correct the documentation for newForeignPtr

[haskell-directory.git] / Foreign / ForeignPtr.hs

diff --git a/Foreign/ForeignPtr.hs b/Foreign/ForeignPtr.hs
index af39a61..21485db 100644 (file)
--- a/Foreign/ForeignPtr.hs
+++ b/Foreign/ForeignPtr.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -fno-implicit-prelude #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Foreign.ForeignPtr
@@ -20,14 +20,29 @@ module Foreign.ForeignPtr
        -- * Finalised data pointers
          ForeignPtr
        , FinalizerPtr
+#if defined(__HUGS__) || defined(__GLASGOW_HASKELL__)
+       , FinalizerEnvPtr
+#endif
+       -- ** Basic operations
         , newForeignPtr
         , newForeignPtr_
         , addForeignPtrFinalizer
+#if defined(__HUGS__) || defined(__GLASGOW_HASKELL__)
+       , newForeignPtrEnv
+       , addForeignPtrFinalizerEnv
+#endif
        , withForeignPtr
+
+#ifdef __GLASGOW_HASKELL__
+       , finalizeForeignPtr
+#endif
+
+       -- ** Low-level operations
        , unsafeForeignPtrToPtr
        , touchForeignPtr
        , castForeignPtr
 
+       -- ** Allocating managed memory
        , mallocForeignPtr
        , mallocForeignPtrBytes
        , mallocForeignPtrArray
@@ -71,10 +86,6 @@ import GHC.ForeignPtr
 
 #if !defined(__NHC__) && !defined(__GLASGOW_HASKELL__)
 import Foreign.Marshal.Alloc   ( malloc, mallocBytes, finalizerFree )
-import Data.Typeable
-
-#include "Typeable.h"
-INSTANCE_TYPEABLE1(ForeignPtr,foreignPtrTc,"ForeignPtr")
 
 instance Eq (ForeignPtr a) where 
     p == q  =  unsafeForeignPtrToPtr p == unsafeForeignPtrToPtr q
@@ -88,17 +99,18 @@ instance Show (ForeignPtr a) where
 
 
 #ifndef __NHC__
-newForeignPtr :: Ptr a -> FinalizerPtr a -> IO (ForeignPtr a)
+newForeignPtr :: FinalizerPtr a -> Ptr a -> IO (ForeignPtr a)
 -- ^Turns a plain memory reference into a foreign pointer, and
 -- associates a finaliser 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
+-- manager.  Indeed, there is no guarantee that the finalizer is executed at
+-- all; a program may exit with finalizers outstanding.  (This is true
+-- of GHC, other implementations may give stronger guarantees).
+newForeignPtr finalizer p
   = do fObj <- newForeignPtr_ p
-       addForeignPtrFinalizer fObj finalizer
+       addForeignPtrFinalizer finalizer fObj
        return fObj
 
 withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
@@ -111,7 +123,7 @@ withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
 -- 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
+-- 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
@@ -127,23 +139,62 @@ withForeignPtr fo io
        return r
 #endif /* ! __NHC__ */
 
+#if defined(__HUGS__) || defined(__GLASGOW_HASKELL__)
+-- | 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'.
+newForeignPtrEnv ::
+    FinalizerEnvPtr env a -> Ptr env -> Ptr a -> IO (ForeignPtr a)
+newForeignPtrEnv finalizer env p
+  = do fObj <- newForeignPtr_ p
+       addForeignPtrFinalizerEnv finalizer env fObj
+       return fObj
+#endif /* __HUGS__ */
+
+#ifdef __GLASGOW_HASKELL__
+type FinalizerEnvPtr env a = FunPtr (Ptr env -> Ptr a -> IO ())
+
+-- | like 'addForeignPtrFinalizerEnv' but allows the finalizer to be
+-- passed an additional environment parameter to be passed to the
+-- finalizer.  The environment passed to the finalizer is fixed by the
+-- second argument to 'addForeignPtrFinalizerEnv'
+addForeignPtrFinalizerEnv ::
+  FinalizerEnvPtr env a -> Ptr env -> ForeignPtr a -> IO ()
+addForeignPtrFinalizerEnv finalizer env fptr = 
+  addForeignPtrConcFinalizer fptr 
+       (mkFinalizerEnv finalizer env (unsafeForeignPtrToPtr fptr))
+
+foreign import ccall "dynamic" 
+  mkFinalizerEnv :: FinalizerEnvPtr env a -> Ptr env -> Ptr a -> IO ()
+#endif
+
+
 #ifndef __GLASGOW_HASKELL__
 mallocForeignPtr :: Storable a => IO (ForeignPtr a)
 mallocForeignPtr = do
   r <- malloc
-  newForeignPtr r finalizerFree
+  newForeignPtr finalizerFree r
 
 mallocForeignPtrBytes :: Int -> IO (ForeignPtr a)
 mallocForeignPtrBytes n = do
   r <- mallocBytes n
-  newForeignPtr r finalizerFree
-#endif /* __HUGS__ || __NHC__ */
+  newForeignPtr finalizerFree r
+#endif /* !__GLASGOW_HASKELL__ */
 
+-- | This function is similar to 'Foreign.Marshal.Array.mallocArray',
+-- but yields a memory area that has a finalizer attached that releases
+-- the memory area.  As with 'mallocForeignPtr', it is not guaranteed that
+-- the block of memory was allocated by 'Foreign.Marshal.Alloc.malloc'.
 mallocForeignPtrArray :: Storable a => Int -> IO (ForeignPtr a)
 mallocForeignPtrArray  = doMalloc undefined
   where
-    doMalloc            :: Storable a => a -> Int -> IO (ForeignPtr a)
+    doMalloc            :: Storable b => b -> Int -> IO (ForeignPtr b)
     doMalloc dummy size  = mallocForeignPtrBytes (size * sizeOf dummy)
 
+-- | This function is similar to 'Foreign.Marshal.Array.mallocArray0',
+-- but yields a memory area that has a finalizer attached that releases
+-- the memory area.  As with 'mallocForeignPtr', it is not guaranteed that
+-- the block of memory was allocated by 'Foreign.Marshal.Alloc.malloc'.
 mallocForeignPtrArray0      :: Storable a => Int -> IO (ForeignPtr a)
 mallocForeignPtrArray0 size  = mallocForeignPtrArray (size + 1)