{-# LANGUAGE ForeignFunctionInterface #-}

{-| Necessary foreign function calls

...with foreign functions declared in unistd.h

-}

{-

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-}

module Ganeti.Utils.UniStd
  ( fsyncFile
  ) where

import Control.Exception (bracket)
import Foreign.C
import System.Posix.IO
import System.Posix.Types

import Ganeti.BasicTypes

foreign import ccall "fsync" fsync :: CInt -> IO CInt

-- Opens a file and calls fsync(2) on the file descriptor.
--
-- Because of a bug in GHC 7.6.3 (at least), calling 'hIsClosed' on a handle
-- to get the file descriptor leaks memory. Therefore we open a given file
-- just to sync it and close it again.
fsyncFile :: (FromString e) => FilePath -> ResultT e IO ()
fsyncFile path = liftIO
  $ bracket (openFd path ReadOnly Nothing defaultFileFlags) closeFd callfsync
  where
    callfsync (Fd fd) = throwErrnoPathIfMinus1_ "fsyncFile" path $ fsync fd