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{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Crypto.Nonce
( Nonce32
, generateNonce32
, zeros32
) where
import Crypto.Random
import Data.ByteArray as BA
import Data.ByteString as B
import qualified Data.ByteString.Base64 as Base64
import Data.ByteString.Char8 as B8
import Data.Data
import Data.Serialize
import Data.Sized
newtype Nonce32 = Nonce32 ByteString
deriving (Eq, Ord, ByteArrayAccess, Data)
bin2base64 :: ByteArrayAccess bs => bs -> String
bin2base64 = B8.unpack . Base64.encode . BA.convert
instance Show Nonce32 where
showsPrec d nonce = mappend $ bin2base64 nonce
instance Read Nonce32 where
readsPrec _ str = either (const []) id $ do
let (ds,ss) = Prelude.splitAt 43 str
ss' <- case ss of
'=':xs -> Right xs -- optional terminating '='
_ -> Right ss
bs <- Base64.decode (B8.pack $ ds ++ ['='])
if B.length bs == 32
then Right [ (Nonce32 bs, ss') ]
else Left "Truncated Nonce32 (expected 43 base64 digits)."
instance Serialize Nonce32 where
get = Nonce32 <$> getBytes 32
put (Nonce32 bs) = putByteString bs
instance Sized Nonce32 where size = ConstSize 32
zeros32 :: Nonce32
zeros32 = Nonce32 $ BA.replicate 32 0
generateNonce32 :: MonadRandom m => m Nonce32
generateNonce32 = Nonce32 <$> getRandomBytes 32
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