2 files changed, 164 insertions, 1 deletions

diff --git a/src/Network/BitTorrent/Exchange/Block.hs b/src/Network/BitTorrent/Exchange/Block.hs
new file mode 100644
index 00000000..e99dd49d
--- /dev/null
+++ b/src/Network/BitTorrent/Exchange/Block.hs
@@ -0,0 +1,163 @@
+-- |
+--   Copyright   :  (c) Sam Truzjan 2013
+--   License     :  BSD3
+--   Maintainer  :  pxqr.sta@gmail.com
+--   Stability   :  experimental
+--   Portability :  portable
+--
+--   Blocks are used to transfer pieces.
+--
+{-# LANGUAGE FlexibleInstances          #-}
+{-# LANGUAGE TemplateHaskell            #-}
+{-# LANGUAGE DeriveFunctor              #-}
+{-# LANGUAGE DeriveDataTypeable         #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module Network.BitTorrent.Exchange.Block
+       ( -- * Block attributes
+         BlockOffset
+       , BlockCount
+       , BlockSize
+       , defaultTransferSize
+
+         -- * Block index
+       , BlockIx(..)
+       , blockIxRange
+
+         -- * Block data
+       , Block(..)
+       , blockIx
+       , blockSize
+       , blockRange
+       , isPiece
+       ) where
+
+import Control.Applicative
+import Data.Aeson.TH
+import qualified Data.ByteString.Lazy as Lazy
+import Data.Char
+import Data.List as L
+import Data.Serialize as S
+import Data.Typeable
+import Text.PrettyPrint
+import Text.PrettyPrint.Class
+
+import Data.Torrent.Piece
+
+{-----------------------------------------------------------------------
+--  Block attributes
+-----------------------------------------------------------------------}
+
+-- | Offset of a block in a piece in bytes. Should be multiple of
+-- the choosen block size.
+type BlockOffset = Int
+
+-- | Size of a block in bytes. Should be power of 2.
+--
+--   Normally block size is equal to 'defaultTransferSize'.
+--
+type BlockSize   = Int
+
+-- | Number of block in a piece of a torrent. Used to distinguish
+-- block count from piece count.
+type BlockCount  = Int
+
+-- | Widely used semi-official block size. Some clients can ignore if
+-- block size of BlockIx in Request message is not equal to this
+-- value.
+--
+defaultTransferSize :: BlockSize
+defaultTransferSize = 16 * 1024
+
+{-----------------------------------------------------------------------
+    Block Index
+-----------------------------------------------------------------------}
+
+-- | BlockIx correspond.
+data BlockIx = BlockIx {
+    -- | Zero-based piece index.
+    ixPiece  :: {-# UNPACK #-} !PieceIx
+
+    -- | Zero-based byte offset within the piece.
+  , ixOffset :: {-# UNPACK #-} !BlockOffset
+
+    -- | Block size starting from offset.
+  , ixLength :: {-# UNPACK #-} !BlockSize
+  } deriving (Show, Eq, Typeable)
+
+$(deriveJSON defaultOptions { fieldLabelModifier = (L.map toLower . L.dropWhile isLower) } ''BlockIx)
+
+getInt :: S.Get Int
+getInt = fromIntegral <$> S.getWord32be
+{-# INLINE getInt #-}
+
+putInt :: S.Putter Int
+putInt = S.putWord32be . fromIntegral
+{-# INLINE putInt #-}
+
+instance Serialize BlockIx where
+  {-# SPECIALIZE instance Serialize BlockIx #-}
+  get = BlockIx <$> getInt
+                <*> getInt
+                <*> getInt
+  {-# INLINE get #-}
+
+  put BlockIx {..} = do
+    putInt ixPiece
+    putInt ixOffset
+    putInt ixLength
+  {-# INLINE put #-}
+
+instance Pretty BlockIx where
+  pretty BlockIx {..} =
+    "piece  = " <> int ixPiece  <> "," <+>
+    "offset = " <> int ixOffset <> "," <+>
+    "length = " <> int ixLength
+
+-- | Get location of payload bytes in the torrent content.
+blockIxRange :: (Num a, Integral a) => PieceSize -> BlockIx -> (a, a)
+blockIxRange pieceSize BlockIx {..} = (offset, offset + len)
+  where
+    offset = fromIntegral  pieceSize * fromIntegral ixPiece
+           + fromIntegral ixOffset
+    len    = fromIntegral ixLength
+{-# INLINE blockIxRange #-}
+
+{-----------------------------------------------------------------------
+    Block
+-----------------------------------------------------------------------}
+
+data Block payload = Block {
+    -- | Zero-based piece index.
+    blkPiece  :: {-# UNPACK #-} !PieceIx
+
+    -- | Zero-based byte offset within the piece.
+  , blkOffset :: {-# UNPACK #-} !BlockOffset
+
+    -- | Payload bytes.
+  , blkData   :: !payload
+  } deriving (Show, Eq, Functor, Typeable)
+
+-- | Payload is ommitted.
+instance Pretty (Block Lazy.ByteString) where
+  pretty = pretty . blockIx
+  {-# INLINE pretty #-}
+
+-- | Get size of block /payload/ in bytes.
+blockSize :: Block Lazy.ByteString -> BlockSize
+blockSize blk = fromIntegral (Lazy.length (blkData blk))
+{-# INLINE blockSize #-}
+
+-- | Get block index of a block.
+blockIx :: Block Lazy.ByteString -> BlockIx
+blockIx = BlockIx <$> blkPiece <*> blkOffset <*> blockSize
+
+-- | Get location of payload bytes in the torrent content.
+blockRange :: (Num a, Integral a) => PieceSize -> Block Lazy.ByteString -> (a, a)
+blockRange pieceSize = blockIxRange pieceSize . blockIx
+{-# INLINE blockRange #-}
+
+-- | Test if a block can be safely turned into a piece.
+isPiece :: PieceSize -> Block Lazy.ByteString -> Bool
+isPiece pieceLen blk @ (Block i offset _) =
+     offset == 0 && blockSize blk == pieceLen && i >= 0
+{-# INLINE isPiece #-}
diff --git a/src/Network/BitTorrent/Exchange/Message.hs b/src/Network/BitTorrent/Exchange/Message.hs
index 2f85d729..8a88b761 100644
--- a/src/Network/BitTorrent/Exchange/Message.hs
+++ b/src/Network/BitTorrent/Exchange/Message.hs
@@ -90,10 +90,10 @@ import Text.PrettyPrint as PP
 import Text.PrettyPrint.Class
 
 import Data.Torrent.Bitfield
-import Data.Torrent.Block
 import Data.Torrent.InfoHash
 import Network.BitTorrent.Core.PeerId
 import Network.BitTorrent.Core.PeerAddr ()
+import Network.BitTorrent.Exchange.Block
 
 {-----------------------------------------------------------------------
 --  Extensions