+ Add some bitfield operations.

1 files changed, 82 insertions, 6 deletions

diff --git a/src/Network/BitTorrent/PeerWire/Bitfield.hs b/src/Network/BitTorrent/PeerWire/Bitfield.hs
index c9357a25..5cbd4e86 100644
--- a/src/Network/BitTorrent/PeerWire/Bitfield.hs
+++ b/src/Network/BitTorrent/PeerWire/Bitfield.hs
@@ -12,23 +12,95 @@
 --
 module Network.BitTorrent.PeerWire.Bitfield
        ( Bitfield(..)
+
+         -- * Construction
+       , empty, full
+       , fromByteString, toByteString
+
+         -- * Query
+       , findMin, findMax, difference
+
+         -- * Serialization
        , getBitfield, putBitfield, bitfieldByteCount
        ) where
 
-import Control.Applicative
+import Control.Applicative hiding (empty)
+import Data.Array.Unboxed
+import Data.Bits
 import           Data.ByteString (ByteString)
 import qualified Data.ByteString as B
-
+import Data.List as L
+import Data.Maybe
 import Data.Serialize
+import Data.Word
 
+import Network.BitTorrent.PeerWire.Block
+import Data.Torrent
 
 newtype Bitfield = MkBitfield {
     bfBits :: ByteString
+--  , bfSize :: Int
   } deriving (Show, Eq, Ord)
 
-bitfieldByteCount :: Bitfield -> Int
-bitfieldByteCount = B.length . bfBits
-{-# INLINE bitfieldByteCount #-}
+
+empty :: Int -> Bitfield
+empty n = MkBitfield $ B.replicate (sizeInBase n 8) 0
+
+full :: Int -> Bitfield
+full n = MkBitfield $ B.replicate (sizeInBase n 8)  (complement 0)
+
+fromByteString :: ByteString -> Bitfield
+fromByteString = MkBitfield
+{-# INLINE fromByteString #-}
+
+toByteString :: Bitfield -> ByteString
+toByteString = bfBits
+{-# INLINE toByteString #-}
+
+combine :: [ByteString] -> Maybe ByteString
+combine []         = Nothing
+combine as@(a : _) = return $ foldr andBS empty as
+  where
+    andBS x acc = B.pack (B.zipWith (.&.) x acc)
+    empty = B.replicate (B.length a) 0
+
+frequencies :: [Bitfield] -> UArray PieceIx Int
+frequencies = undefined
+
+diffWord8 :: Word8 -> Word8 -> Word8
+diffWord8 a b = a .&. (a `xor` b)
+{-# INLINE diffWord8 #-}
+
+difference :: Bitfield -> Bitfield -> Bitfield
+difference a b = MkBitfield $ B.pack $ B.zipWith diffWord8 (bfBits a) (bfBits b)
+{-# INLINE difference #-}
+
+difference' :: ByteString -> ByteString -> ByteString
+difference' a b = undefined
+  where
+    go i = undefined
+
+
+-- TODO: bit tricks
+findMinWord8 :: Word8 -> Maybe Int
+findMinWord8 b = L.findIndex (testBit b) [0..bitSize (undefined :: Word8) - 1]
+{-# INLINE findMinWord8 #-}
+
+-- | Get min index of piece that the peer have.
+findMin :: Bitfield -> Maybe PieceIx
+findMin (MkBitfield b) = do
+  byteIx <- B.findIndex (0 /=) b
+  bitIx  <- findMinWord8 (B.index b byteIx)
+  return $ byteIx * bitSize (undefined :: Word8) + bitIx
+{-# INLINE findMin #-}
+
+findMaxWord8 :: Word8 -> Maybe Int
+findMaxWord8 = error "bitfield: findMaxWord8"
+
+findMax :: Bitfield -> Maybe PieceIx
+findMax = error "bitfield: findMax"
+{-# INLINE findMax #-}
+
 
 getBitfield :: Int -> Get Bitfield
 getBitfield n = MkBitfield <$> getBytes n
@@ -36,4 +108,8 @@ getBitfield n = MkBitfield <$> getBytes n
 
 putBitfield :: Bitfield -> Put
 putBitfield = putByteString . bfBits
-{-# INLINE putBitfield #-}
\ No newline at end of file
+{-# INLINE putBitfield #-}
+
+bitfieldByteCount :: Bitfield -> Int
+bitfieldByteCount = B.length . bfBits
+{-# INLINE bitfieldByteCount #-}