ligo/tools/lsp/squirrel/src/Debouncer.hs

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module Debouncer (debounced) where
import Control.Monad.Catch
import Control.Monad
import Control.Concurrent
-- | Ensure the function is run in single thread, w/o overlapping.
--
-- If called concurently, everyone will get results of the winner.
--
-- If called, waits for next result to arrive.
--
-- If function throws an error, will rethrow it in caller thread.
--
debounced :: forall s r. (s -> IO r) -> IO (s -> IO r)
debounced act = do
i <- newEmptyMVar
o <- newEmptyMVar
mask_ do
forkIO do
forever do
_ <- tryTakeMVar o
i' <- takeMVar i
o' <- try $ act i'
putMVar o (o' :: Either SomeException r)
return $ \i' -> do
_ <- tryTakeMVar i
putMVar i i'
readMVar o >>= either throwM return
_test :: IO ([Int] -> IO Int)
_test = debounced \s -> do
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threadDelay 2000000
unless (odd (length s)) do
error "even"
return (length s)