New storage

4 files changed, 193 insertions, 523 deletions

diff --git a/src/Data/Torrent/Layout.hs b/src/Data/Torrent/Layout.hs
index c1e26d48..7ed8679d 100644
--- a/src/Data/Torrent/Layout.hs
+++ b/src/Data/Torrent/Layout.hs
@@ -52,7 +52,7 @@ module Data.Torrent.Layout
          -- * Flat file layout
        , FileLayout
        , flatLayout
-       , accumOffsets
+       , accumPositions
        , fileOffset
 
          -- * Internal
@@ -303,11 +303,11 @@ flatLayout prefixPath MultiFile  {..}     = L.map mkPath liFiles
            </> joinPath (L.map BC.unpack fiName)
 
 -- | Calculate offset of each file based on its length, incrementally.
-accumOffsets :: FileLayout FileSize -> FileLayout FileOffset
-accumOffsets = go 0
+accumPositions :: FileLayout FileSize -> FileLayout (FileOffset, FileSize)
+accumPositions = go 0
   where
     go !_ [] = []
-    go !offset ((n, s) : xs) = (n, offset) : go (offset + s) xs
+    go !offset ((n, s) : xs) = (n, (offset, s)) : go (offset + s) xs
 
 -- | Gives global offset of a content file for a given full path.
 fileOffset :: FilePath -> FileLayout FileOffset -> Maybe FileOffset
diff --git a/src/System/IO/MMap/Fixed.hs b/src/System/IO/MMap/Fixed.hs
deleted file mode 100644
index 1e83c350..00000000
--- a/src/System/IO/MMap/Fixed.hs
+++ /dev/null
@@ -1,212 +0,0 @@
--- TODO pprint
--- TODO see if this IntervalMap is overkill: Interval dataty have 4 constrs
--- TODO clarify lifetime in docs
--- TODO use madvise
--- TODO unmap selected interval
--- TODO tests
--- TODO benchmarks
--- TODO unmap overlapped regions
--- [A] TODO lazy mapping for 32 bit arch;
---          we need tricky algorithm and a lot of perf tests
--- TODO use memmove in write bytes
--- TODO write elem, write byte, read byte
--- |
---   Copyright   :  (c) Sam T. 2013
---   License     :  MIT
---   Maintainer  :  pxqr.sta@gmail.com
---   Stability   :  experimental
---   Portability :  portable
---
---   This library provides mechanism to mmap files to fixed address
---   with fine-grained control. Hovewer, instead of using MAP_FIXED we
---   create our own address space upon virtual address space. If you
---   would like you could call this space as "fixed address space".
---
---   This solves a few problems:
---
---     * Page already in use. If you mmap one file at 0..x addresses and
---     want to map second file to x..y addresses using MAP_FIXED you
---     can get in troubles: page might be mapped already. Raw call to
---     mmap will silently unmap x..y addresses and then mmap our second
---     file. So here we have extra unmap we would like to avoid.
---
---     * Page boundaries. If you mmap one file at x..x+1 you could
---     not map next file to say addresses x+1..x+2.
---
---   Internally we make ordinary call to mmap to map a file and then
---   using /interval map/ we map fixed address space to virtual
---   address space. It takes TODO time in TODO cases.
---
---   Basically this library could be used when we need coalesce
---   several files in arbitrary way. We could map at any position as
---   long as offset + size fit in 'Int'.
---
---   For other details see:
---
---   > http://hackage.haskell.org/package/mmap
---   > man mmap
---
-{-# LANGUAGE RecordWildCards #-}
-module System.IO.MMap.Fixed
-       ( -- * Intervals
-         FixedOffset, FileOffset, FixedInterval, FileInterval
-       , interval, fileInterval
-
-         -- * Construction
-       , Fixed, Bytes
-       , System.IO.MMap.Fixed.empty, insertTo
-       , coalesceFiles
-
-         -- ** Specialized 'insertTo'
-       , mmapTo, mallocTo
-       , lookupRegion
-
-         -- * Query
-       , upperAddr
-
-         -- * Access
-       , viewBytes, readBytes, writeBytes
-       , readElem, writeElem
-       ) where
