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module Fig.Emulator.GB.Component.RAM
( compWRAM
) where
import Fig.Prelude
import Prelude (fromIntegral)
import qualified Data.Vector as V
import qualified Data.Vector.Mutable as MV
import Data.Word (Word8)
import Fig.Emulator.GB.Bus
newtype RAMError = RAMError Text
deriving Show
instance Exception RAMError
instance Pretty RAMError where
pretty (RAMError b) = mconcat
[ "internal RAM error: "
, b
]
compWRAM :: (MonadIO m, MonadThrow m) => Addr -> Int -> Component m
compWRAM start size = Component
{ compState = V.replicate size 0 :: V.Vector Word8
, compMatches = \a ->
a >= start && a < end
, compUpdate = \s _ -> pure s
, compWrite = \s ad v -> do
let offset = fromIntegral . unAddr $ ad - start
pure $ V.modify (\ms -> MV.write ms offset v) s
, compRead = \s ad -> do
let offset = fromIntegral . unAddr $ ad - start
case s V.!? offset of
Nothing -> throwM . RAMError $ mconcat
[ "address ", pretty ad, " out of bounds"
]
Just v -> pure v
}
where
end = start + Addr (fromIntegral size)
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