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flushTQueue: only perform writeTVar when necessary #6

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Merged
merged 1 commit into from
Mar 22, 2018
Merged

flushTQueue: only perform writeTVar when necessary #6

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6 changes: 3 additions & 3 deletions Control/Concurrent/STM/TQueue.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ module Control.Concurrent.STM.TQueue (
) where

import GHC.Conc

import Control.Monad (unless)
import Data.Typeable (Typeable)

-- | 'TQueue' is an abstract type representing an unbounded FIFO channel.
Expand Down Expand Up @@ -115,8 +115,8 @@ flushTQueue :: TQueue a -> STM [a]
flushTQueue (TQueue read write) = do
xs <- readTVar read
ys <- readTVar write
writeTVar read []
writeTVar write []
unless (null xs) $ writeTVar read []
unless (null ys) $ writeTVar write []
return (xs ++ reverse ys)

-- | Get the next value from the @TQueue@ without removing it,
Expand Down