72 lines
2 KiB
Haskell
72 lines
2 KiB
Haskell
{- timestamp parsing and formatting
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-
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- Copyright 2015-2023 Joey Hess <id@joeyh.name>
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-
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- License: BSD-2-clause
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-}
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{-# LANGUAGE CPP #-}
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module Utility.TimeStamp (
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parserPOSIXTime,
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parsePOSIXTime,
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formatPOSIXTime,
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truncateResolution,
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) where
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import Utility.Data
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import Data.Time.Clock.POSIX
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import Data.Time
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import Data.Ratio
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import Control.Applicative
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import qualified Data.ByteString as B
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import qualified Data.ByteString.Char8 as B8
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import qualified Data.Attoparsec.ByteString as A
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import Data.Attoparsec.ByteString.Char8 (char, decimal, signed, isDigit_w8)
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{- Parses how POSIXTime shows itself: "1431286201.113452s"
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- (The "s" is included for historical reasons and is optional.)
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- Also handles the format with no decimal seconds. -}
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parserPOSIXTime :: A.Parser POSIXTime
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parserPOSIXTime = mkPOSIXTime
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<$> signed decimal
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<*> (declen <|> pure (0, 0))
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<* optional (char 's')
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where
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declen :: A.Parser (Integer, Int)
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declen = do
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_ <- char '.'
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b <- A.takeWhile isDigit_w8
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let len = B.length b
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d <- either fail pure $
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A.parseOnly (decimal <* A.endOfInput) b
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return (d, len)
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parsePOSIXTime :: String -> Maybe POSIXTime
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parsePOSIXTime s = eitherToMaybe $
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A.parseOnly (parserPOSIXTime <* A.endOfInput) (B8.pack s)
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{- This implementation allows for higher precision in a POSIXTime than
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- supported by the system's Double, and avoids the complications of
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- floating point. -}
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mkPOSIXTime :: Integer -> (Integer, Int) -> POSIXTime
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mkPOSIXTime n (d, dlen)
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| n < 0 = fromIntegral n - fromRational r
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| otherwise = fromIntegral n + fromRational r
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where
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r = d % (10 ^ dlen)
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formatPOSIXTime :: String -> POSIXTime -> String
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formatPOSIXTime fmt t = formatTime defaultTimeLocale fmt (posixSecondsToUTCTime t)
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{- Truncate the resolution to the specified number of decimal places. -}
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truncateResolution :: Int -> POSIXTime -> POSIXTime
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#if MIN_VERSION_time(1,9,1)
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truncateResolution n t = secondsToNominalDiffTime $
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fromIntegral ((truncate (nominalDiffTimeToSeconds t * d)) :: Integer) / d
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where
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d = 10 ^ n
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#else
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truncateResolution _ t = t
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#endif
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