{-# LANGUAGE CApiFFI #-}
{-# LANGUAGE CPP     #-}

module Network.DNS.FFI where

import           Control.Concurrent.MVar
import           Foreign.C
import           Foreign.Marshal.Alloc
import           Foreign.Ptr
import           System.IO.Unsafe        (unsafePerformIO)

#if !defined(USE_RES_NQUERY)
# error USE_RES_NQUERY not defined
#endif

{-# INLINE resIsReentrant #-}
-- | Whether the reentrant DNS resolver C API (e.g. @res_nquery(3)@, @res_nsend(3)@) is being used.
--
-- If this this 'False', then as a fall-back
-- @res_query(3)@/@res_send(3)@ are used, protected by a global mutex.
--
-- @since 0.1.1.0
resIsReentrant :: Bool
#if USE_RES_NQUERY
resIsReentrant :: Bool
resIsReentrant = Bool
True
#else
resIsReentrant = False
#endif

#if !defined(SIZEOF_RES_STATE)
# error SIZEOF_RES_STATE not defined
#endif

#if USE_RES_NQUERY && (SIZEOF_RES_STATE <= 0)
# error broken invariant
#endif

{-# INLINE sizeOfResState #-}
sizeOfResState :: CSize
sizeOfResState :: CSize
sizeOfResState = SIZEOF_RES_STATE

data CResState

{-# NOINLINE resolvLock #-}
resolvLock :: MVar ()
resolvLock :: MVar ()
resolvLock = IO (MVar ()) -> MVar ()
forall a. IO a -> a
unsafePerformIO (IO (MVar ()) -> MVar ()) -> IO (MVar ()) -> MVar ()
forall a b. (a -> b) -> a -> b
$ () -> IO (MVar ())
forall a. a -> IO (MVar a)
newMVar ()

withCResState :: (Ptr CResState -> IO a) -> IO a
withCResState :: (Ptr CResState -> IO a) -> IO a
withCResState act :: Ptr CResState -> IO a
act
  | Bool
resIsReentrant = Int -> (Ptr CResState -> IO a) -> IO a
forall a b. Int -> (Ptr a -> IO b) -> IO b
allocaBytes (CSize -> Int
forall a b. (Integral a, Num b) => a -> b
fromIntegral CSize
sizeOfResState) ((Ptr CResState -> IO a) -> IO a)
-> (Ptr CResState -> IO a) -> IO a
forall a b. (a -> b) -> a -> b
$ \ptr :: Ptr CResState
ptr -> do
                         Ptr CResState
_ <- Ptr CResState -> CInt -> CSize -> IO (Ptr CResState)
forall a. Ptr a -> CInt -> CSize -> IO (Ptr a)
c_memset Ptr CResState
ptr 0 CSize
sizeOfResState
                         Ptr CResState -> IO a
act Ptr CResState
ptr
  | Bool
otherwise = MVar () -> (() -> IO a) -> IO a
forall a b. MVar a -> (a -> IO b) -> IO b
withMVar MVar ()
resolvLock ((() -> IO a) -> IO a) -> (() -> IO a) -> IO a
forall a b. (a -> b) -> a -> b
$ \() -> Ptr CResState -> IO a
act Ptr CResState
forall a. Ptr a
nullPtr


-- void *memset(void *s, int c, size_t n);
foreign import capi unsafe "string.h memset" c_memset :: Ptr a -> CInt -> CSize -> IO (Ptr a)

-- int res_query(void *, const char *dname, int class, int type, unsigned char *answer, int anslen);
foreign import capi safe "hs_resolv.h hs_res_query" c_res_query :: Ptr CResState -> CString -> CInt -> CInt -> Ptr CChar -> CInt -> IO CInt

-- int res_send(void *, const unsigned char *msg, int msglen, unsigned char *answer, int anslen);
foreign import capi safe "hs_resolv.h hs_res_send" c_res_send :: Ptr CResState -> Ptr CChar -> CInt -> Ptr CChar -> CInt -> IO CInt

-- int res_opt_set_use_dnssec(void *);
foreign import capi safe "hs_resolv.h res_opt_set_use_dnssec" c_res_opt_set_use_dnssec :: Ptr CResState -> IO CInt

-- int hs_res_mkquery(void *, const char *dname, int class, int type, unsigned char *req, int reqlen0);
foreign import capi safe "hs_resolv.h hs_res_mkquery" c_res_mkquery :: Ptr CResState -> CString -> CInt -> CInt -> Ptr CChar -> CInt -> IO CInt