{-# LANGUAGE CPP #-}
-- | Compatibility layer for the @unix@ package to provide a @fileSetCaching@ function.
--
-- @unix >= 2.8.7@ defines a @fileSetCaching@ function, but @unix < 2.8.7@ does not. This module defines the function for @unix@ versions @< 2.8.7@. The implementation is adapted from https://github.com/haskell/unix/blob/v2.8.8.0/System/Posix/Fcntl.hsc#L116-L182.
--
-- NOTE: in the future if we no longer support @unix@ versions @< 2.8.7@, then this module can be removed.
module System.FS.BlockIO.Internal.Fcntl (fileSetCaching) where

#if MIN_VERSION_unix(2,8,7)

import System.Posix.Fcntl (fileSetCaching)

#else

#include <fcntl.h>

import           Foreign.C (throwErrnoIfMinus1_)
import           System.Posix.Internals
import           System.Posix.Types (Fd (Fd))

-- | For simplification, we considered that MacOS HAS_F_NOCACHE and !HAS_O_DIRECT
fileSetCaching :: Fd -> Bool -> IO ()
fileSetCaching (Fd fd) val = do
    throwErrnoIfMinus1_ "fileSetCaching" (c_fcntl_write fd #{const F_NOCACHE} (if val then 0 else 1))
#endif