[project @ 2002-05-09 13:16:29 by simonmar]

[ghc-base.git] / Foreign / StablePtr.hs

diff --git a/Foreign/StablePtr.hs b/Foreign/StablePtr.hs
index 48acc57..cc53e9c 100644 (file)
--- a/Foreign/StablePtr.hs
+++ b/Foreign/StablePtr.hs
@@ -3,28 +3,46 @@
 -- |
 -- Module      :  Foreign.StablePtr
 -- Copyright   :  (c) The University of Glasgow 2001
--- License     :  BSD-style (see the file libraries/core/LICENSE)
+-- License     :  BSD-style (see the file libraries/base/LICENSE)
 -- 
 -- Maintainer  :  ffi@haskell.org
 -- Stability   :  provisional
 -- Portability :  portable
 --
--- $Id: StablePtr.hs,v 1.4 2002/04/24 16:31:44 simonmar Exp $
---
--- Stable pointers.
+-- This module is part of the Foreign Function Interface (FFI) and will usually
+-- be imported via the module "Foreign".
 --
 -----------------------------------------------------------------------------
 
+
 module Foreign.StablePtr
-        ( StablePtr,         -- abstract
+        ( -- * Stable references to Haskell values
+         StablePtr,         -- abstract
         , newStablePtr       -- :: a -> IO (StablePtr a)
         , deRefStablePtr     -- :: StablePtr a -> IO a
         , freeStablePtr      -- :: StablePtr a -> IO ()
         , castStablePtrToPtr -- :: StablePtr a -> Ptr ()
         , castPtrToStablePtr -- :: Ptr () -> StablePtr a
+       , -- ** The C-side interface
+
+         -- $cinterface
         ) where
 
 #ifdef __GLASGOW_HASKELL__
 import GHC.Stable
 import GHC.Err
 #endif
+
+
+-- $cinterface
+--
+-- The following definition is available to C programs inter-operating with
+-- Haskell code when including the header @HsFFI.h@.
+--
+-- > typedef void *HsStablePtr;  /* C representation of a StablePtr */
+--
+-- Note that no assumptions may be made about the values representing stable
+-- pointers.  In fact, they need not even be valid memory addresses.  The only
+-- guarantee provided is that if they are passed back to Haskell land, the
+-- function 'deRefStablePtr' will be able to reconstruct the
+-- Haskell value refereed to by the stable pointer.