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{- |
Module : Text.Pandoc.UUID
Copyright : Copyright (C) 2010-2020 John MacFarlane
License : GNU GPL, version 2 or above
Maintainer : John MacFarlane <jgm@berkeley.edu>
Stability : alpha
Portability : portable
UUID generation using Version 4 (random method) described
in RFC4122. See http://tools.ietf.org/html/rfc4122
-}
module Text.Pandoc.UUID ( UUID(..), getRandomUUID, getUUID ) where
import Data.Bits (clearBit, setBit)
import Data.Word
import System.Random (RandomGen, getStdGen, randoms)
import Text.Printf (printf)
data UUID = UUID Word8 Word8 Word8 Word8 Word8 Word8 Word8 Word8
Word8 Word8 Word8 Word8 Word8 Word8 Word8 Word8
instance Show UUID where
show (UUID a b c d e f g h i j k l m n o p) =
"urn:uuid:" ++
printf "%02x" a ++
printf "%02x" b ++
printf "%02x" c ++
printf "%02x" d ++
"-" ++
printf "%02x" e ++
printf "%02x" f ++
"-" ++
printf "%02x" g ++
printf "%02x" h ++
"-" ++
printf "%02x" i ++
printf "%02x" j ++
"-" ++
printf "%02x" k ++
printf "%02x" l ++
printf "%02x" m ++
printf "%02x" n ++
printf "%02x" o ++
printf "%02x" p
getUUID :: RandomGen g => g -> UUID
getUUID gen =
case take 16 (randoms gen :: [Word8]) of
[a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p] ->
-- set variant
let i' = i `setBit` 7 `clearBit` 6
-- set version (0100 for random)
g' = g `clearBit` 7 `setBit` 6 `clearBit` 5 `clearBit` 4
in UUID a b c d e f g' h i' j k l m n o p
_ -> error "not enough random numbers for UUID" -- should not happen
getRandomUUID :: IO UUID
getRandomUUID = getUUID <$> getStdGen
|
