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1+{-# LANGUAGE BangPatterns #-}
2+module BackgroundWriter
3+ ( Scope
4+ , withScope
5+ , writeBinary
6+ )
7+ where
8+
9+
10+import Control.Concurrent (forkIO)
11+import Control.Concurrent.MVar (MVar, newEmptyMVar, newMVar, putMVar, takeMVar)
12+import qualified Data.Binary as Binary
13+import Data.Foldable (traverse_)
14+
15+import qualified File
16+
17+
18+
19+-- BACKGROUND WRITER
20+
21+
22+newtype Scope =
23+ Scope (MVar [MVar ()])
24+
25+
26+withScope :: (Scope -> IO a) -> IO a
27+withScope callback =
28+ do workList <- newMVar []
29+ result <- callback (Scope workList)
30+ mvars <- takeMVar workList
31+ traverse_ takeMVar mvars
32+ return result
33+
34+
35+writeBinary :: (Binary.Binary a) => Scope -> FilePath -> a -> IO ()
36+writeBinary (Scope workList) path value =
37+ do mvar <- newEmptyMVar
38+ _ <- forkIO (File.writeBinary path value >> putMVar mvar ())
39+ oldWork <- takeMVar workList
40+ let !newWork = mvar:oldWork
41+ putMVar workList newWork
42+