{-# LANGUAGE NoImplicitPrelude #-} {- Copyright (C) 2010-2018 John MacFarlane <jgm@berkeley.edu> This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA -} {- | Module : Text.Pandoc.UUID Copyright : Copyright (C) 2010-2018 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 Prelude 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