Switched awaitMessage to continuation-passing style.

1 files changed, 75 insertions, 68 deletions

diff --git a/src/Network/QueryResponse.hs b/src/Network/QueryResponse.hs
index c8a6fa80..190cc73e 100644
--- a/src/Network/QueryResponse.hs
+++ b/src/Network/QueryResponse.hs
@@ -7,6 +7,7 @@
 {-# LANGUAGE PartialTypeSignatures #-}
 {-# LANGUAGE RankNTypes            #-}
 {-# LANGUAGE ScopedTypeVariables   #-}
+{-# LANGUAGE TupleSections         #-}
 module Network.QueryResponse where
 
 #ifdef THREAD_DEBUG
@@ -33,7 +34,55 @@ import System.IO
 import System.IO.Error
 import System.Timeout
 
--- * Using a query\/response 'Client'.
+-- | Three methods are required to implement a datagram based query\/response protocol.
+data Transport err addr x = Transport
+    { -- | Blocks until an inbound packet is available. Returns 'Nothing' when
+      -- no more packets are expected due to a shutdown or close event.
+      -- Otherwise, the packet will be parsed as type /x/ and an origin address
+      -- /addr/.  Parse failure is indicated by the type 'err'.
+      awaitMessage :: forall a. (Maybe (Either err (x, addr)) -> IO a) -> IO a
+      -- | Send an /x/ packet to the given destination /addr/.
+    , sendMessage :: addr -> x -> IO ()
+      -- | Shutdown and clean up any state related to this 'Transport'.
+    , closeTransport :: IO ()
+    }
+
+-- | This function modifies a 'Transport' to use higher-level addresses and
+-- packet representations.  It could be used to change UDP 'ByteString's into
+-- bencoded syntax trees or to add an encryption layer in which addresses have
+-- associated public keys.
+layerTransport ::
+        (x -> addr -> Either err (x', addr'))
+        -- ^ Function that attempts to transform a low-level address/packet
+        -- pair into a higher level representation.
+        -> (x' -> addr' -> (x, addr))
+        -- ^ Function to encode a high-level address/packet into a lower level
+        -- representation.
+        -> Transport err addr x
+        -- ^ The low-level transport to be transformed.
+        -> Transport err addr' x'
+layerTransport parse encode tr =
+    tr { awaitMessage = \kont ->
+                awaitMessage tr $ \m -> kont $ fmap (>>= uncurry parse) m
+       , sendMessage = \addr' msg' -> do
+                let (msg,addr) = encode msg' addr'
+                sendMessage tr addr msg
+       }
+
+addHandler :: (addr -> x -> IO (Maybe (x -> x))) -> Transport err addr x -> Transport err addr x
+addHandler f tr = tr
+    { awaitMessage = \kont -> fix $ \eat -> awaitMessage tr $ \m -> do
+        case m of
+            Just (Right (x, addr)) -> f addr x >>= maybe eat (kont . Just . Right . (, addr) . ($ x))
+            Just (Left  e        ) -> kont $ Just (Left e)
+            Nothing                -> kont $ Nothing
+    }
+
+-- | Modify a 'Transport' to invoke an action upon every received packet.
+onInbound :: (addr -> x -> IO ()) -> Transport err addr x -> Transport err addr x
+onInbound f tr = addHandler (\addr x -> f addr x >> return (Just id)) tr
+
+-- * Using a query\/response client.
 
 -- | Fork a thread that handles inbound packets.  The returned action may be used
 -- to terminate the thread and clean up any related state.
@@ -41,18 +90,18 @@ import System.Timeout
 --  Example usage:
 --
 --  > -- Start client.
---  > quitServer <- forkListener client
+--  > quitServer <- forkListener (clientNet client)
 --  > -- Send a query q, recieve a response r.
 --  > r <- sendQuery client method q
 --  > -- Quit client.
 --  > quitServer
-forkListener :: Client err meth tid addr x -> IO (IO ())
+forkListener :: Transport err addr x -> IO (IO ())
 forkListener client = do
     thread_id <- forkIO $ do
         myThreadId >>= flip labelThread "listener"
-        fix $ handleMessage client
+        fix $ awaitMessage client . const
     return $ do
-        closeTransport (clientNet client)
+        closeTransport client
         killThread thread_id
 
 -- | Send a query to a remote peer.  Note that this funciton will always time
@@ -165,53 +214,6 @@ data MethodSerializer tid addr x meth a b = MethodSerializer
     }
 
