{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE CPP, NoImplicitPrelude #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Foreign.Concurrent
-- Copyright   :  (c) The University of Glasgow 2003
-- License     :  BSD-style (see the file libraries/base/LICENSE)
-- 
-- Maintainer  :  [email protected]
-- Stability   :  provisional
-- Portability :  non-portable (requires concurrency)
--
-- FFI datatypes and operations that use or require concurrency (GHC only).
--
-----------------------------------------------------------------------------

module Foreign.Concurrent
  (
        -- * Concurrency-based 'ForeignPtr' operations

        -- | These functions generalize their namesakes in the portable
        -- "Foreign.ForeignPtr" module by allowing arbitrary 'IO' actions
        -- as finalizers.  These finalizers necessarily run in a separate
        -- thread, cf. /Destructors, Finalizers and Synchronization/,
        -- by Hans Boehm, /POPL/, 2003.

        newForeignPtr,
        addForeignPtrFinalizer,
  ) where

#ifdef __GLASGOW_HASKELL__
import GHC.IO         ( IO )
import GHC.Ptr        ( Ptr )
import GHC.ForeignPtr ( ForeignPtr )
import qualified GHC.ForeignPtr

newForeignPtr :: Ptr a -> IO () -> IO (ForeignPtr a)
-- ^Turns a plain memory reference into a foreign object by associating
-- a finalizer - given by the monadic operation - with the reference.
-- The finalizer will be executed after the last reference to the
-- foreign object is dropped.  There is no guarantee of promptness, and
-- in fact there is no guarantee that the finalizer will eventually
-- run at all.
newForeignPtr = GHC.ForeignPtr.newConcForeignPtr

addForeignPtrFinalizer :: ForeignPtr a -> IO () -> IO ()
-- ^This function adds a finalizer to the given 'ForeignPtr'.
-- The finalizer will run after the last reference to the foreign object
-- is dropped, but /before/ all previously registered finalizers for the
-- same object.
addForeignPtrFinalizer = GHC.ForeignPtr.addForeignPtrConcFinalizer
#endif