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1+{-# OPTIONS_GHC -fno-cse #-}
2+{-# LANGUAGE TypeFamilies #-}
3+
4+{- |
5+Module : Data.UUID.V1
6+Copyright : (c) 2008 Jason Dusek
7+ (c) 2009 Mark Lentczner
8+ (c) 2009-2010,2012 Antoine Latter
9+
10+License : BSD-style
11+
12+Maintainer : aslatter@gmail.com
13+Stability : experimental
14+Portability : portable
15+
16+RFC 4122 Version 1 UUID state machine.
17+
18+The generated UUID is based on the hardware MAC
19+address and the system clock.
20+
21+If we cannot lookup the MAC address we seed the
22+generator with a pseudo-random number.
23+-}
24+
25+module Data.UUID.V1(nextUUID)
26+where
27+
28+
29+import Data.Bits
30+import Data.Maybe
31+import Data.Time
32+import Data.Word
33+
34+import Control.Applicative ((<$>),(<*>))
35+import Control.Concurrent.MVar
36+import System.IO.Unsafe
37+
38+import qualified System.Random as R
39+
40+import Network.Info
41+
42+import Data.UUID.Types.Internal.Builder
43+import Data.UUID.Types.Internal
44+
45+-- | Returns a new UUID derived from the local hardware MAC
46+-- address and the current system time.
47+-- Is generated according to the Version 1 UUID specified in
48+-- RFC 4122.
49+--
50+-- Returns 'Nothing' if you request UUIDs too quickly.
51+nextUUID :: IO (Maybe UUID)
52+nextUUID = do
53+ res <- stepTime
54+ case res of
55+ Just (mac', c, t) -> return $ Just $ makeUUID t c mac'
56+ _ -> return Nothing
57+
58+
59+makeUUID :: Word64 -> Word16 -> MAC -> UUID
60+makeUUID time clock mac' =
61+ buildFromBytes 1 /-/ tLow /-/ tMid /-/ tHigh /-/ clock /-/ (MACSource mac')
62+ where tLow = (fromIntegral time) :: Word32
63+ tMid = (fromIntegral (time `shiftR` 32)) :: Word16
64+ tHigh = (fromIntegral (time `shiftR` 48)) :: Word16
65+
66+newtype MACSource = MACSource MAC
67+instance ByteSource MACSource where
68+ z /-/ (MACSource (MAC a b c d e f)) = z a b c d e f
69+type instance ByteSink MACSource g = Takes3Bytes (Takes3Bytes g)
70+
71+
72+-- |Approximates the clock algorithm in RFC 4122, section 4.2
73+-- Isn't system wide or thread safe, nor does it properly randomize
74+-- the clock value on initialization.
75+stepTime :: IO (Maybe (MAC, Word16, Word64))
76+stepTime = do
77+ h1 <- fmap hundredsOfNanosSinceGregorianReform getCurrentTime
78+ modifyMVar state $ \s@(State mac' c0 h0) ->
79+ if h1 > h0
80+ then
81+ return (State mac' c0 h1, Just (mac', c0, h1))
82+ else
83+ let
84+ c1 = succ c0
85+ in if c1 <= 0x3fff -- when clock is initially randomized,
86+ -- then this test will need to change
87+ then
88+ return (State mac' c1 h1, Just (mac', c1, h1))
89+ else
90+ return (s, Nothing)
91+
92+
93+{-# NOINLINE state #-}
94+state :: MVar State
95+state = unsafePerformIO $ do
96+ h0 <- fmap hundredsOfNanosSinceGregorianReform getCurrentTime
97+ mac' <- getMac
98+ newMVar $ State mac' 0 h0 -- the 0 should be a random number
99+
100+-- SysMAC.mac can fail on some machines.
101+-- In those cases we fake it with a random
102+-- 6 bytes seed.
103+getMac :: IO MAC
104+getMac =
105+ getNetworkInterfaces >>=
106+ return . listToMaybe . filter (minBound /=) . map mac >>=
107+ \macM -> case macM of
108+ Just m -> return m
109+ Nothing -> randomMac
110+
111+randomMac :: IO MAC
112+randomMac =
113+ -- I'm too lazy to thread through
114+ -- the random state ...
115+ MAC
116+ <$> (R.randomIO >>= return . (1 .|.)) -- We must set the multicast bit to True. See section 4.5 of the RFC.
117+ <*> R.randomIO
118+ <*> R.randomIO
119+ <*> R.randomIO
120+ <*> R.randomIO
121+ <*> R.randomIO
122+
123+data State = State
124+ {-# UNPACK #-} !MAC
125+ {-# UNPACK #-} !Word16
126+ {-# UNPACK #-} !Word64
127+ deriving (Show)
128+
129+
130+
131+hundredsOfNanosSinceGregorianReform :: UTCTime -> Word64
132+hundredsOfNanosSinceGregorianReform t = floor $ 10000000 * dt
133+ where
134+ gregorianReform = UTCTime (fromGregorian 1582 10 15) 0
135+ dt = t `diffUTCTime` gregorianReform