content: {-# LANGUAGE BangPatterns #-}
  {-# LANGUAGE CPP          #-}
  
  module Snap.Internal.Http.Server.Common
    ( atomicModifyIORef'
    , eatException
    ) where
  
  import           Control.Exception (SomeException, catch)
  import           Control.Monad     (void)
  import           Prelude           (IO, return, ($!))
  
  #if MIN_VERSION_base(4,6,0)
  ------------------------------------------------------------------------------
  import           Data.IORef        (atomicModifyIORef')
  
  #else
  ------------------------------------------------------------------------------
  import           Data.IORef        (IORef, atomicModifyIORef)
  import           Prelude           (seq)
  
  
  ------------------------------------------------------------------------------
  -- | Strict version of 'atomicModifyIORef'.  This forces both the value stored
  -- in the 'IORef' as well as the value returned.
  atomicModifyIORef' :: IORef a -> (a -> (a,b)) -> IO b
  atomicModifyIORef' ref f = do
      b <- atomicModifyIORef ref
              (\x -> let (a, b) = f x
                      in (a, a `seq` b))
      b `seq` return b
  #endif
  
  
  ------------------------------------------------------------------------------
  eatException :: IO a -> IO ()
  eatException m = void m `catch` f
    where
      f :: SomeException -> IO ()
      f !_ = return $! ()
  