[project @ 2003-01-23 18:06:01 by panne]

Added (not-so-standard ;-) support for pooled memory management.
No GHC-specifics like the use of arenas yet...

diff --git a/Foreign/Marshal/Pool.hs b/Foreign/Marshal/Pool.hs
new file mode 100644 (file)
index 0000000..0aa4caf
--- /dev/null
+++ b/Foreign/Marshal/Pool.hs
@@ -0,0 +1,182 @@
+--------------------------------------------------------------------------------
+-- |
+-- Module      :  Foreign.Marshal.Pool
+-- Copyright   :  (c) Sven Panne 2003
+-- License     :  BSD-style (see the file libraries/base/LICENSE)
+-- 
+-- Maintainer  :  sven_panne@yahoo.com
+-- Stability   :  provisional
+-- Portability :  portable
+--
+-- This module contains support for pooled memory management. Under this scheme,
+-- (re-)allocations belong to a given pool, and everything in a pool is
+-- deallocated when the pool itself is deallocated. This is useful when
+-- 'Foreign.Marshal.Alloc.alloca' with its implicit allocation and deallocation
+-- is not flexible enough, but explicit uses of 'Foreign.Marshal.Alloc.malloc'
+-- and 'free' are too awkward.
+--
+--------------------------------------------------------------------------------
+
+module Foreign.Marshal.Pool (
+   -- * Pool management
+   Pool,
+   newPool,             -- :: IO Pool
+   freePool,            -- :: Pool -> IO ()
+   withPool,            -- :: (Pool -> IO b) -> IO b
+
+   -- * (Re-)Allocation within a pool
+   pooledMalloc,        -- :: Storable a => Pool                 -> IO (Ptr a)
+   pooledMallocBytes,   -- ::               Pool          -> Int -> IO (Ptr a)
+
+   pooledRealloc,       -- :: Storable a => Pool -> Ptr a        -> IO (Ptr a)
+   pooledReallocBytes,  -- ::               Pool -> Ptr a -> Int -> IO (Ptr a)
+
+   pooledMallocArray,   -- :: Storable a => Pool ->          Int -> IO (Ptr a)
+   pooledMallocArray0,  -- :: Storable a => Pool ->          Int -> IO (Ptr a)
+
+   pooledReallocArray,  -- :: Storable a => Pool -> Ptr a -> Int -> IO (Ptr a)
+   pooledReallocArray0, -- :: Storable a => Pool -> Ptr a -> Int -> IO (Ptr a)
+
+   -- * Combined allocation and marshalling
+   pooledNew,           -- :: Storable a => Pool -> a            -> IO (Ptr a)
+   pooledNewArray,      -- :: Storable a => Pool ->      [a]     -> IO (Ptr a)
+   pooledNewArray0      -- :: Storable a => Pool -> a -> [a]     -> IO (Ptr a)
+) where
+
+#if defined(__NHC__)
+import IO                       ( bracket )
+#else
+import Control.Exception        ( bracket )
+#endif
+import Control.Monad            ( liftM )
+import Data.IORef               ( IORef, newIORef, readIORef, modifyIORef )
+import Data.List                ( delete )
+import Foreign.Marshal.Alloc    ( mallocBytes, reallocBytes, free )
+import Foreign.Marshal.Array    ( pokeArray, pokeArray0 )
+import Foreign.Marshal.Error    ( throwIf )
+import Foreign.Ptr              ( Ptr, castPtr )
+import Foreign.Storable         ( Storable(sizeOf, poke) )
+
+--------------------------------------------------------------------------------
+
+-- To avoid non-H98 stuff like existentially quantified data constructors, we
+-- simply use pointers to () below. Not very nice, but...
+
+-- | A memory pool.
+
+newtype Pool = Pool (IORef [Ptr ()])
+
+-- | Allocate a fresh memory pool.
+
+newPool :: IO Pool
+newPool = liftM Pool $ newIORef []
+
+-- | Deallocate a memory pool and everything which has been allocated in the
+-- pool itself.
+
+freePool :: Pool -> IO ()
+freePool (Pool ps) = readIORef ps >>= mapM_ free
+
+-- | Execute an action with a fresh memory pool, which gets automatically
+-- deallocated (including its contents) after the action has finished.
