[project @ 2003-06-12 12:55:27 by ross]
[ghc.git] / libraries / base / Foreign / ForeignPtr.hs
1 {-# OPTIONS -fno-implicit-prelude #-}
2 -----------------------------------------------------------------------------
3 -- |
4 -- Module : Foreign.ForeignPtr
5 -- Copyright : (c) The University of Glasgow 2001
6 -- License : BSD-style (see the file libraries/base/LICENSE)
7 --
8 -- Maintainer : ffi@haskell.org
9 -- Stability : provisional
10 -- Portability : portable
11 --
12 -- The 'ForeignPtr' type and operations. This module is part of the
13 -- Foreign Function Interface (FFI) and will usually be imported via
14 -- the "Foreign" module.
15 --
16 -----------------------------------------------------------------------------
17
18 module Foreign.ForeignPtr
19 (
20 -- * Finalised data pointers
21 ForeignPtr
22 , FinalizerPtr
23 , newForeignPtr
24 , newForeignPtr_
25 , addForeignPtrFinalizer
26 , withForeignPtr
27 , unsafeForeignPtrToPtr
28 , touchForeignPtr
29 , castForeignPtr
30
31 , mallocForeignPtr
32 , mallocForeignPtrBytes
33 , mallocForeignPtrArray
34 , mallocForeignPtrArray0
35 )
36 where
37
38 import Foreign.Ptr
39
40 #ifdef __NHC__
41 import NHC.FFI
42 ( ForeignPtr
43 , FinalizerPtr
44 , newForeignPtr
45 , newForeignPtr_
46 , addForeignPtrFinalizer
47 , withForeignPtr
48 , unsafeForeignPtrToPtr
49 , touchForeignPtr
50 , castForeignPtr
51 , Storable(sizeOf)
52 , malloc, mallocBytes, finalizerFree
53 )
54 #endif
55
56 #ifdef __HUGS__
57 import Hugs.ForeignPtr
58 #endif
59
60 #ifndef __NHC__
61 import Foreign.Storable ( Storable(sizeOf) )
62 #endif
63
64 #ifdef __GLASGOW_HASKELL__
65 import GHC.Base
66 import GHC.IOBase
67 import GHC.Num
68 import GHC.Err ( undefined )
69 import GHC.ForeignPtr
70 #endif
71
72 #if !defined(__NHC__) && !defined(__GLASGOW_HASKELL__)
73 import Foreign.Marshal.Alloc ( malloc, mallocBytes, finalizerFree )
74 import Data.Dynamic
75
76 #include "Dynamic.h"
77 INSTANCE_TYPEABLE1(ForeignPtr,foreignPtrTc,"ForeignPtr")
78
79 instance Eq (ForeignPtr a) where
80 p == q = unsafeForeignPtrToPtr p == unsafeForeignPtrToPtr q
81
82 instance Ord (ForeignPtr a) where
83 compare p q = compare (unsafeForeignPtrToPtr p) (unsafeForeignPtrToPtr q)
84
85 instance Show (ForeignPtr a) where
86 showsPrec p f = showsPrec p (unsafeForeignPtrToPtr f)
87 #endif
88
89
90 #ifndef __NHC__
91 newForeignPtr :: Ptr a -> FinalizerPtr a -> IO (ForeignPtr a)
92 -- ^Turns a plain memory reference into a foreign pointer, and
93 -- associates a finaliser with the reference. The finaliser will be executed
94 -- after the last reference to the foreign object is dropped. Note that there
95 -- is no guarantee on how soon the finaliser is executed after the last
96 -- reference was dropped; this depends on the details of the Haskell storage
97 -- manager. The only guarantee is that the finaliser runs before the program
98 -- terminates.
99 newForeignPtr p finalizer
100 = do fObj <- newForeignPtr_ p
101 addForeignPtrFinalizer fObj finalizer
102 return fObj
103
104 withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO b
105 -- ^This is a way to look at the pointer living inside a
106 -- foreign object. This function takes a function which is
107 -- applied to that pointer. The resulting 'IO' action is then
108 -- executed. The foreign object is kept alive at least during
109 -- the whole action, even if it is not used directly
110 -- inside. Note that it is not safe to return the pointer from
111 -- the action and use it after the action completes. All uses
112 -- of the pointer should be inside the
113 -- 'withForeignPtr' bracket. The reason for
114 -- this unsafety is the same as for
115 -- 'unsafeForeignPtrToPtr' below: the finalizer
116 -- may run earlier than expected, because the compiler can only
117 -- track usage of the 'ForeignPtr' object, not
118 -- a 'Ptr' object made from it.
119 --
120 -- This function is normally used for marshalling data to
121 -- or from the object pointed to by the
122 -- 'ForeignPtr', using the operations from the
123 -- 'Storable' class.
124 withForeignPtr fo io
125 = do r <- io (unsafeForeignPtrToPtr fo)
126 touchForeignPtr fo
127 return r
128 #endif /* ! __NHC__ */
129
130 #ifndef __GLASGOW_HASKELL__
131 mallocForeignPtr :: Storable a => IO (ForeignPtr a)
132 mallocForeignPtr = do
133 r <- malloc
134 newForeignPtr r finalizerFree
135
136 mallocForeignPtrBytes :: Int -> IO (ForeignPtr a)
137 mallocForeignPtrBytes n = do
138 r <- mallocBytes n
139 newForeignPtr r finalizerFree
140 #endif /* __HUGS__ || __NHC__ */
141
142 mallocForeignPtrArray :: Storable a => Int -> IO (ForeignPtr a)
143 mallocForeignPtrArray = doMalloc undefined
144 where
145 doMalloc :: Storable a => a -> Int -> IO (ForeignPtr a)
146 doMalloc dummy size = mallocForeignPtrBytes (size * sizeOf dummy)
147
148 mallocForeignPtrArray0 :: Storable a => Int -> IO (ForeignPtr a)
149 mallocForeignPtrArray0 size = mallocForeignPtrArray (size + 1)