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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
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