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{- git-annex assistant transfer slots
-
- Copyright 2012 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Assistant.TransferSlots where
import Control.Exception
import Control.Concurrent
import Common.Annex
import Assistant.ThreadedMonad
type TransferSlots = QSemN
{- Number of concurrent transfers allowed to be run from the assistant.
-
- Transfers launched by other means, including by remote assistants,
- do not currently take up slots.
-}
numSlots :: Int
numSlots = 1
newTransferSlots :: IO TransferSlots
newTransferSlots = newQSemN numSlots
{- Waits until a transfer slot becomes available, and runs a transfer
- action in the slot, in its own thread. Note that this thread is
- subject to being killed when the transfer is canceled. -}
inTransferSlot :: TransferSlots -> ThreadState -> Annex a -> IO ThreadId
inTransferSlot s st a = do
waitQSemN s 1
forkIO $ bracket_ noop done run
where
done = transferComplete s
run = unsafeRunThreadState st a
{- Call when a transfer is complete. -}
transferComplete :: TransferSlots -> IO ()
transferComplete s = signalQSemN s 1
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