46 lines
1.2 KiB
Haskell
46 lines
1.2 KiB
Haskell
{- git-annex vector clocks
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-
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- We don't have a way yet to keep true distributed vector clocks.
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- The next best thing is a timestamp.
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-
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- Copyright 2017 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Annex.VectorClock where
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import Data.Time.Clock.POSIX
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import Control.Applicative
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import Prelude
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import Utility.Env
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import Logs.TimeStamp
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import Utility.QuickCheck
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-- | Some very old logs did not have any time stamp at all;
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-- Unknown is used for those.
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data VectorClock = Unknown | VectorClock POSIXTime
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deriving (Eq, Ord)
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-- Unknown is oldest.
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prop_VectorClock_sane :: Bool
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prop_VectorClock_sane = Unknown < VectorClock 1
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instance Arbitrary VectorClock where
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arbitrary = VectorClock <$> arbitrary
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currentVectorClock :: IO VectorClock
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currentVectorClock = go =<< getEnv "GIT_ANNEX_VECTOR_CLOCK"
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where
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go Nothing = VectorClock <$> getPOSIXTime
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go (Just s) = case parsePOSIXTime s of
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Just t -> return (VectorClock t)
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Nothing -> VectorClock <$> getPOSIXTime
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formatVectorClock :: VectorClock -> String
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formatVectorClock Unknown = "0"
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formatVectorClock (VectorClock t) = show t
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parseVectorClock :: String -> Maybe VectorClock
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parseVectorClock t = VectorClock <$> parsePOSIXTime t
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