-
-import Data.ByteString.Lazy as Lazy
-import Data.ByteString.Lazy.Internal as Lazy
-import Data.ByteString.Internal as B
-import Data.List as L
-import Data.Int
-import Data.IntervalMap.Strict as M
-import Data.IntervalMap.Interval
-import System.IO.MMap
-import Foreign
-
-
-type FixedOffset = Int
-type FileOffset  = Int64
-type Size   = Int
-
-
-type FileInterval  = (FileOffset, Size)
-type FixedInterval = Interval FixedOffset
-
-
-interval :: FixedOffset -> Size -> FixedInterval
-interval off s = IntervalCO off (off + fromIntegral (max 0 s))
-{-# INLINE interval #-}
-
-fileInterval :: FileOffset -> Size -> FileInterval
-fileInterval off s = (off, s)
-{-# INLINE fileInterval #-}
-
-intervalSize :: FixedInterval -> Size
-intervalSize i = upperBound i - lowerBound i
-{-# INLINE intervalSize #-}
-
-
-type Bytes = (ForeignPtr Word8, Size)
-
-type FixedMap = IntervalMap FixedOffset Bytes
-
-newtype Fixed = Fixed { imap :: FixedMap }
-
-instance Show Fixed where
-  show = show . M.toList . imap
-
-
-mapIM :: (FixedMap -> FixedMap) -> Fixed -> Fixed
-mapIM f s = s { imap = f (imap s) }
-
-empty :: Fixed
-empty = Fixed M.empty
-
-coalesceFiles :: [(FilePath, Int)] -> IO Fixed
-coalesceFiles = go 0 System.IO.MMap.Fixed.empty
-  where
-    go _      s []       = return s
-    go offset s ((path, bsize) : xs) = do
-      s' <- mmapTo path (0, bsize) offset s
-      go (offset + bsize) s' xs
-
-upperAddr :: Fixed -> FixedOffset
-upperAddr = upperBound . fst . findLast . imap
-
-insertTo :: FixedInterval -> Bytes -> Fixed -> Fixed
-insertTo fi mm = mapIM (M.insert fi mm)
-{-# INLINE insertTo #-}
-
-mmapTo :: FilePath -> FileInterval -> FixedOffset -> Fixed -> IO Fixed
-mmapTo path mrange to s = do
-  (fptr, offset, fsize) <- mmapFileForeignPtr path ReadWriteEx (Just mrange)
-
-  let fixed  = interval to fsize
-  let mmaped = (fptr, offset)
-
-  return $ insertTo fixed mmaped s
-
-mallocTo :: FixedInterval -> Fixed -> IO Fixed
-mallocTo fi s = do
-  let bsize = intervalSize fi
-  fptr <- mallocForeignPtrBytes bsize
-  return (insertTo fi (fptr, 0) s)
-
-lookupRegion :: FixedOffset -> Fixed -> Maybe B.ByteString
-lookupRegion offset Fixed {..} =
-  case intersecting imap $ IntervalCO offset (succ offset) of
-    [(i, (fptr, off))] -> let s = upperBound i - lowerBound i
-                          in  Just $ fromForeignPtr fptr off (max 0 s)
-    _         -> Nothing
-
--- | Note: this is unsafe operation.
-viewBytes :: FixedInterval -> Fixed -> Lazy.ByteString
-viewBytes fi s = fromChunks $ L.map mk $ (imap s `intersecting` fi)
-  where
-   mk (i, (fptr, offset)) =
-     let dropB = max 0 (lowerBound fi - lowerBound i)
-         dropT = max 0 (upperBound i  - upperBound fi)
-         bsize = intervalSize i - (dropT + dropB)
-     in fromForeignPtr fptr (offset + dropB) bsize
-
-
-readBytes :: FixedInterval -> Fixed -> IO Lazy.ByteString
-readBytes fi s = let c = Lazy.copy (viewBytes fi s) in mkCopy c >> return c
-{-# INLINE readBytes #-}
-
-writeBytes :: FixedInterval -> Lazy.ByteString -> Fixed -> IO ()
-writeBytes fi bs s = bscpy (viewBytes fi s) bs
-{-# INLINE writeBytes #-}
-
--- | Note: this operation takes O(log(files count)) time, if possible
--- use readBytes.
-readElem :: Storable a => Fixed -> FixedOffset -> IO a
-readElem s offset = go undefined
-  where
-    go :: Storable a => a -> IO a
-    go dont_touch = do
-      let bsize = sizeOf dont_touch
-      let PS fptr off _ = Lazy.toStrict (viewBytes (interval offset bsize) s)
-      withForeignPtr fptr $ \ ptr -> peekByteOff ptr off
-
-writeElem :: Storable a => Fixed -> FixedOffset -> a -> IO ()
-writeElem s offset x = do
-  let bsize = sizeOf x
-  let PS fptr off _ = Lazy.toStrict (viewBytes (interval offset bsize) s)
