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{- git-annex utility functions
-}
module Utility (
withFileLocked,
hGetContentsStrict,
parentDir
) 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. -}
withFileLocked file mode action = do
-- TODO: find a way to use bracket here
handle <- openFile file mode
lockfd <- handleToFd handle -- closes handle
waitToSetLock lockfd (lockType mode, AbsoluteSeek, 0, 0)
handle' <- fdToHandle lockfd
ret <- action handle'
hClose handle'
return ret
where
lockType ReadMode = ReadLock
lockType _ = WriteLock
{- A version of hgetContents that is not lazy. Ensures file is
- all read before it gets closed. -}
hGetContentsStrict h = hGetContents h >>= \s -> length s `seq` return s
{- Returns the parent directory of a path. Parent of / is "" -}
parentDir :: String -> String
parentDir dir =
if length dirs > 0
then absolute ++ (join "/" $ take ((length dirs) - 1) dirs)
else ""
where
dirs = filter (\x -> length x > 0) $ split "/" dir
absolute = if ((dir !! 0) == '/') then "/" else ""
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