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{-# OPTIONS_GHC -XNoImplicitPrelude #-}
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-----------------------------------------------------------------------------
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-- Module : Foreign.ForeignPtr
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-- Copyright : (c) The University of Glasgow 2001
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-- License : BSD-style (see the file libraries/base/LICENSE)
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-- Maintainer : ffi@haskell.org
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-- Stability : provisional
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-- Portability : portable
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-- The 'ForeignPtr' type and operations. This module is part of the
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-- Foreign Function Interface (FFI) and will usually be imported via
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-- the "Foreign" module.
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-----------------------------------------------------------------------------
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module Foreign.ForeignPtr
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-- * Finalised data pointers
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#if defined(__HUGS__) || defined(__GLASGOW_HASKELL__)
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-- ** Basic operations
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, addForeignPtrFinalizer
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#if defined(__HUGS__) || defined(__GLASGOW_HASKELL__)
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, addForeignPtrFinalizerEnv
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#ifdef __GLASGOW_HASKELL__
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-- ** Low-level operations
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, unsafeForeignPtrToPtr
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-- ** Allocating managed memory
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, mallocForeignPtrBytes
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, mallocForeignPtrArray
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, mallocForeignPtrArray0
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, addForeignPtrFinalizer
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, unsafeForeignPtrToPtr
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, malloc, mallocBytes, finalizerFree
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import Hugs.ForeignPtr
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import Foreign.Storable ( Storable(sizeOf) )
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#ifdef __GLASGOW_HASKELL__
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import GHC.Err ( undefined )
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#if !defined(__NHC__) && !defined(__GLASGOW_HASKELL__)
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import Foreign.Marshal.Alloc ( malloc, mallocBytes, finalizerFree )
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instance Eq (ForeignPtr a) where
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p == q = unsafeForeignPtrToPtr p == unsafeForeignPtrToPtr q
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instance Ord (ForeignPtr a) where
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compare p q = compare (unsafeForeignPtrToPtr p) (unsafeForeignPtrToPtr q)
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instance Show (ForeignPtr a) where
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showsPrec p f = showsPrec p (unsafeForeignPtrToPtr f)
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newForeignPtr :: FinalizerPtr a -> Ptr a -> IO (ForeignPtr a)
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-- ^Turns a plain memory reference into a foreign pointer, and
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-- associates a finalizer with the reference. The finalizer will be
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-- executed after the last reference to the foreign object is dropped.
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-- There is no guarantee of promptness, however the finalizer will be
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-- executed before the program exits.
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newForeignPtr finalizer p
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= do fObj <- newForeignPtr_ p
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addForeignPtrFinalizer finalizer fObj
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withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
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-- ^This is a way to look at the pointer living inside a
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-- foreign object. This function takes a function which is
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-- applied to that pointer. The resulting 'IO' action is then
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-- executed. The foreign object is kept alive at least during
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-- the whole action, even if it is not used directly
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-- inside. Note that it is not safe to return the pointer from
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-- the action and use it after the action completes. All uses
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-- of the pointer should be inside the
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-- 'withForeignPtr' bracket. The reason for
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-- this unsafeness is the same as for
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-- 'unsafeForeignPtrToPtr' below: the finalizer
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-- may run earlier than expected, because the compiler can only
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-- track usage of the 'ForeignPtr' object, not
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-- a 'Ptr' object made from it.
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-- This function is normally used for marshalling data to
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-- or from the object pointed to by the
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-- 'ForeignPtr', using the operations from the
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= do r <- io (unsafeForeignPtrToPtr fo)
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#endif /* ! __NHC__ */
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#if defined(__HUGS__) || defined(__GLASGOW_HASKELL__)
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-- | This variant of 'newForeignPtr' adds a finalizer that expects an
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-- environment in addition to the finalized pointer. The environment
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-- that will be passed to the finalizer is fixed by the second argument to
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-- 'newForeignPtrEnv'.
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FinalizerEnvPtr env a -> Ptr env -> Ptr a -> IO (ForeignPtr a)
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newForeignPtrEnv finalizer env p
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= do fObj <- newForeignPtr_ p
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addForeignPtrFinalizerEnv finalizer env fObj
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#endif /* __HUGS__ */
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#ifndef __GLASGOW_HASKELL__
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mallocForeignPtr :: Storable a => IO (ForeignPtr a)
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mallocForeignPtr = do
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newForeignPtr finalizerFree r
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mallocForeignPtrBytes :: Int -> IO (ForeignPtr a)
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mallocForeignPtrBytes n = do
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newForeignPtr finalizerFree r
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#endif /* !__GLASGOW_HASKELL__ */
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-- | This function is similar to 'Foreign.Marshal.Array.mallocArray',
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-- but yields a memory area that has a finalizer attached that releases
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-- the memory area. As with 'mallocForeignPtr', it is not guaranteed that
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-- the block of memory was allocated by 'Foreign.Marshal.Alloc.malloc'.
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mallocForeignPtrArray :: Storable a => Int -> IO (ForeignPtr a)
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mallocForeignPtrArray = doMalloc undefined
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doMalloc :: Storable b => b -> Int -> IO (ForeignPtr b)
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doMalloc dummy size = mallocForeignPtrBytes (size * sizeOf dummy)
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-- | This function is similar to 'Foreign.Marshal.Array.mallocArray0',
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-- but yields a memory area that has a finalizer attached that releases
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-- the memory area. As with 'mallocForeignPtr', it is not guaranteed that
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-- the block of memory was allocated by 'Foreign.Marshal.Alloc.malloc'.
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mallocForeignPtrArray0 :: Storable a => Int -> IO (ForeignPtr a)
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mallocForeignPtrArray0 size = mallocForeignPtrArray (size + 1)