1 files changed, 41 insertions, 0 deletions
diff --git a/fig-emulator-gb/src/Fig/Emulator/GB/Component/RAM.hs b/fig-emulator-gb/src/Fig/Emulator/GB/Component/RAM.hs
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+++ b/fig-emulator-gb/src/Fig/Emulator/GB/Component/RAM.hs
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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 = pure
+  , 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)