ef7b53e784
Now when the dbus connection is dropped, it'll fall back to polling. I could make it try to reconnect, but there's a FD leak in the dbus library, so not yet.
85 lines
2.9 KiB
Haskell
85 lines
2.9 KiB
Haskell
{- DBus utilities
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-
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- Copyright 2012 Joey Hess <joey@kitenet.net>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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{-# LANGUAGE OverloadedStrings #-}
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module Utility.DBus where
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import DBus.Client
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import DBus
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import Data.Maybe
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import Control.Concurrent
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import Control.Exception as E
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type ServiceName = String
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listServiceNames :: Client -> IO [ServiceName]
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listServiceNames client = do
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reply <- callDBus client "ListNames" []
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return $ fromMaybe [] $ fromVariant (methodReturnBody reply !! 0)
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callDBus :: Client -> MemberName -> [Variant] -> IO MethodReturn
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callDBus client name params = call_ client $
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(methodCall "/org/freedesktop/DBus" "org.freedesktop.DBus" name)
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{ methodCallDestination = Just "org.freedesktop.DBus"
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, methodCallBody = params
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}
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{- Connects to the bus, and runs the client action.
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-
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- Throws a ClientError, and closes the connection if it fails to
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- process an incoming message, or if the connection is lost.
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- Unlike DBus's usual interface, this error is thrown at the top level,
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- rather than inside the clientThreadRunner, so it can be caught, and
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- runClient re-run as needed. -}
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runClient :: IO (Maybe Address) -> (Client -> IO ()) -> IO ()
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runClient getaddr clientaction = do
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env <- getaddr
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case env of
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Nothing -> throwIO (clientError "runClient: unable to determine DBUS address")
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Just addr -> do
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{- The clientaction will set up listeners, which
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- run in a different thread. We block while
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- they're running, until our threadrunner catches
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- a ClientError, which it will put into the MVar
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- to be rethrown here. -}
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mv <- newEmptyMVar
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let tr = threadrunner (putMVar mv)
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let opts = defaultClientOptions { clientThreadRunner = tr }
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client <- connectWith opts addr
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clientaction client
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e <- takeMVar mv
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disconnect client
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throw e
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where
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threadrunner storeerr io = loop
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where
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loop = catchClientError (io >> loop) storeerr
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{- Connects to the bus, and runs the client action.
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-
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- If the connection is lost, runs onretry, which can do something like
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- a delay, or printing a warning, and has a state value (useful for
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- exponential backoff). Once onretry returns, the connection is retried.
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-
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- Warning: Currently connectWith can throw a SocketError and leave behind
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- an open FD. So each retry leaks one FD. -}
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persistentClient :: IO (Maybe Address) -> v -> (SomeException -> v -> IO v) -> (Client -> IO ()) -> IO ()
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persistentClient getaddr v onretry clientaction = do
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{- runClient can fail with not just ClientError, but also other
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- things, if dbus is not running. -}
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r <- E.try (runClient getaddr clientaction) :: IO (Either SomeException ())
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either retry return r
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where
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retry e = do
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v' <- onretry e v
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persistentClient getaddr v' onretry clientaction
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{- Catches only ClientError -}
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catchClientError :: IO () -> (ClientError -> IO ()) -> IO ()
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catchClientError io handler = do
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either handler return =<< (E.try io :: IO (Either ClientError ()))
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