To wrap the ansi C fn void MurmurHash3_x86_32 (const void *key, int len, uint32_t seed, void *out);

Murmur3.hs

{-# LANGUAGE ForeignFunctionInterface #-}

module Data.Dish.Murmur3(x86_32
                          --,x86_128,x64_128
                          ) where
import Foreign.C -- get the C types
import Foreign.Ptr
import Foreign
import qualified Foreign.ForeignPtr.Unsafe as US

foreign import ccall "MurmurHash3_x86_32" c_x86_32 
  ::  Ptr CString -> CInt -> CUInt ->  Ptr CString -> ()

x86_32 :: String -> Int -> IO String
x86_32 val seed = do
  val' <- withCAStringLen val $ \x -> return x
  let strPtr = strFromCStr val'
  let strLength = strLFromCStr val'
  p <- mallocForeignPtr :: IO(ForeignPtr CString )
  rt <- mallocForeignPtr :: IO(ForeignPtr CString )
  withForeignPtr p $ \ptr -> poke ptr strPtr
  withForeignPtr p $ 
    \ptr -> return $ 
      c_x86_32 ptr strLength (fromIntegral seed) $ US.unsafeForeignPtrToPtr rt
  withForeignPtr rt $ \ ptr -> do cs <- peek ptr; peekCString cs
  where strFromCStr :: CStringLen -> CString
        strFromCStr = fst
        strLFromCStr :: CStringLen -> CInt
        strLFromCStr i = fromIntegral $ snd i