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21 lines
666 B
Haskell
21 lines
666 B
Haskell
module GF.Source.SharedString (shareString) where
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import Data.Map as M
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import Data.IORef
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import qualified Data.ByteString.Char8 as BS
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import System.IO.Unsafe (unsafePerformIO)
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{-# NOINLINE stringPoolRef #-}
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stringPoolRef :: IORef (M.Map BS.ByteString BS.ByteString)
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stringPoolRef = unsafePerformIO $ newIORef M.empty
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{-# NOINLINE shareString #-}
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shareString :: BS.ByteString -> BS.ByteString
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shareString s = unsafePerformIO $ do
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stringPool <- readIORef stringPoolRef
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case M.lookup s stringPool of
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Just s' -> return s'
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Nothing -> do let s' = BS.copy s
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writeIORef stringPoolRef $! M.insert s' s' stringPool
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return s'
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