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diff --git a/src/Network/BitTorrent/PeerWire/Protocol.hs b/src/Network/BitTorrent/PeerWire/Protocol.hs
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+++ b/src/Network/BitTorrent/PeerWire/Protocol.hs
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+{-# LANGUAGE OverloadedStrings #-}
+module Network.BitTorrent.PeerWire.Protocol
+       (
+         -- * Messages
+         Message(..)
+       , ppMessage
+       ) where
+
+import Control.Applicative
+import qualified Data.ByteString as B
+import qualified Data.ByteString.Lazy as Lazy
+import Data.Serialize
+import Text.PrettyPrint
+import Network
+
+import Network.BitTorrent.PeerWire.Block
+import Data.Bitfield
+
+
+
+-- | Messages used in communication between peers.
+--
+--   Note: If some extensions are disabled (not present in extension
+--   mask) and client receive message used by the disabled
+--   extension then the client MUST close the connection.
+--
+data Message = KeepAlive
+             | Choke
+             | Unchoke
+             | Interested
+             | NotInterested
+
+               -- | Zero-based index of a piece that has just been
+               -- successfully downloaded and verified via the hash.
+             | Have     !PieceIx
+
+               -- | The bitfield message may only be sent immediately
+               -- after the handshaking sequence is complete, and
+               -- before any other message are sent. If client have no
+               -- pieces then bitfield need not to be sent.
+             | Bitfield !Bitfield
+
+               -- | Request for a particular block. If a client is
+               -- requested a block that another peer do not have the
+               -- peer might not answer at all.
+             | Request  !BlockIx
+
+               -- | Response for a request for a block.
+             | Piece    !Block
+
+               -- | Used to cancel block requests. It is typically
+               -- used during "End Game".
+             | Cancel   !BlockIx
+
+             | Port     !PortNumber
+
+               -- | BEP 6: Then peer have all pieces it might send the
+               --   'HaveAll' message instead of 'Bitfield'
+               --   message. Used to save bandwidth.
+             | HaveAll
+
+               -- | BEP 6: Then peer have no pieces it might send
+               -- 'HaveNone' message intead of 'Bitfield'
+               -- message. Used to save bandwidth.
+             | HaveNone
+
+               -- | BEP 6: This is an advisory message meaning "you
+               -- might like to download this piece." Used to avoid
+               -- excessive disk seeks and amount of IO.
+             | SuggestPiece !PieceIx
+
+               -- | BEP 6: Notifies a requesting peer that its request
+               -- will not be satisfied.
+             | RejectRequest !BlockIx
+
+               -- | BEP 6: This is an advisory messsage meaning "if
+               -- you ask for this piece, I'll give it to you even if
+               -- you're choked." Used to shorten starting phase.
+             | AllowedFast !PieceIx
+               deriving (Show, Eq)
+
+
+instance Serialize Message where
+  get = do
+    len <- getInt
+--    _   <- lookAhead $ ensure len
+    if len == 0 then return KeepAlive
+      else do
+        mid <- getWord8
+        case mid of
+          0x00 -> return Choke
+          0x01 -> return Unchoke
+          0x02 -> return Interested
+          0x03 -> return NotInterested
+          0x04 -> Have     <$> getInt
+          0x05 -> (Bitfield . fromBitmap) <$> getByteString (pred len)
+          0x06 -> Request  <$> get
+          0x07 -> Piece    <$> getBlock (len - 9)
+          0x08 -> Cancel   <$> get
+          0x09 -> (Port . fromIntegral) <$> getWord16be
+          0x0E -> return HaveAll
+          0x0F -> return HaveNone
+          0x0D -> SuggestPiece  <$> getInt
+          0x10 -> RejectRequest <$> get
+          0x11 -> AllowedFast   <$> getInt
+          _    -> do
+            rm <- remaining >>= getBytes
+            fail $ "unknown message ID: " ++ show mid ++ "\n"
+                ++ "remaining available bytes: " ++ show rm
+
+    where
+      getBlock :: Int -> Get Block
+      getBlock len = Block <$> getInt <*> getInt <*> getBytes len
+      {-# INLINE getBlock #-}
+
+
+  put KeepAlive     = putInt 0
+  put Choke         = putInt 1  >> putWord8 0x00
+  put Unchoke       = putInt 1  >> putWord8 0x01
+  put Interested    = putInt 1  >> putWord8 0x02
+  put NotInterested = putInt 1  >> putWord8 0x03
+  put (Have i)      = putInt 5  >> putWord8 0x04 >> putInt i
+  put (Bitfield bf) = putInt l  >> putWord8 0x05 >> putLazyByteString b
+    where b = toBitmap bf
+          l = succ (fromIntegral (Lazy.length b))
+          {-# INLINE l #-}
+  put (Request blk) = putInt 13 >> putWord8 0x06 >> put blk
+  put (Piece   blk) = putInt l  >> putWord8 0x07 >> putBlock
+    where l = 9 + B.length (blkData blk)
+          {-# INLINE l #-}
+          putBlock = do putInt (blkPiece blk)
+                        putInt (blkOffset  blk)
+                        putByteString (blkData blk)
+          {-# INLINE putBlock #-}
+
+  put (Cancel  blk)      = putInt 13 >> putWord8 0x08 >> put blk
+  put (Port    p  )      = putInt 3  >> putWord8 0x09 >> putWord16be (fromIntegral p)
+  put  HaveAll           = putInt 1  >> putWord8 0x0E
+  put  HaveNone          = putInt 1  >> putWord8 0x0F
+  put (SuggestPiece pix) = putInt 5  >> putWord8 0x0D >> putInt pix
+  put (RejectRequest ix) = putInt 13 >> putWord8 0x10 >> put ix
+  put (AllowedFast   ix) = putInt 5  >> putWord8 0x11 >> putInt ix
+
+
+-- | Format messages in human readable form. Note that output is
+--   compact and suitable for logging: only useful information but not
+--   payload bytes.
+--
+ppMessage :: Message -> Doc
+ppMessage (Bitfield _)       = "Bitfield"
+ppMessage (Piece blk)        = "Piece"    <+> ppBlock blk
+ppMessage (Cancel ix)        = "Cancel"   <+> ppBlockIx ix
+ppMessage (SuggestPiece pix) = "Suggest"  <+> int pix
+ppMessage (RejectRequest ix) = "Reject"   <+> ppBlockIx ix
+ppMessage msg = text (show msg)
\ No newline at end of file