Add tests from testsuite/tests/h98

[ghc-base.git] / GHC / IO.hs

diff --git a/GHC/IO.hs b/GHC/IO.hs
index d5272ba..ad98a5e 100644 (file)
--- a/GHC/IO.hs
+++ b/GHC/IO.hs
@@ -1,5 +1,10 @@
+{-# LANGUAGE NoImplicitPrelude
+           , BangPatterns
+           , RankNTypes
+           , MagicHash
+           , UnboxedTuples
+  #-}
 {-# OPTIONS_GHC -funbox-strict-fields #-}
-{-# LANGUAGE NoImplicitPrelude, BangPatterns, RankNTypes #-}
 {-# OPTIONS_HADDOCK hide #-}
 -----------------------------------------------------------------------------
 -- |
@@ -31,7 +36,7 @@ module GHC.IO (
     mask, mask_, uninterruptibleMask, uninterruptibleMask_, 
     MaskingState(..), getMaskingState,
     block, unblock, blocked, unsafeUnmask,
-    onException, finally, evaluate
+    onException, bracket, finally, evaluate
   ) where
 
 import GHC.Base
@@ -337,6 +342,7 @@ getMaskingState  = IO $ \s ->
                              1# -> MaskedUninterruptible
                              _  -> MaskedInterruptible #)
 
+{-# DEPRECATED blocked "use Control.Exception.getMaskingState instead" #-}
 -- | returns True if asynchronous exceptions are blocked in the
 -- current thread.
 blocked :: IO Bool
@@ -426,6 +432,18 @@ uninterruptibleMask io = do
     MaskedInterruptible   -> blockUninterruptible $ io block
     MaskedUninterruptible -> io id
 
+bracket
+        :: IO a         -- ^ computation to run first (\"acquire resource\")
+        -> (a -> IO b)  -- ^ computation to run last (\"release resource\")
+        -> (a -> IO c)  -- ^ computation to run in-between
+        -> IO c         -- returns the value from the in-between computation
+bracket before after thing =
+  mask $ \restore -> do
+    a <- before
+    r <- restore (thing a) `onException` after a
+    _ <- after a
+    return r
+
 finally :: IO a         -- ^ computation to run first
         -> IO b         -- ^ computation to run afterward (even if an exception
                         -- was raised)