1 files changed, 39 insertions, 0 deletions
diff --git a/Utility/TSet.hs b/Utility/TSet.hs
new file mode 100644
index 000000000..24d345477
--- /dev/null
+++ b/Utility/TSet.hs
@@ -0,0 +1,39 @@
+{- Transactional sets
+ -
+ - Copyright 2012 Joey Hess <joey@kitenet.net>
+ -}
+
+module Utility.TSet where
+
+import Common
+
+import Control.Concurrent.STM
+
+type TSet = TChan
+
+runTSet :: STM a -> IO a
+runTSet = atomically
+
+newTSet :: IO (TSet a)
+newTSet = atomically newTChan
+
+{- Gets the contents of the TSet. Blocks until at least one item is
+ - present. -}
+getTSet :: TSet a -> IO [a]
+getTSet tset = runTSet $ do
+	c <- readTChan tset
+	go [c]
+	where
+		go l = do
+			v <- tryReadTChan tset
+			case v of
+				Nothing -> return l
+				Just c -> go (c:l)
+
+{- Puts items into a TSet. -}
+putTSet :: TSet a -> [a] -> IO ()
+putTSet tset vs = runTSet $ mapM_ (writeTChan tset) vs
+
+{- Put a single item into a TSet. -}
+putTSet1 :: TSet a -> a -> IO ()
+putTSet1 tset v = void $ runTSet $ writeTChan tset v