import Foreign.Storable ( Storable(sizeOf) )
#endif
#ifdef __GLASGOW_HASKELL__
--- |The type 'ForeignPtr' represents references to objects that are
--- maintained in a foreign language, i.e., that are not part of the
--- data structures usually managed by the Haskell storage manager.
--- The essential difference between 'ForeignPtr's and vanilla memory
--- references of type @Ptr a@ is that the former may be associated
--- with /finalisers/. A finaliser is a routine that is invoked when
--- the Haskell storage manager detects that - within the Haskell heap
--- and stack - there are no more references left that are pointing to
--- the 'ForeignPtr'. Typically, the finaliser will, then, invoke
--- routines in the foreign language that free the resources bound by
--- the foreign object.
---
--- The 'ForeignPtr' is parameterised in the same way as 'Ptr'. The
--- type argument of 'ForeignPtr' should normally be an instance of
--- class 'Storable'.
---
-data ForeignPtr a
- = ForeignPtr ForeignObj#
- | MallocPtr (MutableByteArray# RealWorld)
-
-instance Eq (ForeignPtr a) where
- p == q = foreignPtrToPtr p == foreignPtrToPtr q
-
-instance Ord (ForeignPtr a) where
- compare p q = compare (foreignPtrToPtr p) (foreignPtrToPtr q)
-
-instance Show (ForeignPtr a) where
- showsPrec p f = showsPrec p (foreignPtrToPtr f)
-
-
-newForeignPtr :: Ptr a -> IO () -> IO (ForeignPtr a)
--- ^Turns a plain memory reference into a foreign object
--- by associating a finaliser - given by the monadic operation
--- - with the reference. The finaliser will be executed after
--- the last reference to the foreign object is dropped. Note
--- that there is no guarantee on how soon the finaliser is
--- executed after the last reference was dropped; this depends
--- on the details of the Haskell storage manager. The only
--- guarantee is that the finaliser runs before the program
--- terminates.
-newForeignPtr p finalizer
- = do fObj <- mkForeignPtr p
- addForeignPtrFinalizer fObj finalizer
- return fObj
-
--- | allocates some memory and returns a ForeignPtr to it. The memory
--- will be released automatically when the ForeignPtr is discarded.
---
--- @mallocForeignPtr@ is equivalent to
---
--- > do { p <- malloc; newForeignPtr p free }
---
--- although it may be implemented differently internally. You may not
--- assume that the memory returned by 'mallocForeignPtr' has been
--- allocated with C's @malloc()@.
-
-mallocForeignPtr :: Storable a => IO (ForeignPtr a)
-mallocForeignPtr = doMalloc undefined
- where doMalloc :: Storable a => a -> IO (ForeignPtr a)
- doMalloc a = IO $ \s ->
- case newPinnedByteArray# size s of { (# s, mbarr# #) ->
- (# s, MallocPtr mbarr# #)
- }
- where (I# size) = sizeOf a
-
--- | similar to 'mallocForeignPtr', except that the size of the memory required
--- is given explicitly as a number of bytes.
-mallocForeignPtrBytes :: Int -> IO (ForeignPtr a)
-mallocForeignPtrBytes (I# size) = IO $ \s ->
- case newPinnedByteArray# size s of { (# s, mbarr# #) ->
- (# s, MallocPtr mbarr# #)
- }
-
-addForeignPtrFinalizer :: ForeignPtr a -> IO () -> IO ()
--- ^This function adds another finaliser to the given
--- foreign object. No guarantees are made on the order in
--- which multiple finalisers for a single object are run.
-addForeignPtrFinalizer (ForeignPtr fo) finalizer =
- IO $ \s -> case mkWeak# fo () finalizer s of { (# s1, w #) -> (# s1, () #) }
-addForeignPtrFinalizer (MallocPtr fo) finalizer =
- IO $ \s -> case mkWeak# fo () finalizer s of { (# s1, w #) -> (# s1, () #) }
-
-mkForeignPtr :: Ptr a -> IO (ForeignPtr a) {- not exported -}
-mkForeignPtr (Ptr obj) = IO ( \ s# ->
- case mkForeignObj# obj s# of
- (# s1#, fo# #) -> (# s1#, ForeignPtr fo# #) )
-
-touchForeignPtr :: ForeignPtr a -> IO ()
--- ^This function ensures that the foreign object in
--- question is alive at the given place in the sequence of IO
--- actions. In particular 'withForeignPtr'
--- does a 'touchForeignPtr' after it
--- executes the user action.
---
--- This function can be used to express liveness
--- dependencies between 'ForeignPtr's: for
--- example, if the finalizer for one
--- 'ForeignPtr' touches a second
--- 'ForeignPtr', then it is ensured that the
--- second 'ForeignPtr' will stay alive at
--- least as long as the first. This can be useful when you
--- want to manipulate /interior pointers/ to
--- a foreign structure: you can use
--- 'touchForeignObj' to express the
--- requirement that the exterior pointer must not be finalized
--- until the interior pointer is no longer referenced.
-touchForeignPtr (ForeignPtr fo)
- = IO $ \s -> case touch# fo s of s -> (# s, () #)
-touchForeignPtr (MallocPtr fo)
- = IO $ \s -> case touch# fo s of s -> (# s, () #)
-
-withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
--- ^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 unsafety is the same as for
--- 'foreignPtrToPtr' 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.
-withForeignPtr fo io
- = do r <- io (foreignPtrToPtr fo)
- touchForeignPtr fo
- return r
-
-foreignPtrToPtr :: ForeignPtr a -> Ptr a
--- ^This function extracts the pointer component of a foreign
--- pointer. This is a potentially dangerous operations, as if the
--- argument to 'foreignPtrToPtr' is the last usage
--- occurence of the given foreign pointer, then its finaliser(s) will
--- be run, which potentially invalidates the plain pointer just
--- obtained. Hence, 'touchForeignPtr' must be used
--- wherever it has to be guaranteed that the pointer lives on - i.e.,
--- has another usage occurrence.
---
--- To avoid subtle coding errors, hand written marshalling code
--- should preferably use 'withForeignPtr' rather
--- than combinations of 'foreignPtrToPtr' and
--- 'touchForeignPtr'. However, the later routines
--- are occasionally preferred in tool generated marshalling code.
-foreignPtrToPtr (ForeignPtr fo) = Ptr (foreignObjToAddr# fo)
-foreignPtrToPtr (MallocPtr fo) = Ptr (byteArrayContents# (unsafeCoerce# fo))
-
-castForeignPtr :: ForeignPtr a -> ForeignPtr b
--- ^This function casts a 'ForeignPtr'
--- parameterised by one type into another type.
-castForeignPtr (ForeignPtr a) = ForeignPtr a
-castForeignPtr (MallocPtr a) = MallocPtr a
+import GHC.Base
+import GHC.IOBase
+import GHC.Num
+import GHC.Err ( undefined )
#endif
#ifndef __NHC__
projects / haskell-directory.git / commitdiff