-  withForeignPtr fptr $ \ptr -> pokeByteOff ptr off x
-
-
-mkCopy :: Lazy.ByteString -> IO ()
-mkCopy Empty = return ()
-mkCopy (Chunk _ x) = mkCopy x
-
-bscpy :: Lazy.ByteString -> Lazy.ByteString -> IO ()
-bscpy (PS _ _ 0 `Chunk` dest_rest) src                         = bscpy dest_rest src
-bscpy dest                         (PS _ _ 0 `Chunk` src_rest) = bscpy dest      src_rest
-bscpy (PS dest_fptr dest_off dest_size `Chunk` dest_rest)
-      (PS src_fptr  src_off  src_size  `Chunk` src_rest)
-  = do let csize = min dest_size src_size
-       withForeignPtr dest_fptr $ \dest_ptr ->
-         withForeignPtr src_fptr $ \src_ptr ->
-           memcpy (dest_ptr `advancePtr` dest_off)
-                  (src_ptr  `advancePtr` src_off)
-                  (fromIntegral csize) -- TODO memmove?
-       bscpy (PS dest_fptr (dest_off + csize) (dest_size - csize) `Chunk` dest_rest)
-             (PS src_fptr  (src_off  + csize) (src_size  - csize) `Chunk` src_rest)
-bscpy _ _ = return ()
\ No newline at end of file
diff --git a/src/System/Torrent/FileMap.hs b/src/System/Torrent/FileMap.hs
new file mode 100644
index 00000000..80907a30
--- /dev/null
+++ b/src/System/Torrent/FileMap.hs
@@ -0,0 +1,151 @@
+{-# LANGUAGE RecordWildCards  #-}
+{-# LANGUAGE ViewPatterns     #-}
+{-# OPTIONS -fno-warn-orphans #-}
+module System.Torrent.FileMap
+       ( FileMap
+
+         -- * Construction
+       , Mode (..)
+       , def
+       , mmapFiles
+       , unmapFiles
+
+         -- * Query
+       , System.Torrent.FileMap.size
+
+         -- * Modification
+       , readBytes
+       , writeBytes
+       , unsafeReadBytes
+
+         -- * Unsafe conversions
+       , fromLazyByteString
+       , toLazyByteString
+       ) where
+
+import Control.Applicative
+import Control.Monad as L
+import Data.ByteString as BS
+import Data.ByteString.Internal as BS
+import Data.ByteString.Lazy as BL
+import Data.ByteString.Lazy.Internal as BL
+import Data.Default
+import Data.Vector as V -- TODO use unboxed vector
+import Foreign
+import System.IO.MMap
+
+import Data.Torrent.Layout
+
+
+data FileEntry = FileEntry
+  { filePosition :: {-# UNPACK #-} !FileOffset
+  , fileBytes    :: {-# UNPACK #-} !BS.ByteString
+  } deriving (Show, Eq)
+
+type FileMap = Vector FileEntry
+
+instance Default Mode where
+  def = ReadWriteEx
+
+mmapFiles :: Mode -> FileLayout FileSize -> IO FileMap
+mmapFiles mode layout = V.fromList <$> L.mapM mkEntry (accumPositions layout)
+  where
+    mkEntry (path, (pos, expectedSize)) = do
+      let esize = fromIntegral expectedSize -- FIXME does this safe?
+      (fptr, moff, msize) <- mmapFileForeignPtr path mode $ Just (0, esize)
+      if msize /= esize
+        then error "mmapFiles" -- TODO unmap mapped files on exception
+        else return $ FileEntry pos (PS fptr moff msize)
+
+unmapFiles :: FileMap -> IO ()
+unmapFiles = V.mapM_ unmapEntry
+  where
+    unmapEntry (FileEntry _ (PS fptr _ _)) = finalizeForeignPtr fptr
+
+fromLazyByteString :: BL.ByteString -> FileMap
+fromLazyByteString lbs = V.unfoldr f (0, lbs)
+  where
+    f (_,   Empty     ) = Nothing
+    f (pos, Chunk x xs) = Just (FileEntry pos x, ((pos + chunkSize), xs))
+      where chunkSize = fromIntegral $ BS.length x
+
+-- | /O(n)/.
+toLazyByteString :: FileMap -> BL.ByteString
+toLazyByteString = V.foldr f Empty
+  where
+    f FileEntry {..} bs = Chunk fileBytes bs
+
+-- | /O(1)/.
+size :: FileMap -> FileOffset
+size m
+  |           V.null m               = 0
+  | FileEntry {..} <- V.unsafeLast m
+  = filePosition + fromIntegral (BS.length fileBytes)
+
+bsearch :: FileOffset -> FileMap -> Maybe Int
+bsearch x m
+  | V.null m  = Nothing
+  | otherwise = branch (V.length m `div` 2)
+  where
+    branch c @ ((m !) -> FileEntry {..})
