Parameterise modifyWith.

System/FilePath/Manip.hs

@@ -1,5 +1,8 @@
+{-# OPTIONS_GHC -fglasgow-exts #-}
+
 module System.FilePath.Manip (
-      renameWith
+      Modifiable(..)
+    , renameWith
     , modifyWith
     , modifyWithBackup
     , modifyInPlace
@@ -9,19 +12,45 @@ import Control.Exception (bracket, bracket_, handle, throwIO)
 import Control.Monad (liftM)
 import Data.Bits ((.&.))
 import System.Directory (removeFile)
-import System.IO (IOMode(..), hClose, openFile)
+import System.IO (Handle, IOMode(..), hClose, hGetContents, hPutStr, openFile)
 import System.Posix.Files (fileMode, getFileStatus, rename, setFileMode)
 import System.Posix.Temp (mkstemp)
+import Data.ByteString.Base (ByteString, LazyByteString)
+import qualified Data.ByteString.Char8 as B
 import qualified Data.ByteString.Lazy.Char8 as L
 
 renameWith :: (FilePath -> FilePath) -> FilePath -> IO ()
 
 renameWith f path = rename path (f path)
 
-modifyWith :: (FilePath -> FilePath -> IO ())
-           -> (L.ByteString -> L.ByteString)
-           -> FilePath
-           -> IO ()
+class Modifiable a where
+    pipeline :: (a -> a) -> Handle -> Handle -> IO ()
+
+instance Modifiable ByteString where
+    pipeline f ih oh = B.hGetContents ih >>= return . f >>= B.hPut oh
+
+instance Modifiable LazyByteString where
+    pipeline f ih oh = L.hGetContents ih >>= return . f >>= L.hPut oh
+
+instance Modifiable String where
+    pipeline f ih oh = hGetContents ih >>= return . f >>= hPutStr oh
+
+modifyInPlace :: Modifiable a => (a -> a) -> FilePath -> IO ()
+
+modifyInPlace = modifyWith (flip rename)
+
+modifyWithBackup :: Modifiable a => (FilePath -> FilePath)
+                 -> (a -> a)
+                 -> FilePath
+                 -> IO ()
+
+modifyWithBackup f = modifyWith backup
+    where backup path tmpPath = renameWith f path >> rename tmpPath path
+
+modifyWith :: Modifiable a => (FilePath -> FilePath -> IO ())
+             -> (a -> a)
+             -> FilePath
+             -> IO ()
 
 modifyWith after transform path =
     bracket (openFile path ReadMode) hClose $ \ih -> do
@@ -30,20 +59,8 @@ modifyWith after transform path =
             nukeTmp = handle (const ignore) (removeFile tmpPath)
         handle (\e -> nukeTmp >> throwIO e) $ do
             bracket_ ignore (hClose oh) $
-                transform `liftM` L.hGetContents ih >>= L.hPut oh
+                pipeline transform ih oh
             handle (const nukeTmp) $ do
                 mode <- fileMode `liftM` getFileStatus path
                 setFileMode tmpPath (mode .&. 0777)
                 after path tmpPath
-
-modifyInPlace :: (L.ByteString -> L.ByteString) -> FilePath -> IO ()
-
-modifyInPlace = modifyWith (flip rename)
-
-modifyWithBackup :: (FilePath -> FilePath)
-                 -> (L.ByteString -> L.ByteString)
-                 -> FilePath
-                 -> IO ()
-
-modifyWithBackup f = modifyWith backup
-    where backup path tmpPath = renameWith f path >> rename tmpPath path