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|
{- DBus utilities
-
- Copyright 2012 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
{-# LANGUAGE OverloadedStrings, ScopedTypeVariables #-}
module Utility.DBus where
import Utility.PartialPrelude
import Utility.Exception
import DBus.Client
import DBus
import Data.Maybe
import Control.Concurrent
import Control.Exception as E
type ServiceName = String
listServiceNames :: Client -> IO [ServiceName]
listServiceNames client = do
reply <- callDBus client "ListNames" []
return $ fromMaybe [] $ fromVariant =<< headMaybe (methodReturnBody reply)
callDBus :: Client -> MemberName -> [Variant] -> IO MethodReturn
callDBus client name params = call_ client $
(methodCall "/org/freedesktop/DBus" "org.freedesktop.DBus" name)
{ methodCallDestination = Just "org.freedesktop.DBus"
, methodCallBody = params
}
{- Connects to the bus, and runs the client action.
-
- Throws a ClientError, and closes the connection if it fails to
- process an incoming message, or if the connection is lost.
- Unlike DBus's usual interface, this error is thrown at the top level,
- rather than inside the clientThreadRunner, so it can be caught, and
- runClient re-run as needed. -}
runClient :: IO (Maybe Address) -> (Client -> IO ()) -> IO ()
runClient getaddr clientaction = do
env <- getaddr
case env of
Nothing -> throwIO (clientError "runClient: unable to determine DBUS address")
Just addr -> do
{- The clientaction will set up listeners, which
- run in a different thread. We block while
- they're running, until our threadrunner catches
- a ClientError, which it will put into the MVar
- to be rethrown here. -}
mv <- newEmptyMVar
let tr = threadrunner (putMVar mv)
let opts = defaultClientOptions { clientThreadRunner = tr }
client <- connectWith opts addr
clientaction client
e <- takeMVar mv
disconnect client
throw e
where
threadrunner storeerr io = loop
where
loop = catchClientError (io >> loop) storeerr
{- Connects to the bus, and runs the client action.
-
- If the connection is lost, runs onretry, which can do something like
- a delay, or printing a warning, and has a state value (useful for
- exponential backoff). Once onretry returns, the connection is retried.
-}
persistentClient :: IO (Maybe Address) -> v -> (SomeException -> v -> IO v) -> (Client -> IO ()) -> IO ()
persistentClient getaddr v onretry clientaction =
{- runClient can fail with not just ClientError, but also other
- things, if dbus is not running. Let async exceptions through. -}
runClient getaddr clientaction `catchNonAsync` retry
where
retry e = do
v' <- onretry e v
persistentClient getaddr v' onretry clientaction
{- Catches only ClientError -}
catchClientError :: IO () -> (ClientError -> IO ()) -> IO ()
catchClientError io handler =
either handler return =<< (E.try io :: IO (Either ClientError ()))
|