+      | x <  filePosition            = bsearch x (V.take c m)
+      | x >= filePosition + fileSize = do
+        ix <- bsearch x (V.drop (succ c) m)
+        return $ succ c + ix
+      |          otherwise           = Just c
+      where
+        fileSize = fromIntegral (BS.length fileBytes)
+
+-- | /O(log n)/.
+drop :: FileOffset -> FileMap -> (FileSize, FileMap)
+drop off m
+  | Just ix <- bsearch off m
+  , FileEntry {..} <- m ! ix = (off - filePosition, V.drop ix m)
+  |         otherwise        = (0                 , V.empty)
+
+-- | /O(log n)/.
+take :: FileSize -> FileMap -> (FileMap, FileSize)
+take len m
+  |           len >= s       = (m                 , 0)
+  | Just ix <- bsearch (pred len) m = let m' = V.take (succ ix) m
+                               in (m', System.Torrent.FileMap.size m' - len)
+  |          otherwise       = (V.empty           , 0)
+  where
+    s =  System.Torrent.FileMap.size m
+
+-- | /O(log n + m)/. Do not use this function with 'unmapFiles'.
+unsafeReadBytes :: FileOffset -> FileSize -> FileMap -> BL.ByteString
+unsafeReadBytes off s m
+  | (l  , m') <- System.Torrent.FileMap.drop off     m
+  , (m'', _ ) <- System.Torrent.FileMap.take (off + s) m'
+  = BL.take (fromIntegral s) $ BL.drop (fromIntegral l) $ toLazyByteString m''
+
+readBytes :: FileOffset -> FileSize -> FileMap -> IO BL.ByteString
+readBytes off s m = do
+    let bs_copy = BL.copy $ unsafeReadBytes off s m
+    forceLBS bs_copy
+    return bs_copy
+  where
+    forceLBS  Empty      = return ()
+    forceLBS (Chunk _ x) = forceLBS x
+
+bscpy :: BL.ByteString -> BL.ByteString -> IO ()
+bscpy (PS _ _ 0 `Chunk` dest_rest) src                         = bscpy dest_rest src
+bscpy dest                         (PS _ _ 0 `Chunk` src_rest) = bscpy dest      src_rest
+bscpy (PS dest_fptr dest_off dest_size `Chunk` dest_rest)
+      (PS src_fptr  src_off  src_size  `Chunk` src_rest)
+  = do let csize = min dest_size src_size
+       withForeignPtr dest_fptr $ \dest_ptr ->
+         withForeignPtr src_fptr $ \src_ptr ->
+           memcpy (dest_ptr `advancePtr` dest_off)
+                  (src_ptr  `advancePtr` src_off)
+                  (fromIntegral csize) -- TODO memmove?
+       bscpy (PS dest_fptr (dest_off + csize) (dest_size - csize) `Chunk` dest_rest)
+             (PS src_fptr  (src_off  + csize) (src_size  - csize) `Chunk` src_rest)
+bscpy _ _ = return ()
+
+writeBytes :: FileOffset -> BL.ByteString -> FileMap -> IO ()
+writeBytes off lbs m = bscpy dest src
+  where
+    src  = BL.take (fromIntegral (BL.length dest)) lbs
+    dest = unsafeReadBytes off (fromIntegral (BL.length lbs)) m
\ No newline at end of file
diff --git a/src/System/Torrent/Storage.hs b/src/System/Torrent/Storage.hs
index 2225b0a3..bb6c5d2e 100644
--- a/src/System/Torrent/Storage.hs
+++ b/src/System/Torrent/Storage.hs
@@ -1,11 +1,11 @@
 -- |
---   Copyright   :  (c) Sam T. 2013
---   License     :  MIT
+--   Copyright   :  (c) Sam Truzjan 2013
+--   License     :  BSD3
 --   Maintainer  :  pxqr.sta@gmail.com
 --   Stability   :  experimental
---   Portability :  non-portable
+--   Portability :  portable
 --
---   This module implements mapping from single continious block space
+--   This module implements mapping from single continious piece space
 --   to file storage. Storage can be used in two modes:
 --
 --     * As in memory storage - in this case we don't touch filesystem.
@@ -13,324 +13,55 @@
 --     * As ordinary mmaped file storage - when we need to store
 --       data in the filesystem.
 --
-{-# LANGUAGE DoAndIfThenElse #-}
-{-# LANGUAGE NamedFieldPuns  #-}
-{-# LANGUAGE RecordWildCards #-}
+{-# LANGUAGE RecordWildCards            #-}
 module System.Torrent.Storage
-       ( Storage (metainfo)
-       , ppStorage
+       ( Storage
 
