git.iko.soy/typeable/pandoc
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typeable/pandoc/src/Text/Pandoc/UUID.hs
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1{- |
2 Module : Text.Pandoc.UUID
3 Copyright : Copyright (C) 2010-2020 John MacFarlane
4 License : GNU GPL, version 2 or above
6 Maintainer : John MacFarlane <jgm@berkeley.edu>
7 Stability : alpha
8 Portability : portable
10UUID generation using Version 4 (random method) described
11in RFC4122. See http://tools.ietf.org/html/rfc4122
12-}
14module Text.Pandoc.UUID ( UUID(..), getRandomUUID ) where
16import Data.Bits (clearBit, setBit)
17import Data.Word
18import System.Random (RandomGen, randoms)
19import Text.Printf (printf)
20import Text.Pandoc.Class.PandocMonad
22data UUID = UUID Word8 Word8 Word8 Word8 Word8 Word8 Word8 Word8
23 Word8 Word8 Word8 Word8 Word8 Word8 Word8 Word8
25instance Show UUID where
26 show (UUID a b c d e f g h i j k l m n o p) =
27 "urn:uuid:" ++
28 printf "%02x" a ++
29 printf "%02x" b ++
30 printf "%02x" c ++
31 printf "%02x" d ++
32 "-" ++
33 printf "%02x" e ++
34 printf "%02x" f ++
35 "-" ++
36 printf "%02x" g ++
37 printf "%02x" h ++
38 "-" ++
39 printf "%02x" i ++
40 printf "%02x" j ++
41 "-" ++
42 printf "%02x" k ++
43 printf "%02x" l ++
44 printf "%02x" m ++
45 printf "%02x" n ++
46 printf "%02x" o ++
47 printf "%02x" p
49getUUID :: RandomGen g => g -> UUID
50getUUID gen =
51 case take 16 (randoms gen :: [Word8]) of
52 [a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p] ->
53 -- set variant
54 let i' = i `setBit` 7 `clearBit` 6
55 -- set version (0100 for random)
56 g' = g `clearBit` 7 `setBit` 6 `clearBit` 5 `clearBit` 4
57 in UUID a b c d e f g' h i' j k l m n o p
58 _ -> error "not enough random numbers for UUID" -- should not happen
60getRandomUUID :: PandocMonad m => m UUID
61getRandomUUID = getUUID <$> newStdGen