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|
module Network.BitTorrent.Exchange.Session.Status
( -- * Environment
StatusUpdates
, runStatusUpdates
-- * Status
, SessionStatus
, sessionStatus
-- * Query
, getBitfield
, getRequestQueueLength
-- * Control
, scheduleBlocks
, resetPending
, pushBlock
) where
import Control.Applicative
import Control.Concurrent
import Control.Monad.State
import Data.ByteString.Lazy as BL
import Data.Default
import Data.List as L
import Data.Maybe
import Data.Map as M
import Data.Set as S
import Data.Tuple
import Data.Torrent.Piece
import Data.Torrent.Bitfield as BF
import Network.BitTorrent.Core
import Network.BitTorrent.Exchange.Block as Block
import System.Torrent.Storage (Storage, writePiece)
{-----------------------------------------------------------------------
-- Piece entry
-----------------------------------------------------------------------}
data PieceEntry = PieceEntry
{ pending :: [(PeerAddr IP, BlockIx)]
, stalled :: Bucket
}
pieceEntry :: PieceSize -> PieceEntry
pieceEntry s = PieceEntry [] (Block.empty s)
isEmpty :: PieceEntry -> Bool
isEmpty PieceEntry {..} = L.null pending && Block.null stalled
holes :: PieceIx -> PieceEntry -> [BlockIx]
holes pix PieceEntry {..} = fmap mkBlockIx (spans defaultTransferSize stalled)
where
mkBlockIx (off, sz) = BlockIx pix off sz
{-----------------------------------------------------------------------
-- Session status
-----------------------------------------------------------------------}
data SessionStatus = SessionStatus
{ inprogress :: !(Map PieceIx PieceEntry)
, bitfield :: !Bitfield
, pieceSize :: !PieceSize
}
sessionStatus :: Bitfield -> PieceSize -> SessionStatus
sessionStatus bf ps = SessionStatus
{ inprogress = M.empty
, bitfield = bf
, pieceSize = ps
}
type StatusUpdates a = StateT SessionStatus IO a
-- |
runStatusUpdates :: MVar SessionStatus -> StatusUpdates a -> IO a
runStatusUpdates var m = modifyMVar var (fmap swap . runStateT m)
getBitfield :: MVar SessionStatus -> IO Bitfield
getBitfield var = bitfield <$> readMVar var
getRequestQueueLength :: PeerAddr IP -> StatusUpdates Int
getRequestQueueLength addr = do
m <- gets (M.elems . M.map (L.filter ((==) addr . fst) . pending) . inprogress)
return $ L.sum $ L.map L.length m
modifyEntry :: PieceIx -> (PieceEntry -> PieceEntry) -> StatusUpdates ()
modifyEntry pix f = modify $ \ s @ SessionStatus {..} -> s
{ inprogress = alter (g pieceSize) pix inprogress }
where
g s = h . f . fromMaybe (pieceEntry s)
h e
| isEmpty e = Nothing
| otherwise = Just e
{-----------------------------------------------------------------------
-- Piece download
-----------------------------------------------------------------------}
-- TODO choose block nearest to pending or stalled sets to reduce disk
-- seeks on remote machines
chooseBlocks :: [BlockIx] -> Int -> StatusUpdates [BlockIx]
chooseBlocks xs n = return (L.take n xs)
-- TODO use selection strategies from Exchange.Selector
choosePiece :: Bitfield -> StatusUpdates (Maybe PieceIx)
choosePiece bf
| BF.null bf = return $ Nothing
| otherwise = return $ Just $ BF.findMin bf
scheduleBlocks :: PeerAddr IP -> Bitfield -> Int -> StatusUpdates [BlockIx]
scheduleBlocks addr maskBF n = do
SessionStatus {..} <- get
let wantPieces = maskBF `BF.difference` bitfield
let wantBlocks = L.concat $ M.elems $ M.mapWithKey holes $
M.filterWithKey (\ pix _ -> pix `BF.member` wantPieces) inprogress
bixs <- if L.null wantBlocks
then do
mpix <- choosePiece wantPieces
case mpix of -- TODO return 'n' blocks
Nothing -> return []
Just pix -> return [leadingBlock pix defaultTransferSize]
else chooseBlocks wantBlocks n
forM_ bixs $ \ bix -> do
modifyEntry (ixPiece bix) $ \ e @ PieceEntry {..} -> e
{ pending = (addr, bix) : pending }
return bixs
-- | Remove all pending block requests to the remote peer. May be used
-- when:
--
-- * a peer closes connection;
--
-- * remote peer choked this peer;
--
-- * timeout expired.
--
resetPending :: PeerAddr IP -> StatusUpdates ()
resetPending addr = modify $ \ s -> s { inprogress = reset (inprogress s) }
where
reset = fmap $ \ e -> e
{ pending = L.filter (not . (==) addr . fst) (pending e) }
-- | MAY write to storage, if a new piece have been completed.
pushBlock :: Block BL.ByteString -> Storage -> StatusUpdates (Maybe Bool)
pushBlock blk @ Block {..} storage = do
mpe <- gets (M.lookup blkPiece . inprogress)
case mpe of
Nothing -> return Nothing
Just (pe @ PieceEntry {..})
| blockIx blk `L.notElem` fmap snd pending -> return Nothing
| otherwise -> do
let bkt' = Block.insertLazy blkOffset blkData stalled
case toPiece bkt' of
Nothing -> do
modifyEntry blkPiece $ \ e @ PieceEntry {..} -> e
{ pending = L.filter ((==) (blockIx blk) . snd) pending
, stalled = bkt'
}
return (Just False)
Just pieceData -> do
-- TODO verify
liftIO $ writePiece (Piece blkPiece pieceData) storage
modify $ \ s @ SessionStatus {..} -> s
{ inprogress = M.delete blkPiece inprogress
, bitfield = BF.insert blkPiece bitfield
}
return (Just True)
|
