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|
-- |
-- 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 #-}
|
