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|
{-# LANGUAGE TemplateHaskell #-}
module Network.BitTorrent.Exchange.Session.Metadata
( -- * Metadata transfer state
Status
, nullStatus
-- * Metadata updates
, Updates
, runUpdates
-- * Metadata piece control
, scheduleBlock
, resetPending
, cancelPending
, pushBlock
) where
import Control.Concurrent
import Control.Lens
import Control.Monad.Reader
import Control.Monad.State
import Data.ByteString as BS
import Data.ByteString.Lazy as BL
import Data.List as L
import Data.Tuple
import Data.BEncode as BE
import Data.Torrent
import Data.Torrent.InfoHash
import Data.Torrent.Piece as Torrent
import Network.BitTorrent.Core
import Network.BitTorrent.Exchange.Block as Block
import Network.BitTorrent.Exchange.Message as Message hiding (Status)
data Status = Status
{ _pending :: [(PeerAddr IP, PieceIx)]
, _bucket :: Bucket
}
makeLenses ''Status
-- | Create a new scheduler for infodict of the given size.
nullStatus :: Int -> Status
nullStatus ps = Status [] (Block.empty ps)
type Updates = ReaderT (PeerAddr IP) (State Status)
runUpdates :: MVar Status -> PeerAddr IP -> Updates a -> IO a
runUpdates v a m = modifyMVar v (return . swap . runState (runReaderT m a))
scheduleBlock :: Updates (Maybe PieceIx)
scheduleBlock = do
addr <- ask
bkt <- use bucket
case spans metadataPieceSize bkt of
[] -> return Nothing
((off, _ ) : _) -> do
let pix = off `div` metadataPieceSize
pending %= ((addr, pix) :)
return (Just pix)
cancelPending :: PieceIx -> Updates ()
cancelPending pix = pending %= L.filter ((pix ==) . snd)
resetPending :: Updates ()
resetPending = do
addr <- ask
pending %= L.filter ((addr ==) . fst)
parseInfoDict :: BS.ByteString -> InfoHash -> Result InfoDict
parseInfoDict chunk topic =
case BE.decode chunk of
Right (infodict @ InfoDict {..})
| topic == idInfoHash -> return infodict
| otherwise -> Left "broken infodict"
Left err -> Left $ "unable to parse infodict " ++ err
-- todo use incremental parsing to avoid BS.concat call
pushBlock :: Torrent.Piece BS.ByteString -> InfoHash -> Updates (Maybe InfoDict)
pushBlock Torrent.Piece {..} topic = do
addr <- ask
p <- use pending
when ((addr, pieceIndex) `L.notElem` p) $ error "not requested"
cancelPending pieceIndex
bucket %= Block.insert (metadataPieceSize * pieceIndex) pieceData
b <- use bucket
case toPiece b of
Nothing -> return Nothing
Just chunks ->
case parseInfoDict (BL.toStrict chunks) topic of
Right x -> do
pending .= []
return (Just x)
Left e -> do
pending .= []
bucket .= Block.empty (Block.size b)
return Nothing
|
