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|
{- timestamp parsing and formatting
-
- Copyright 2015-2019 Joey Hess <id@joeyh.name>
-
- License: BSD-2-clause
-}
module Utility.TimeStamp (
parserPOSIXTime,
parsePOSIXTime,
formatPOSIXTime,
) where
import Utility.Data
import Data.Time.Clock.POSIX
import Data.Time
import Data.Ratio
import Control.Applicative
import qualified Data.ByteString as B
import qualified Data.ByteString.Char8 as B8
import qualified Data.Attoparsec.ByteString as A
import Data.Attoparsec.ByteString.Char8 (char, decimal, signed, isDigit_w8)
{- Parses how POSIXTime shows itself: "1431286201.113452s"
- (The "s" is included for historical reasons and is optional.)
- Also handles the format with no decimal seconds. -}
parserPOSIXTime :: A.Parser POSIXTime
parserPOSIXTime = mkPOSIXTime
<$> signed decimal
<*> (declen <|> pure (0, 0))
<* optional (char 's')
where
declen :: A.Parser (Integer, Int)
declen = do
_ <- char '.'
b <- A.takeWhile isDigit_w8
let len = B.length b
d <- either fail pure $
A.parseOnly (decimal <* A.endOfInput) b
return (d, len)
parsePOSIXTime :: String -> Maybe POSIXTime
parsePOSIXTime s = eitherToMaybe $
A.parseOnly (parserPOSIXTime <* A.endOfInput) (B8.pack s)
{- This implementation allows for higher precision in a POSIXTime than
- supported by the system's Double, and avoids the complications of
- floating point. -}
mkPOSIXTime :: Integer -> (Integer, Int) -> POSIXTime
mkPOSIXTime n (d, dlen)
| n < 0 = fromIntegral n - fromRational r
| otherwise = fromIntegral n + fromRational r
where
r = d % (10 ^ dlen)
formatPOSIXTime :: String -> POSIXTime -> String
formatPOSIXTime fmt t = formatTime defaultTimeLocale fmt (posixSecondsToUTCTime t)
|
