factor out Utility.MonotonicClock

Utility/MonotonicClock.hs

@@ -0,0 +1,24 @@
+{- Monotonic clocks
+ -
+ - Copyright 2024 Joey Hess <id@joeyh.name>
+ -
+ - License: BSD-2-clause
+ -}
+
+{-# LANGUAGE CPP #-}
+
+module Utility.MonotonicClock where
+
+#if MIN_VERSION_clock(0,3,0)
+import qualified System.Clock as Clock
+#else
+import qualified System.Posix.Clock as Clock
+#endif
+
+newtype MonotonicTimestamp = MonotonicTimestamp Integer
+	deriving (Show, Eq, Ord)
+
+currentMonotonicTimestamp :: IO MonotonicTimestamp
+currentMonotonicTimestamp =
+	(MonotonicTimestamp . fromIntegral . Clock.sec)
+		<$> Clock.getTime Clock.Monotonic