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Utility.hs

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+{- git-annex utility functions
+ -}
+
+module Utility where
+
+import System.IO
+import System.Posix.IO
+import Data.String.Utils
+
+{- Let's just say that Haskell makes reading/writing a file with
+ - file locking excessively difficult. -}
+openLocked file mode = do
+	handle <- openFile file mode
+	lockfd <- handleToFd handle -- closes handle
+	waitToSetLock lockfd (lockType mode, AbsoluteSeek, 0, 0)
+	handle' <- fdToHandle lockfd
+	return handle'
+		where
+			lockType ReadMode = ReadLock
+			lockType _ = WriteLock
+
+{- Returns the parent directory of a path. Parent of / is "" -}
+parentDir :: String -> String
+parentDir dir =
+	if length dirs > 0
+	then "/" ++ (join "/" $ take ((length dirs) - 1) dirs)
+	else ""
+		where
+			dirs = filter (\x -> length x > 0) $ split "/" dir