+
+withPool :: (Pool -> IO b) -> IO b
+withPool = bracket newPool freePool
+
+--------------------------------------------------------------------------------
+
+-- | Allocate space for storable type in the given pool. The size of the area
+-- allocated is determined by the 'sizeOf' method from the instance of
+-- 'Storable' for the appropriate type.
+
+pooledMalloc :: Storable a => Pool -> IO (Ptr a)
+pooledMalloc = pm undefined
+  where
+    pm           :: Storable a => a -> Pool -> IO (Ptr a)
+    pm dummy pool = pooledMallocBytes pool (sizeOf dummy)
+
+-- | Allocate the given number of bytes of storage in the pool.
+
+pooledMallocBytes :: Pool -> Int -> IO (Ptr a)
+pooledMallocBytes (Pool pool) size = do
+   ptr <- mallocBytes size
+   modifyIORef pool (ptr:)
+   return (castPtr ptr)
+
+-- | Adjust the storage area for an element in the pool to the given size of
+-- the required type.
+
+pooledRealloc :: Storable a => Pool -> Ptr a -> IO (Ptr a)
+pooledRealloc = pr undefined
+  where
+    pr               :: Storable a => a -> Pool -> Ptr a -> IO (Ptr a)
+    pr dummy pool ptr = pooledReallocBytes pool ptr (sizeOf dummy)
+
+-- | Adjust the storage area for an element in the pool to the given size.
+
+pooledReallocBytes :: Pool -> Ptr a -> Int -> IO (Ptr a)
+pooledReallocBytes (Pool pool) ptr size = do
+   let cPtr = castPtr ptr
+   throwIf (not . (cPtr `elem`)) (const "pointer not in pool") (readIORef pool)
+   newPtr <- reallocBytes cPtr size
+   modifyIORef pool ((newPtr :) . delete cPtr)
+   return (castPtr newPtr)
+
+-- | Allocate storage for the given number of elements of a storable type in the
+-- pool.
+
+pooledMallocArray :: Storable a => Pool -> Int -> IO (Ptr a)
+pooledMallocArray = pma undefined
+  where
+    pma                :: Storable a => a -> Pool -> Int -> IO (Ptr a)
+    pma dummy pool size = pooledMallocBytes pool (size * sizeOf dummy)
+
+-- | Allocate storage for the given number of elements of a storable type in the
+-- pool, but leave room for an extra element to signal the end of the array.
+
+pooledMallocArray0 :: Storable a => Pool -> Int -> IO (Ptr a)
+pooledMallocArray0 pool size =
+   pooledMallocArray pool (size + 1)
+
+-- | Adjust the size of an array in the given pool.
+
+pooledReallocArray :: Storable a => Pool -> Ptr a -> Int -> IO (Ptr a)
+pooledReallocArray = pra undefined
+  where
+    pra                ::  Storable a => a -> Pool -> Ptr a -> Int -> IO (Ptr a)
+    pra dummy pool ptr size  = pooledReallocBytes pool ptr (size * sizeOf dummy)
+
+-- | Adjust the size of an array with an end marker in the given pool.
+
+pooledReallocArray0 :: Storable a => Pool -> Ptr a -> Int -> IO (Ptr a)
+pooledReallocArray0 pool ptr size =
+   pooledReallocArray pool ptr (size + 1)
+
+--------------------------------------------------------------------------------
+
+-- | Allocate storage for a value in the given pool and marshal the value into
+-- this storage.
+
+pooledNew :: Storable a => Pool -> a -> IO (Ptr a)
+pooledNew pool val = do
+   ptr <- pooledMalloc pool
+   poke ptr val
+   return ptr
+
+-- | Allocate consecutive storage for a list of values in the given pool and
+-- marshal these values into it.
+
+pooledNewArray :: Storable a => Pool -> [a] -> IO (Ptr a)
+pooledNewArray pool vals = do
+   ptr <- pooledMallocArray pool (length vals)
+   pokeArray ptr vals
+   return ptr
+
+-- | Allocate consecutive storage for a list of values in the given pool and
+-- marshal these values into it, terminating the end with the given marker.
+
+pooledNewArray0 :: Storable a => Pool -> a -> [a] -> IO (Ptr a)
+pooledNewArray0 pool marker vals = do
+   ptr <- pooledMallocArray0 pool (length vals)
+   pokeArray0 marker ptr vals
+   return ptr