    {-# LINE 1 "libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock/Flock.hsc" #-}
    {-# LANGUAGE CPP #-}
    {-# LANGUAGE InterruptibleFFI #-}
    {-# LANGUAGE LambdaCase #-}
    {-# LANGUAGE MultiWayIf #-}
    {-# LANGUAGE NoImplicitPrelude #-}

    -- | File locking via POSIX @flock@.
    module GHC.Internal.IO.Handle.Lock.Flock where

    {-# LINE 15 "libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock/Flock.hsc" #-}

    import GHC.Internal.Data.Bits
    import GHC.Internal.Data.Function
    import GHC.Internal.Foreign.C.Error
    import GHC.Internal.Foreign.C.Types
    import GHC.Internal.Base
    import GHC.Internal.IO.Exception
    import GHC.Internal.IO.FD
    import GHC.Internal.IO.Handle.FD
    import GHC.Internal.IO.Handle.Lock.Common
    import GHC.Internal.IO.Handle.Types (Handle)

    lockImpl :: Handle -> String -> LockMode -> Bool -> IO Bool
    lockImpl :: Handle -> String -> LockMode -> Bool -> IO Bool
    lockImpl Handle
    h String
    ctx LockMode
    mode Bool
    block = do
      FD{fdFD = fd} <- Handle -> IO FD
    handleToFd Handle
    h
      let flags = CInt
    cmode CInt -> CInt -> CInt
    forall a. Bits a => a -> a -> a
    .|. (if Bool
    block then CInt
    0 else CInt
    4)
    {-# LINE 33 "libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock/Flock.hsc" #-}
      fix $ \retry -> c_flock fd flags >>= \case
        0 -> return True
        _ -> getErrno >>= \errno -> if
          | not block
          , errno == eAGAIN || errno == eACCES -> return False
          | errno == eINTR -> retry
          | otherwise -> ioException $ errnoToIOError ctx errno (Just h) Nothing
      where
        cmode :: CInt
    cmode = case LockMode
    mode of
          LockMode
    SharedLock    -> CInt
    1
    {-# LINE 43 "libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock/Flock.hsc" #-}
          ExclusiveLock -> 2
    {-# LINE 44 "libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock/Flock.hsc" #-}

    unlockImpl :: Handle -> IO ()
    unlockImpl :: Handle -> IO ()
    unlockImpl Handle
    h = do
      FD{fdFD = fd} <- Handle -> IO FD
    handleToFd Handle
    h
      throwErrnoIfMinus1_ "flock" $ c_flock fd 8
    {-# LINE 49 "libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock/Flock.hsc" #-}

    foreign import ccall interruptible "flock"
      c_flock :: CInt -> CInt -> IO CInt

    {-# LINE 54 "libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock/Flock.hsc" #-}