io-memoize 1.1.0.0 → 1.1.1.0

raw patch · 2 files changed

+28/−24 lines, 2 filesPVP ok

version bump matches the API change (PVP)

API changes (from Hackage documentation)

Files

• io-memoize.cabal +6/−3
• src/Control/Concurrent/Cache.hs +22/−21

@@ -1,5 +1,5 @@ name:                io-memoize-version:             1.1.0.0+version:             1.1.1.0 synopsis:            Memoize IO actions description:   Transform an IO action into a similar IO action@@ -10,7 +10,7 @@   .   (1) lazily (might never be performed)   .-  (2) eagerly (concurrent)+  (2) eagerly (concurrently performed)   .   Special thanks to shachaf and headprogrammingczar from #haskell irc   for helping me reason about the behavior of this library.@@ -22,6 +22,9 @@ maintainer:          danburton.email@gmail.com copyright:           (c) 2014 Dan Burton +homepage:            https://github.com/DanBurton/io-memoize+bug-reports:         https://github.com/DanBurton/io-memoize/issues+ category:            System build-type:          Simple cabal-version:       >=1.8@@ -39,4 +42,4 @@ source-repository this   type:     git   location: git://github.com/DanBurton/io-memoize-  tag:      io-memoize-1.0.0.0+  tag:      io-memoize-1.1.1.0

@@ -1,29 +1,30 @@+{-# LANGUAGE DeriveDataTypeable #-} module Control.Concurrent.Cache (Cache, newCache, fetch) where  import Control.Concurrent.MVar-import Data.IORef+import Control.Monad (liftM)+import Data.Typeable (Typeable) --- | A thread-safe write-once cache.-newtype Cache a = Cache {-  -- | Fetch the value stored in the cache,-  -- or call the supplied fallback and store the result,-  -- if the cache is empty.-  fetch :: IO a -> IO a-}+-- | A thread-safe write-once cache. If you need more functionality,+-- (e.g. multiple write, cache clearing) use an 'MVar' instead.+newtype Cache a = Cache (MVar (Maybe a))+  deriving (Eq, Typeable) +-- | Fetch the value stored in the cache,+-- or call the supplied fallback and store the result,+-- if the cache is empty.+fetch :: Cache a -> IO a -> IO a+fetch (Cache var) action = go where+  go = readMVar var >>= \m -> case m of+    Just a -> return a+    Nothing -> do+      modifyMVar_ var $ \m' -> case m' of+        Just a -> return (Just a)+        Nothing -> liftM Just action+      go+ -- | Create an empty cache. newCache :: IO (Cache a) newCache = do-  b <- newMVar True-  r <- newIORef undefined-  return (cache b r)--cache :: MVar Bool -> IORef a -> Cache a-cache b r = Cache $ \action -> do-  modifyMVar_ b $ \isEmpty ->-    if isEmpty-      then do v <- action-              writeIORef r v-              return False-      else return False-  readIORef r+  var <- newMVar Nothing+  return (Cache var)