End-of-stream emulator WIP

1 files changed, 45 insertions, 0 deletions

diff --git a/fig-emulator-gb/src/Fig/Emulator/GB/Component/ROM.hs b/fig-emulator-gb/src/Fig/Emulator/GB/Component/ROM.hs
new file mode 100644
index 0000000..b5ea24f
--- /dev/null
+++ b/fig-emulator-gb/src/Fig/Emulator/GB/Component/ROM.hs
@@ -0,0 +1,45 @@
+module Fig.Emulator.GB.Component.ROM
+  ( compROM
+  ) where
+
+import Fig.Prelude
+import Prelude (fromIntegral)
+
+import qualified Data.Vector as V
+import qualified Data.ByteString as BS
+
+import Fig.Emulator.GB.Bus
+
+newtype ROMError = ROMError Text
+  deriving Show
+instance Exception ROMError
+instance Pretty ROMError where
+  pretty (ROMError b) = mconcat
+    [ "internal ROM error: "
+    , b
+    ]
+
+-- | Initialize base ROM (no mapper) from a ByteString
+compROM :: (MonadIO m, MonadThrow m) => ByteString -> Component m
+compROM bs = Component
+  { compState = V.fromList $ BS.unpack bs
+  , compMatches = \a ->
+      a >= start && a < end
+  , compUpdate = pure
+  , compWrite = \s _ad _v ->
+      pure s
+      -- throwM . ROMError $ mconcat
+      -- [ "tried to write to ROM at ", pretty ad
+      -- ]
+  , compRead = \s ad -> do
+      let offset = fromIntegral . unAddr $ ad - start
+      case s V.!? offset of
+        Nothing -> throwM . ROMError $ mconcat
+          [ "address ", pretty ad, " out of bounds"
+          ]
+        Just v -> pure v
+  }
+  where
+    start = 0x0000
+    -- end = 0x4000
+    end = 0x8000