 
--- | Three methods are required to implement a datagram based query\/response protocol.
-data Transport err addr x = Transport
-    { -- | Blocks until an inbound packet is available. Returns 'Nothing' when
-      -- no more packets are expected due to a shutdown or close event.
-      -- Otherwise, the packet will be parsed as type /x/ and an origin address
-      -- /addr/.  Parse failure is indicated by the type 'err'.
-      awaitMessage :: IO (Maybe (Either err (x, addr)))
-      -- | Send an /x/ packet to the given destination /addr/.
-    , sendMessage :: addr -> x -> IO ()
-      -- | Shutdown and clean up any state related to this 'Transport'.
-    , closeTransport :: IO ()
-    }
-
--- | This function modifies a 'Transport' to use higher-level addresses and
--- packet representations.  It could be used to change UDP 'ByteString's into
--- bencoded syntax trees or to add an encryption layer in which addresses have
--- associated public keys.
-layerTransport ::
-        (x -> addr -> Either err (x', addr'))
-        -- ^ Function that attempts to transform a low-level address/packet
-        -- pair into a higher level representation.
-        -> (x' -> addr' -> (x, addr))
-        -- ^ Function to encode a high-level address/packet into a lower level
-        -- representation.
-        -> Transport err addr x
-        -- ^ The low-level transport to be transformed.
-        -> Transport err addr' x'
-layerTransport parse encode tr =
-    tr { awaitMessage = do
-                m <- awaitMessage tr
-                return $ fmap (>>= uncurry parse) m
-       , sendMessage = \addr' msg' -> do
-                let (msg,addr) = encode msg' addr'
-                sendMessage tr addr msg
-       }
-
--- | Modify a 'Transport' to invoke an action upon every received packet.
-onInbound :: (addr -> x -> IO ()) -> Transport err addr x -> Transport err addr x
-onInbound f tr = tr
-    { awaitMessage = do
-        m <- awaitMessage tr
-        case m of
-            Just (Right (x, addr)) -> f addr x
-            _                      -> return ()
-        return m
-    }
-
 -- | To dipatch responses to our outbound queries, we require three primitives.
 -- See the 'transactionMethods' function to create these primitives out of a
 -- lookup table and a generator for transaction ids.
@@ -360,21 +362,24 @@ contramapE f (ErrorReporter pe mh unk tim)
 -- or throws an exception.
 handleMessage ::
     Client err meth tid addr x
-    -> IO ()
-    -> IO ()
-handleMessage (Client net d err pending whoami responseID) again = do
-  awaitMessage net >>= \case
-    Just (Left e)              -> do reportParseError err e
-                                     again
-    Just (Right (plain, addr)) -> do
+    -> addr
+    -> x
+    -> IO (Maybe (x -> x))
+handleMessage (Client net d err pending whoami responseID) addr plain = do
+    -- Just (Left e)              -> do reportParseError err e
+    --                                  return $! Just id
+    -- Just (Right (plain, addr)) -> do
         case classifyInbound d plain of
             IsQuery meth tid -> case lookupHandler d meth of
-                                Nothing -> reportMissingHandler err meth addr plain
+                                Nothing -> do reportMissingHandler err meth addr plain
+                                              return $! Just id
                                 Just m  -> do
                                   self <- whoami (Just addr)
                                   tid' <- responseID tid
-                                  either (reportParseError err)
-                                         (>>= mapM_ (sendMessage net addr))
+                                  either (\e -> do reportParseError err e
+                                                   return $! Just id)
+                                         (>>= \m -> do mapM_ (sendMessage net addr) m
+                                                       return $! Nothing)
                                          (dispatchQuery m tid' self plain addr)
             IsResponse tid -> do
                 action <- atomically $ do
@@ -383,9 +388,10 @@ handleMessage (Client net d err pending whoami responseID) again = do
                     writeTVar pending ts
                     return action
                 action
-            IsUnknown e -> reportUnknown err addr plain e
-        again
-    Nothing -> return ()
+                return $! Nothing
+            IsUnknown e -> do reportUnknown err addr plain e
+                              return $! Just id
+    -- Nothing -> return $! id
 
 -- * UDP Datagrams.
 
@@ -420,9 +426,10 @@ udpTransport bind_address = do
     setSocketOption sock IPv6Only 0
   bind sock bind_address
   return Transport
-    { awaitMessage = handle (ignoreEOF $ Just $ Right (B.empty, SockAddrInet 0 0)) $ do
-        r <- B.recvFrom sock udpBufferSize
-        return $ Just $ Right r
+    { awaitMessage = \kont -> do
+        r <- handle (ignoreEOF $ Just $ Right (B.empty, SockAddrInet 0 0)) $ do
+                Just . Right <$!> B.recvFrom sock udpBufferSize
+        kont $! r
     , sendMessage = \addr bs -> void $ B.sendTo sock bs addr
         -- TODO: sendTo: does not exist (Network is unreachable)
         --       Occurs when IPv6 network is not available.