1 files changed, 34 insertions, 0 deletions
diff --git a/src/Cache.hs b/src/Cache.hs
new file mode 100644
index 0000000..d2fd49e
--- /dev/null
+++ b/src/Cache.hs
@@ -0,0 +1,34 @@
+module Cache (Cache, new, read, write) where
+
+import qualified System.Posix.Types as T
+import qualified Data.IORef as IOR
+import qualified Data.Set as S
+import qualified Data.Map as M
+
+data WetCache k v = WC
+  { cTimeStamps :: S.Set (T.EpochTime, k)
+  , cByKey :: M.Map k (T.EpochTime, v)
+  , cDirty :: S.Set k
+  }
+
+data Cache k v = Cache
+  { cWetCache :: IOR.IORef (WetCache k v)
+  , cRead :: k -> IO v
+  , cWrite :: k -> v -> IO ()
+  , cMaxSize :: Int
+  }
+
+new :: (k -> IO v) -> (k -> v -> IO ()) -> Int -> IO Cache
+new r w size = Cache <$> IOR.newIORef CI
+  { cTimeStamps=S.empty, cByKey=M.empty, cDirty=S.empty, cRead=r, cWrite=w
+  , cMaxSize=size }
+
+readMiss :: Cache k v -> k -> IO v
+readMiss r k =
+
+read :: Cache k v -> k -> IO v
+read r k = do
+  CI { cByKey, .. } <- IOR.readIORef r
+  case M.lookup k cByKey of
+    (_, v) -> return v
+    Nothing -> readMiss r k