{-# LANGUAGE ForeignFunctionInterface #-}

import Foreign
import Foreign.C.String
import Foreign.C.Types
import System.Win32.DLL

import Control.Applicative
import Data.Word

type Error_t = Int
type Func = Ptr Word32 -> IO Error_t

foreign import ccall "dynamic" rand_s_func :: FunPtr Func -> Func

rand_s = do
  lib <- loadLibrary "msvcrt.dll"
  rand_s_ptr <- rand_s_func . castPtrToFunPtr <$> getProcAddress lib "rand_s"
  alloca $ \ptr -> rand_s_ptr ptr >> peek ptr

read4Bytes =
  let f x = map (flip mod (2^8) . div x . (2^) . (8*)) [0..3]
  in f <$> rand_s