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{-# LANGUAGE GADTs #-}
{-# LANGUAGE RankNTypes, ScopedTypeVariables #-}
{-# OPTIONS_GHC -fno-warn-name-shadowing #-}
--
-- (c) The University of Glasgow 2002-2006
--
-- Serialized values
module GHC.Serialized (
-- * Main Serialized data type
Serialized(..),
-- * Going into and out of 'Serialized'
toSerialized, fromSerialized,
-- * Handy serialization functions
serializeWithData, deserializeWithData,
) where
import Prelude -- See note [Why do we import Prelude here?]
import Data.Bits
import Data.Word ( Word8 )
import Data.Data
-- | Represents a serialized value of a particular type. Attempts can be made to deserialize it at certain types
data Serialized = Serialized TypeRep [Word8]
-- | Put a Typeable value that we are able to actually turn into bytes into a 'Serialized' value ready for deserialization later
toSerialized :: forall a. Typeable a => (a -> [Word8]) -> a -> Serialized
toSerialized serialize what = Serialized (typeOf what) (serialize what)
-- | If the 'Serialized' value contains something of the given type, then use the specified deserializer to return @Just@ that.
-- Otherwise return @Nothing@.
fromSerialized :: forall a. Typeable a => ([Word8] -> a) -> Serialized -> Maybe a
fromSerialized deserialize (Serialized the_type bytes)
| the_type == rep = Just (deserialize bytes)
| otherwise = Nothing
where rep = typeRep (Proxy :: Proxy a)
-- | Use a 'Data' instance to implement a serialization scheme dual to that of 'deserializeWithData'
serializeWithData :: Data a => a -> [Word8]
serializeWithData what = serializeWithData' what []
serializeWithData' :: Data a => a -> [Word8] -> [Word8]
serializeWithData' what = fst $ gfoldl (\(before, a_to_b) a -> (before . serializeWithData' a, a_to_b a))
(\x -> (serializeConstr (constrRep (toConstr what)), x))
what
-- | Use a 'Data' instance to implement a deserialization scheme dual to that of 'serializeWithData'
deserializeWithData :: Data a => [Word8] -> a
deserializeWithData = snd . deserializeWithData'
deserializeWithData' :: forall a. Data a => [Word8] -> ([Word8], a)
deserializeWithData' bytes = deserializeConstr bytes $ \constr_rep bytes ->
gunfold (\(bytes, b_to_r) -> let (bytes', b) = deserializeWithData' bytes in (bytes', b_to_r b))
(\x -> (bytes, x))
(repConstr (dataTypeOf (undefined :: a)) constr_rep)
serializeConstr :: ConstrRep -> [Word8] -> [Word8]
serializeConstr (AlgConstr ix) = serializeWord8 1 . serializeInt ix
serializeConstr (IntConstr i) = serializeWord8 2 . serializeInteger i
serializeConstr (FloatConstr r) = serializeWord8 3 . serializeRational r
serializeConstr (CharConstr c) = serializeWord8 4 . serializeChar c
deserializeConstr :: [Word8] -> (ConstrRep -> [Word8] -> a) -> a
deserializeConstr bytes k = deserializeWord8 bytes $ \constr_ix bytes ->
case constr_ix of
1 -> deserializeInt bytes $ \ix -> k (AlgConstr ix)
2 -> deserializeInteger bytes $ \i -> k (IntConstr i)
3 -> deserializeRational bytes $ \r -> k (FloatConstr r)
4 -> deserializeChar bytes $ \c -> k (CharConstr c)
x -> error $ "deserializeConstr: unrecognised serialized constructor type " ++ show x ++ " in context " ++ show bytes
serializeFixedWidthNum :: forall a. (Integral a, FiniteBits a) => a -> [Word8] -> [Word8]
serializeFixedWidthNum what = go (finiteBitSize what) what
where
go :: Int -> a -> [Word8] -> [Word8]
go size current rest
| size <= 0 = rest
| otherwise = fromIntegral (current .&. 255) : go (size - 8) (current `shiftR` 8) rest
deserializeFixedWidthNum :: forall a b. (Integral a, FiniteBits a) => [Word8] -> (a -> [Word8] -> b) -> b
deserializeFixedWidthNum bytes k = go (finiteBitSize (undefined :: a)) bytes k
where
go :: Int -> [Word8] -> (a -> [Word8] -> b) -> b
go size bytes k
| size <= 0 = k 0 bytes
| otherwise = case bytes of
(byte:bytes) -> go (size - 8) bytes (\x -> k ((x `shiftL` 8) .|. fromIntegral byte))
[] -> error "deserializeFixedWidthNum: unexpected end of stream"
serializeEnum :: (Enum a) => a -> [Word8] -> [Word8]
serializeEnum = serializeInt . fromEnum
deserializeEnum :: Enum a => [Word8] -> (a -> [Word8] -> b) -> b
deserializeEnum bytes k = deserializeInt bytes (k . toEnum)
serializeWord8 :: Word8 -> [Word8] -> [Word8]
serializeWord8 x = (x:)
deserializeWord8 :: [Word8] -> (Word8 -> [Word8] -> a) -> a
deserializeWord8 (byte:bytes) k = k byte bytes
deserializeWord8 [] _ = error "deserializeWord8: unexpected end of stream"
serializeInt :: Int -> [Word8] -> [Word8]
serializeInt = serializeFixedWidthNum
deserializeInt :: [Word8] -> (Int -> [Word8] -> a) -> a
deserializeInt = deserializeFixedWidthNum
serializeRational :: (Real a) => a -> [Word8] -> [Word8]
serializeRational = serializeString . show . toRational
deserializeRational :: (Fractional a) => [Word8] -> (a -> [Word8] -> b) -> b
deserializeRational bytes k = deserializeString bytes (k . fromRational . read)
serializeInteger :: Integer -> [Word8] -> [Word8]
serializeInteger = serializeString . show
deserializeInteger :: [Word8] -> (Integer -> [Word8] -> a) -> a
deserializeInteger bytes k = deserializeString bytes (k . read)
serializeChar :: Char -> [Word8] -> [Word8]
serializeChar = serializeString . show
deserializeChar :: [Word8] -> (Char -> [Word8] -> a) -> a
deserializeChar bytes k = deserializeString bytes (k . read)
serializeString :: String -> [Word8] -> [Word8]
serializeString = serializeList serializeEnum
deserializeString :: [Word8] -> (String -> [Word8] -> a) -> a
deserializeString = deserializeList deserializeEnum
serializeList :: (a -> [Word8] -> [Word8]) -> [a] -> [Word8] -> [Word8]
serializeList serialize_element xs = serializeInt (length xs) . foldr (.) id (map serialize_element xs)
deserializeList :: forall a b. (forall c. [Word8] -> (a -> [Word8] -> c) -> c)
-> [Word8] -> ([a] -> [Word8] -> b) -> b
deserializeList deserialize_element bytes k = deserializeInt bytes $ \len bytes -> go len bytes k
where
go :: Int -> [Word8] -> ([a] -> [Word8] -> b) -> b
go len bytes k
| len <= 0 = k [] bytes
| otherwise = deserialize_element bytes (\elt bytes -> go (len - 1) bytes (k . (elt:)))
|
