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Diffstat (limited to 'Utility/NotificationBroadcaster.hs')
| -rw-r--r-- | Utility/NotificationBroadcaster.hs | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/Utility/NotificationBroadcaster.hs b/Utility/NotificationBroadcaster.hs index 413ec2d75..b873df655 100644 --- a/Utility/NotificationBroadcaster.hs +++ b/Utility/NotificationBroadcaster.hs @@ -40,14 +40,23 @@ data NotificationHandle = NotificationHandle NotificationBroadcaster Notificatio newNotificationBroadcaster :: IO NotificationBroadcaster newNotificationBroadcaster = atomically $ newTMVar [] -{- Allocates a notification handle for a client to use. -} -newNotificationHandle :: NotificationBroadcaster -> IO NotificationHandle -newNotificationHandle b = NotificationHandle +{- Allocates a notification handle for a client to use. + - + - An immediate notification can be forced the first time waitNotification + - is called on the handle. This is useful in cases where a notification + - may be sent while the new handle is being constructed. Normally, + - such a notification would be missed. Forcing causes extra work, + - but ensures such notifications get seen. + -} +newNotificationHandle :: Bool -> NotificationBroadcaster -> IO NotificationHandle +newNotificationHandle force b = NotificationHandle <$> pure b <*> addclient where addclient = do - s <- newEmptySV + s <- if force + then newSV () + else newEmptySV atomically $ do l <- takeTMVar b putTMVar b $ l ++ [s] |