From 3a0a7b0a89fd841edd5f25f79cdb877051d0e948 Mon Sep 17 00:00:00 2001
From: LLLL Colonq <llll@colonq>
Date: Tue, 9 Apr 2024 22:35:42 -0400
Subject: End-of-stream emulator WIP

---
 .../src/Fig/Emulator/GB/Component/ROM.hs           | 45 ++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 fig-emulator-gb/src/Fig/Emulator/GB/Component/ROM.hs

(limited to 'fig-emulator-gb/src/Fig/Emulator/GB/Component/ROM.hs')

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
-- 
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