1 files changed, 44 insertions, 0 deletions
diff --git a/fig-bus/src/Fig/Bus/Binary/Utils.hs b/fig-bus/src/Fig/Bus/Binary/Utils.hs
new file mode 100644
index 0000000..734c7c9
--- /dev/null
+++ b/fig-bus/src/Fig/Bus/Binary/Utils.hs
@@ -0,0 +1,44 @@
+module Fig.Bus.Binary.Utils where
+
+import Fig.Prelude
+
+import Data.Word (Word8, Word32)
+import Data.Bits ((.|.), (.&.), shiftL, shiftR)
+import Data.ByteString (hPut, hGet)
+import qualified Data.ByteString as BS
+
+newtype EventType = EventType ByteString
+  deriving (Show, Eq, Ord)
+
+intFromLEBytes :: [Word8] -> Int
+intFromLEBytes [] = 0
+intFromLEBytes (x:xs) = shiftL (intFromLEBytes xs) 8 .|. fromIntegral x
+
+readLengthPrefixed :: Handle -> IO (Maybe ByteString)
+readLengthPrefixed h = do
+  n <- hGet h 4
+  case intFromLEBytes (BS.unpack n) of
+    0 -> pure Nothing
+    len -> do
+      x <- hGet h len
+      pure $ Just x
+
+
+readEvent :: Handle -> IO (Maybe EventType)
+readEvent h = do
+  mb <- readLengthPrefixed h
+  pure $ EventType <$> mb
+
+writeLengthPrefixed :: Handle -> ByteString -> IO ()
+writeLengthPrefixed h d = do
+  let l :: Word32 = fromIntegral $ BS.length d
+  let bytes =
+        [ fromIntegral $ l .&. 0xff
+        , fromIntegral $ shiftR l 8 .&. 0xff
+        , fromIntegral $ shiftR l 16 .&. 0xff
+        , fromIntegral $ shiftR l 24 .&. 0xff
+        ]
+  hPut h $ BS.pack bytes <> d 
+
+writeEvent :: Handle -> EventType -> IO ()
+writeEvent h (EventType d) = writeLengthPrefixed h d