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module Data.Accessor.ByteSource where
import qualified Control.Monad.Trans.State as State
import Control.Monad.Trans.State (StateT, )
import Control.Monad.Trans.Class (lift, )
import Data.Word (Word8, )
class ByteCompatible byte where
toByte :: byte -> Word8
instance ByteCompatible Word8 where
toByte = id
class ByteStream s where
getWord8 :: MonadFail m => s -> m (Word8, s)
instance ByteCompatible byte => ByteStream [byte] where
getWord8 xs =
case xs of
(c:cs) -> return (toByte c, cs)
_ -> fail "ByteStream: no more byte available"
class Monad source => ByteSource source where
readWord8 :: source Word8
instance (ByteStream s, MonadFail m) => ByteSource (StateT s m) where
readWord8 =
do xs <- State.get
(c,cs) <- lift (getWord8 xs)
State.put cs
return c
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