End-of-stream emulator WIP

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diff --git a/fig-emulator-gb/src/Fig/Emulator/GB/Utils.hs b/fig-emulator-gb/src/Fig/Emulator/GB/Utils.hs
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+++ b/fig-emulator-gb/src/Fig/Emulator/GB/Utils.hs
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+module Fig.Emulator.GB.Utils where
+
+import Fig.Prelude
+
+import Prelude (fromIntegral)
+
+import Data.Word (Word8, Word16)
+import Data.Int (Int8)
+import Data.Bits
+
+w8w8 :: Word8 -> Word8 -> Word16
+w8w8 high low = shiftL (fromIntegral high) 8 .|. fromIntegral low
+
+w16hi :: Word16 -> Word8
+w16hi v = fromIntegral $ shiftR v 8
+
+w16lo :: Word16 -> Word8
+w16lo v = fromIntegral $ v .&. 0xff
+
+w8bit :: Int -> Word8 -> Bool
+w8bit i v = shiftR v i .&. 0b1 == 1
+
+w8bits2 :: Int -> Word8 -> Word8
+w8bits2 i v = shiftR v (i - 1) .&. 0b11
+
+w8bits3 :: Int -> Word8 -> Word8
+w8bits3 i v = shiftR v (i - 2) .&. 0b111
+
+w8bits4 :: Int -> Word8 -> Word8
+w8bits4 i v = shiftR v (i - 3) .&. 0b1111
+
+flagsw8 :: Bool -> Bool -> Bool -> Bool -> Word8
+flagsw8 z n h c =
+  shiftL (if z then 1 else 0) 7
+  .|. shiftL (if n then 1 else 0) 6
+  .|. shiftL (if h then 1 else 0) 5
+  .|. shiftL (if c then 1 else 0) 4
+
+zext :: Word8 -> Word16
+zext = fromIntegral
+
+sext :: Word8 -> Word16
+sext x = fromIntegral y
+  where
+    y :: Int8
+    y = fromIntegral x
+
+trunc :: Word16 -> Word8
+trunc = fromIntegral
+
+addC :: Bool -> Word8 -> Word8 -> (Word8, Bool)
+addC c x y = (trunc res, shiftR res 8 .&. 1 == 1)
+  where
+    res :: Word16
+    res = sext x + sext y + if c then 1 else 0
+
+addH :: Bool -> Word8 -> Word8 -> Bool
+addH c x y = shiftR res 4 .&. 1 == 1
+  where
+    xlo = x .&. 0xf
+    ylo = y .&. 0xf
+    res :: Word8
+    res = xlo + ylo + if c then 1 else 0
+
+subH :: Word8 -> Word8 -> Bool
+subH x y = w8bits4 3 x < w8bits4 3 y