4 files changed, 52 insertions, 10 deletions

diff --git a/network-bittorrent.cabal b/network-bittorrent.cabal
index 5cd46216..8c6fd84d 100644
--- a/network-bittorrent.cabal
+++ b/network-bittorrent.cabal
@@ -57,6 +57,7 @@ library
                      , HTTP       >= 4000.2
                      , cryptohash
 
+                     , filepath   == 1.*
 
   extensions:          PatternGuards
   hs-source-dirs:      src
diff --git a/src/Data/Torrent.hs b/src/Data/Torrent.hs
index e6ed8813..226126f2 100644
--- a/src/Data/Torrent.hs
+++ b/src/Data/Torrent.hs
@@ -11,7 +11,8 @@
 module Data.Torrent
        ( module Data.Torrent.InfoHash
        , Torrent(..), ContentInfo(..), FileInfo(..)
-       , contenLength, pieceCount
+       , contentLength, pieceCount
+       , contentLayout
        , fromFile
        ) where
 
@@ -24,7 +25,7 @@ import           Data.Text (Text)
 import Data.BEncode
 import Data.Torrent.InfoHash
 import Network.URI
-
+import System.FilePath
 
 type Time = Text
 
@@ -229,6 +230,26 @@ contentLength MultiFile  { ciFiles  = tfs } = sum (map fiLength tfs)
 pieceCount :: ContentInfo -> Int
 pieceCount ti = contentLength ti `sizeInBase` ciPieceLength ti
 
+-- | File layout specifies the order and the size of each file in the storage.
+--   Note that order of files is highly important since we coalesce all
+--   the files in the given order to get the linear block address space.
+--
+type Layout = [(FilePath, Int)]
+
+fileInfo :: ContentInfo -> [FileInfo]
+fileInfo  (SingleFile { ciName = name, ciLength = len, ciMD5sum = md5 })
+  = [FileInfo len md5 [name]]
+fileInfo  (MultiFile  { ciFiles = fs }) = fs
+
+fileLayout :: FileInfo -> (FilePath, Int)
+fileLayout (FileInfo { fiLength = len, fiPath = name }) = (path, fromIntegral len)
+  where   -- WARN use utf8 encoding in name
+    path = joinPath (map BC.unpack name)
+
+
+contentLayout :: ContentInfo -> Layout
+contentLayout = map fileLayout . fileInfo
+
 
 -- | Read and decode a .torrent file.
 fromFile :: FilePath -> IO (Result Torrent)
diff --git a/src/Network/BitTorrent/PeerWire/Block.hs b/src/Network/BitTorrent/PeerWire/Block.hs
index 33e3dead..a5bc4f32 100644
--- a/src/Network/BitTorrent/PeerWire/Block.hs
+++ b/src/Network/BitTorrent/PeerWire/Block.hs
@@ -1,25 +1,41 @@
 module Network.BitTorrent.PeerWire.Block
        ( BlockIx(..), Block(..)
+       , BlockLIx, PieceLIx
        , defaultBlockSize
-       , blockRange, ixRange, pieceIx
-       , isPiece
+       , pieceIx, blockIx
+       , blockRange, ixRange, isPiece
        ) where
 
+import Control.Applicative
 import           Data.ByteString (ByteString)
 import qualified Data.ByteString as B
 import Data.Int
 
+type BlockLIx = Int
+type PieceLIx = Int
+
 
 data BlockIx = BlockIx {
-    ixPiece  :: {-# UNPACK #-} !Int -- ^ Zero-based piece index.
-  , ixOffset :: {-# UNPACK #-} !Int -- ^ Zero-based byte offset within the piece.
-  , ixLength :: {-# UNPACK #-} !Int -- ^ Block size starting from offset.
+    -- ^ Zero-based piece index.
+    ixPiece  :: {-# UNPACK #-} !PieceLIx
+
+    -- ^ Zero-based byte offset within the piece.
+  , ixOffset :: {-# UNPACK #-} !Int
+
+    -- ^ Block size starting from offset.
+  , ixLength :: {-# UNPACK #-} !Int
   } deriving (Show, Eq)
 
+
 data Block = Block {
-    blkPiece  :: Int         -- ^ Zero-based piece index.
-  , blkOffset :: Int         -- ^ Zero-based byte offset within the piece.
-  , blkData   :: ByteString  -- ^ Payload.
+    -- ^ Zero-based piece index.
+    blkPiece  :: PieceLIx
+
+    -- ^ Zero-based byte offset within the piece.
+  , blkOffset :: Int
+
+    -- ^ Payload.
+  , blkData   :: ByteString
   } deriving (Show, Eq)
 
 
@@ -37,6 +53,9 @@ pieceIx :: Int -> Int -> BlockIx
 pieceIx i = BlockIx i 0
 {-# INLINE pieceIx #-}
 
+blockIx :: Block -> BlockIx
+blockIx = BlockIx <$> blkPiece <*> blkOffset <*> B.length . blkData
+
 blockRange :: (Num a, Integral a) => Int -> Block -> (a, a)
 blockRange pieceSize blk = (offset, offset + len)
   where
diff --git a/src/Network/BitTorrent/Tracker.hs b/src/Network/BitTorrent/Tracker.hs
index 4275e5fe..643aca16 100644
--- a/src/Network/BitTorrent/Tracker.hs
+++ b/src/Network/BitTorrent/Tracker.hs
@@ -8,6 +8,7 @@
 --
 {-# OPTIONS -fno-warn-orphans #-}
 {-# LANGUAGE OverloadedStrings #-}
+-- make higher level api
 module Network.BitTorrent.Tracker
        ( module Network.BitTorrent.Tracker.Scrape
        , Progress(..), TSession(..)