skeleton C library for calling kqueue

Utility/Kqueue.hs

@@ -0,0 +1,31 @@
+{- BSD kqueue file modification notification interface
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# LANGUAGE ForeignFunctionInterface #-}
+
+module Utility.Kqueue ( waitChange ) where
+
+import Common
+
+import System.Posix.Types
+import Foreign.C.Types
+import Foreign.C.Error
+import Foreign.Ptr
+import Foreign.Marshal
+
+foreign import ccall unsafe "libkqueue.h waitchange" c_waitchange
+	:: Ptr Fd -> IO Fd
+
+waitChange :: [Fd] -> IO (Maybe Fd)
+waitChange fds = withArray fds $ \c_fds -> do
+	ret <- c_waitchange c_fds
+	ifM (safeErrno <$> getErrno)
+		( return $ Just ret
+		, return Nothing
+		)
+	where
+		safeErrno (Errno v) = v == 0