import GHC.Exts
import System.IO
import System.IO.Unsafe ( unsafePerformIO )
-import Data.IORef ( IORef, newIORef, readIORef, writeIORef )
+import Data.IORef ( IORef, newIORef, readIORef, atomicModifyIORef )
import Data.Maybe ( isJust )
import Data.Char ( ord )
lookupTbl (FastStringTable _ arr#) (I# i#) =
IO $ \ s# -> readArray# arr# i# s#
-updTbl :: IORef FastStringTable -> FastStringTable -> Int -> [FastString] -> IO ()
-updTbl fs_table_var (FastStringTable uid arr#) (I# i#) ls = do
+updTbl :: FastStringTable -> Int -> [FastString] -> IO FastStringTable
+updTbl (FastStringTable uid arr#) (I# i#) ls = do
(IO $ \ s# -> case writeArray# arr# i# ls s# of { s2# -> (# s2#, () #) })
- writeIORef fs_table_var (FastStringTable (uid+1) arr#)
+ return (FastStringTable (uid+1) arr#)
+
+-- | Helper function for various forms of fast string constructors.
+mkFSInternal :: Ptr Word8 -> Int
+ -> (Int -> IO FastString)
+ -> IO FastString
+-- The interesting part is the use of unsafePerformIO to make the
+-- argument to atomicModifyIORef pure. This is safe because any
+-- effect dependencies are enforced by data dependencies.
+-- Furthermore, every result is used and hence there should be no
+-- space leaks.
+mkFSInternal ptr len mk_it = do
+ r <- atomicModifyIORef string_table $
+ \fs_tbl@(FastStringTable uid _) ->
+ let h = hashStr ptr len
+ add_it ls = do
+ fs <- mk_it uid
+ fst' <- updTbl fs_tbl h (fs:ls)
+ fs `seq` fst' `seq` return (fst', fs)
+ in unsafePerformIO $ do
+ lookup_result <- lookupTbl fs_tbl h
+ case lookup_result of
+ [] -> add_it []
+ ls -> do
+ b <- bucket_match ls len ptr
+ case b of
+ Nothing -> add_it ls
+ Just v -> return (fs_tbl, v)
+ r `seq` return r
mkFastString# :: Addr# -> FastString
mkFastString# a# = mkFastStringBytes ptr (ptrStrLength ptr)
where ptr = Ptr a#
mkFastStringBytes :: Ptr Word8 -> Int -> FastString
-mkFastStringBytes ptr len = unsafePerformIO $ do
- ft@(FastStringTable uid _) <- readIORef string_table
- let
- h = hashStr ptr len
- add_it ls = do
- fs <- copyNewFastString uid ptr len
- updTbl string_table ft h (fs:ls)
- {- _trace ("new: " ++ show f_str) $ -}
- return fs
- --
- lookup_result <- lookupTbl ft h
- case lookup_result of
- [] -> add_it []
- ls -> do
- b <- bucket_match ls len ptr
- case b of
- Nothing -> add_it ls
- Just v -> {- _trace ("re-use: "++show v) $ -} return v
+mkFastStringBytes ptr len = inlinePerformIO $ do
+ mkFSInternal ptr len (\uid -> copyNewFastString uid ptr len)
mkZFastStringBytes :: Ptr Word8 -> Int -> FastString
-mkZFastStringBytes ptr len = unsafePerformIO $ do
- ft@(FastStringTable uid _) <- readIORef string_table
- let
- h = hashStr ptr len
- add_it ls = do
- fs <- copyNewZFastString uid ptr len
- updTbl string_table ft h (fs:ls)
- {- _trace ("new: " ++ show f_str) $ -}
- return fs
- --
- lookup_result <- lookupTbl ft h
- case lookup_result of
- [] -> add_it []
- ls -> do
- b <- bucket_match ls len ptr
- case b of
- Nothing -> add_it ls
- Just v -> {- _trace ("re-use: "++show v) $ -} return v
+mkZFastStringBytes ptr len = inlinePerformIO $ do
+ mkFSInternal ptr len (\uid -> copyNewZFastString uid ptr len)
-- | Create a 'FastString' from an existing 'ForeignPtr'; the difference
-- between this and 'mkFastStringBytes' is that we don't have to copy
-- the bytes if the string is new to the table.
mkFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString
mkFastStringForeignPtr ptr fp len = do
- ft@(FastStringTable uid _) <- readIORef string_table
--- _trace ("hashed: "++show (I# h)) $
- let
- h = hashStr ptr len
- add_it ls = do
- fs <- mkNewFastString uid ptr fp len
- updTbl string_table ft h (fs:ls)
- {- _trace ("new: " ++ show f_str) $ -}
- return fs
- --
- lookup_result <- lookupTbl ft h
- case lookup_result of
- [] -> add_it []
- ls -> do
- b <- bucket_match ls len ptr
- case b of
- Nothing -> add_it ls
- Just v -> {- _trace ("re-use: "++show v) $ -} return v
+ mkFSInternal ptr len (\uid -> mkNewFastString uid ptr fp len)
mkZFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString
mkZFastStringForeignPtr ptr fp len = do
- ft@(FastStringTable uid _) <- readIORef string_table
--- _trace ("hashed: "++show (I# h)) $
- let
- h = hashStr ptr len
- add_it ls = do
- fs <- mkNewZFastString uid ptr fp len
- updTbl string_table ft h (fs:ls)
- {- _trace ("new: " ++ show f_str) $ -}
- return fs
- --
- lookup_result <- lookupTbl ft h
- case lookup_result of
- [] -> add_it []
- ls -> do
- b <- bucket_match ls len ptr
- case b of
- Nothing -> add_it ls
- Just v -> {- _trace ("re-use: "++show v) $ -} return v
-
+ mkFSInternal ptr len (\uid -> mkNewZFastString uid ptr fp len)
-- | Creates a UTF-8 encoded 'FastString' from a 'String'
mkFastString :: String -> FastString
ZEncoded -> fs
UTF8Encoded ref ->
inlinePerformIO $ do
- m <- readIORef ref
- case m of
- Just fs -> return fs
- Nothing -> do
- let efs = mkZFastString (zEncodeString (unpackFS fs))
- writeIORef ref (Just efs)
- return efs
+ r <- atomicModifyIORef ref $ \m ->
+ case m of
+ Just fs -> (m, fs)
+ Nothing ->
+ let efs = mkZFastString (zEncodeString (unpackFS fs)) in
+ efs `seq` (Just efs, efs)
+ r `seq` return r
appendFS :: FastString -> FastString -> FastString
appendFS fs1 fs2 = mkFastString (unpackFS fs1 ++ unpackFS fs2)
projects / ghc-hetmet.git / blobdiff