X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=System%2FIO.hs;h=0179d8df5e19c531593e35cb4be1e45c1a14b2f3;hb=4b26136ab82fb1ff12e49477c4833a9586d368c5;hp=5fd8ac50d864cba55d7856e3c2c57618ad54090b;hpb=b210a9e5938f1829c293c8685b285a830051708c;p=haskell-directory.git

diff --git a/System/IO.hs b/System/IO.hs
index 5fd8ac5..0179d8d 100644
--- a/System/IO.hs
+++ b/System/IO.hs
@@ -36,6 +36,7 @@ module System.IO (
 
     -- ** Opening files
 
+    withFile,
     openFile,		       -- :: FilePath -> IOMode -> IO Handle
     IOMode(ReadMode,WriteMode,AppendMode,ReadWriteMode),
 
@@ -144,18 +145,17 @@ module System.IO (
 
     -- * Binary input and output
 
+    withBinaryFile,
     openBinaryFile,	       -- :: FilePath -> IOMode -> IO Handle
     hSetBinaryMode,	       -- :: Handle -> Bool -> IO ()
-#if !defined(__NHC__)
     hPutBuf,		       -- :: Handle -> Ptr a -> Int -> IO ()
     hGetBuf,		       -- :: Handle -> Ptr a -> Int -> IO Int
-#endif
 #if !defined(__NHC__) && !defined(__HUGS__)
     hPutBufNonBlocking,	       -- :: Handle -> Ptr a -> Int -> IO Int
     hGetBufNonBlocking,	       -- :: Handle -> Ptr a -> Int -> IO Int
 #endif
 
-    -- * Temporary files
+    -- * Temporary files (not portable: GHC only)
 
 #ifdef __GLASGOW_HASKELL__
     openTempFile,
@@ -179,6 +179,7 @@ import Hugs.IO
 import Hugs.IOExts
 import Hugs.IORef
 import Hugs.Prelude	( throw, Exception(NonTermination) )
+import Control.Exception ( bracket )
 import System.IO.Unsafe	( unsafeInterleaveIO )
 #endif
 
@@ -214,11 +215,13 @@ import IO
   , hIsOpen, hIsClosed        -- :: Handle -> IO Bool
   , hIsReadable, hIsWritable  -- :: Handle -> IO Bool
   , hIsSeekable               -- :: Handle -> IO Bool
+  , bracket
 
   , IO ()
   , FilePath                  -- :: String
   )
-import NHC.IOExtras (fixIO)
+import NHC.IOExtras (fixIO, hPutBuf, hGetBuf)
+import NHC.FFI (Ptr)
 #endif
 
 -- -----------------------------------------------------------------------------
@@ -294,12 +297,8 @@ readFile name	=  openFile name ReadMode >>= hGetContents
 
 -- | The computation 'writeFile' @file str@ function writes the string @str@,
 -- to the file @file@.
-
-writeFile       :: FilePath -> String -> IO ()
-writeFile name str = do
-    hdl <- openFile name WriteMode
-    hPutStr hdl str
-    hClose hdl
+writeFile :: FilePath -> String -> IO ()
+writeFile f txt = withFile f WriteMode (\ hdl -> hPutStr hdl txt)
 
 -- | The computation 'appendFile' @file str@ function appends the string @str@,
 -- to the file @file@.
@@ -311,10 +310,7 @@ writeFile name str = do
 -- > main = appendFile "squares" (show [(x,x*x) | x <- [0,0.1..2]])
 
 appendFile      :: FilePath -> String -> IO ()
-appendFile name str = do
-    hdl <- openFile name AppendMode
-    hPutStr hdl str
-    hClose hdl
+appendFile f txt = withFile f AppendMode (\ hdl -> hPutStr hdl txt)
 
 -- | The 'readLn' function combines 'getLine' and 'readIO'.
 
@@ -367,6 +363,20 @@ hPrint		:: Show a => Handle -> a -> IO ()
 hPrint hdl 	=  hPutStrLn hdl . show
 #endif /* !__NHC__ */
 
+-- | @'withFile' name mode act@ opens a file using 'openFile' and passes
+-- the resulting handle to the computation @act@.  The handle will be
+-- closed on exit from 'withFile', whether by normal termination or by
+-- raising an exception.
+withFile :: FilePath -> IOMode -> (Handle -> IO r) -> IO r
+withFile name mode = bracket (openFile name mode) hClose
+
+-- | @'withBinaryFile' name mode act@ opens a file using 'openBinaryFile'
+-- and passes the resulting handle to the computation @act@.  The handle
+-- will be closed on exit from 'withBinaryFile', whether by normal
+-- termination or by raising an exception.
+withBinaryFile :: FilePath -> IOMode -> (Handle -> IO r) -> IO r
+withBinaryFile name mode = bracket (openBinaryFile name mode) hClose
+
 -- ---------------------------------------------------------------------------
 -- fixIO
 
@@ -408,3 +418,24 @@ hSetBinaryMode _ _ = return ()
 -- It follows that an attempt to write to a file (using 'writeFile', for
 -- example) that was earlier opened by 'readFile' will usually result in
 -- failure with 'System.IO.Error.isAlreadyInUseError'.
+
+-- -----------------------------------------------------------------------------
+-- Utils
+
+#ifdef __GLASGOW_HASKELL__
+-- Copied here to avoid recursive dependency with Control.Exception
+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 =
+  block (do
+    a <- before 
+    r <- catchException
+	   (unblock (thing a))
+	   (\e -> do { after a; throw e })
+    after a
+    return r
+ )
+#endif