1543e75f50
This envolves adding the requirement, that every Encoding must also be an instance of Eq and Typeable to go into DynEncoding. darcs-hash:20090225035150-a4fee-c7d902e28313929ee9ffe0c6a6b60d8ff4704ae9
77 lines
2.4 KiB
Haskell
77 lines
2.4 KiB
Haskell
{-# LANGUAGE ExistentialQuantification #-}
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module Data.Encoding.Base where
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import Data.Encoding.Exception
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import Data.Encoding.ByteSource
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import Data.Encoding.ByteSink
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import Control.Throws
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import Data.Array as Array
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import Data.Map as Map hiding ((!))
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import Data.Word
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import Data.Char
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import Data.Typeable
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class Encoding enc where
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decodeChar :: ByteSource m => enc -> m Char
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encodeChar :: ByteSink m => enc -> Char -> m ()
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decode :: ByteSource m => enc -> m String
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decode e = untilM sourceEmpty (decodeChar e)
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encode :: ByteSink m => enc -> String -> m ()
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encode e = mapM_ (encodeChar e)
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encodeable :: enc -> Char -> Bool
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data DynEncoding = forall enc. (Encoding enc,Eq enc,Typeable enc) => DynEncoding enc
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instance Encoding DynEncoding where
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decodeChar (DynEncoding e) = decodeChar e
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encodeChar (DynEncoding e) = encodeChar e
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decode (DynEncoding e) = decode e
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encode (DynEncoding e) = encode e
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encodeable (DynEncoding e) = encodeable e
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instance Eq DynEncoding where
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(DynEncoding e1) == (DynEncoding e2) = case cast e2 of
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Nothing -> False
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Just e2' -> e1==e2'
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untilM :: Monad m => m Bool -> m a -> m [a]
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untilM check act = do
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end <- check
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if end
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then return []
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else (do
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x <- act
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xs <- untilM check act
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return (x:xs)
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)
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untilM_ :: Monad m => m Bool -> m a -> m ()
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untilM_ check act = untilM check act >> return ()
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encodeWithMap :: ByteSink m => Map Char Word8 -> Char -> m ()
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encodeWithMap mp c = case Map.lookup c mp of
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Nothing -> throwException $ HasNoRepresentation c
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Just v -> pushWord8 v
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encodeWithMap2 :: ByteSink m => Map Char (Word8,Word8) -> Char -> m ()
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encodeWithMap2 mp c = case Map.lookup c mp of
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Nothing -> throwException $ HasNoRepresentation c
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Just (w1,w2) -> do
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pushWord8 w1
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pushWord8 w2
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decodeWithArray :: ByteSource m => Array Word8 (Maybe Char) -> m Char
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decodeWithArray arr = do
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w <- fetchWord8
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case arr!w of
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Nothing -> throwException $ IllegalCharacter w
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Just c -> return c
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decodeWithArray2 :: ByteSource m => Array (Word8,Word8) (Maybe Char) -> m Char
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decodeWithArray2 arr = do
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w1 <- fetchWord8
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w2 <- fetchWord8
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case arr!(w1,w2) of
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Nothing -> throwException $ IllegalCharacter w1
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Just c -> return c |