From f57e800a1d1a8e9f2bed34428f7f58a375f178fb Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Sun, 11 Jul 2021 17:56:34 +0200
Subject: WIP splitting of Target module and towards parallel builds

---
 Coolbal/DataVersionTag.hs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 Coolbal/DataVersionTag.hs

(limited to 'Coolbal/DataVersionTag.hs')

diff --git a/Coolbal/DataVersionTag.hs b/Coolbal/DataVersionTag.hs
new file mode 100644
index 0000000..a994e90
--- /dev/null
+++ b/Coolbal/DataVersionTag.hs
@@ -0,0 +1,22 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE KindSignatures #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
+module Coolbal.DataVersionTag where
+
+import Data.Binary
+import GHC.TypeNats
+
+
+data DataVersionTag (n :: Nat) = DataVersionTag
+  deriving (Show, Eq, Ord)
+
+instance (KnownNat n, n <= 255) => Binary (DataVersionTag n) where
+    put v = putWord8 (fromIntegral (natVal v))
+    get = do
+        b <- getWord8
+        let result = DataVersionTag :: DataVersionTag n
+        if b == fromIntegral (natVal result)
+            then return result
+            else fail ("DataVersionTag: read version " ++ show b ++ ", application expects version " ++ show (natVal result))
-- 
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