1 files changed, 17 insertions, 1 deletions

diff --git a/src/Network/BitTorrent/DHT/Token.hs b/src/Network/BitTorrent/DHT/Token.hs
index 08079b75..756b5a98 100644
--- a/src/Network/BitTorrent/DHT/Token.hs
+++ b/src/Network/BitTorrent/DHT/Token.hs
@@ -21,6 +21,9 @@
 module Network.BitTorrent.DHT.Token
        ( -- * Token
          Token
+       , maxInterval
+       , toPaddedByteString
+       , fromPaddedByteString
 
          -- * Session tokens
        , TokenMap
@@ -74,7 +77,19 @@ instance Show Token where
 
 -- | Meaningless token, for testing purposes only.
 instance Default Token where
-  def = Token "0xdeadbeef"
+  def = makeToken (0::Int) 0
+
+-- | Prepend token with 0x20 bytes to fill the available width.
+--
+-- If n > 8, then this will also guarantee a nonzero token, which is useful for
+-- Tox ping-id values for announce responses.
+toPaddedByteString :: Int -> Token -> BS.ByteString
+toPaddedByteString n (Token bs) = BS.append (BS.replicate (n - BS.length bs) 0x20) bs
+
+fromPaddedByteString :: Int -> BS.ByteString -> Token
+fromPaddedByteString n bs = Token $ BS.drop (n - len) bs
+ where
+    len = BS.length tok where Token tok = def
 
 -- | The secret value used as salt.
 type Secret = Int
@@ -85,6 +100,7 @@ makeToken :: Hashable a => a -> Secret -> Token
 makeToken n s = Token $ toBS $ hashWithSalt s n
   where
     toBS = toStrict . toLazyByteString . int64BE . fromIntegral
+{-# INLINE makeToken #-}
 
 -- | Constant space 'Node' to 'Token' map based on the secret value.
 data TokenMap = TokenMap