1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
{- making the Annex monad available across threads
-
- Copyright 2012 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU AGPL version 3 or higher.
-}
module Assistant.Types.ThreadedMonad where
import Annex.Common
import qualified Annex
import Control.Concurrent
import Data.Tuple
{- The Annex state is stored in a MVar, so that threaded actions can access
- it. -}
type ThreadState = MVar (Annex.AnnexState, Annex.AnnexRead)
{- Stores the Annex state in a MVar.
-
- Once the action is finished, retrieves the state from the MVar.
-}
withThreadState :: (ThreadState -> Annex a) -> Annex a
withThreadState a = do
state <- Annex.getState id
rd <- Annex.getRead id
mvar <- liftIO $ newMVar (state, rd)
r <- a mvar
newstate <- liftIO $ fst <$> takeMVar mvar
Annex.changeState (const newstate)
return r
{- Runs an Annex action, using the state from the MVar.
-
- This serializes calls by threads; only one thread can run in Annex at a
- time. -}
runThreadState :: ThreadState -> Annex a -> IO a
runThreadState mvar a = modifyMVar mvar $ \v -> swap <$> Annex.run v a
|