          -- * Construction
-       , openStorage, closeStorage, withStorage
-       , getCompleteBitfield
+       , Mode (..)
+       , def
+       , open
+       , close
 
          -- * Modification
-       , getBlk, putBlk, selBlk
-       , getPiece, validatePiece
-
-         -- * TODO expose only File interface!
-         -- * File interface
-       , FD
-       , openFD, flushFD, closeFD
-       , readFD, writeFD
+       , writePiece
+       , readPiece
+       , unsafeReadPiece
        ) where
 
 import Control.Applicative
-import Control.Concurrent.STM
-import Control.Exception
-import Control.Monad
-import Control.Monad.Trans
-
-import Data.ByteString as B
-import qualified Data.ByteString.Lazy as Lazy
-import Text.PrettyPrint
-import System.FilePath
-import System.Directory
-import Foreign.C.Error
-
-import Data.Torrent.Bitfield as BF
-import Data.Torrent.Block
-import Data.Torrent
-import System.IO.MMap.Fixed as Fixed
-
--- TODO merge piece validation and Sessions.available into one transaction.
-data Storage = Storage {
-    -- |
-    metainfo  :: !Torrent
+import Data.ByteString.Lazy as BL
 
-    -- | Bitmask of complete and verified _pieces_.
-  , complete  :: !(TVar  Bitfield)
+import Data.Torrent.Layout
+import Data.Torrent.Piece
+import System.Torrent.FileMap
 
-    -- | Bitmask of complete _blocks_.
-  , blocks    :: !(TVar Bitfield)
-    -- TODO use bytestring for fast serialization
-    -- because we need to write this bitmap to disc periodically
 
-  , blockSize :: !Int
-
-    -- | Used to map linear block addresses to disjoint
-    -- mallocated/mmaped adresses.
-  , payload :: !Fixed
+-- TODO validation
+data Storage = Storage
+  { pieceLen :: {-# UNPACK #-} !PieceSize
+  , fileMap  :: {-# UNPACK #-} !FileMap
   }
 
-ppStorage :: Storage -> IO Doc
-ppStorage Storage {..} = pp <$> readTVarIO blocks
-  where
-    pp bf = int blockSize
-
-getCompleteBitfield :: Storage -> STM Bitfield
-getCompleteBitfield Storage {..} = readTVar complete
-
-{-----------------------------------------------------------------------
-    Construction
------------------------------------------------------------------------}
+-- ResourceT ?
+open :: Mode -> PieceSize -> FileLayout FileSize -> IO Storage
+open mode s l = Storage s <$> mmapFiles mode l
 
--- TODO doc args
-openStorage :: Torrent -> FilePath -> Bitfield -> IO Storage
-openStorage t @ Torrent {..} contentPath bf = do
-    let content_paths = contentLayout contentPath tInfo
-    mapM_ (mkDir . fst)  content_paths
+close :: Storage -> IO ()
+close Storage {..} = unmapFiles fileMap
 
-    let blockSize = defaultBlockSize `min` ciPieceLength tInfo
-    Storage t <$> newTVarIO bf
-              <*> newTVarIO (haveNone (blockCount blockSize tInfo))
-              <*> pure blockSize
-              <*> coalesceFiles content_paths
-  where
-    mkDir path = do
-      let dirPath = fst (splitFileName path)
-      exist <- doesDirectoryExist dirPath
-      unless exist $ do
-        createDirectoryIfMissing True dirPath
-
--- TODO
-closeStorage :: Storage -> IO ()
-closeStorage st = return ()
-
-
-withStorage :: Torrent -> FilePath -> Bitfield -> (Storage -> IO a) -> IO a
-withStorage se path bf = bracket (openStorage se path bf) closeStorage
+writePiece :: Piece BL.ByteString -> Storage -> IO ()
+writePiece Piece {..} Storage {..} = do
+  writeBytes (fromIntegral (pieceIndex * pieceLen)) pieceData fileMap
 
-{-----------------------------------------------------------------------
-    Modification
------------------------------------------------------------------------}
+readPiece :: PieceIx -> Storage -> IO (Piece BL.ByteString)
+readPiece pix Storage {..} = do
+  bs <- readBytes (fromIntegral (pix * pieceLen))
+                  (fromIntegral pieceLen) fileMap
+  return $ Piece pix bs
 
--- TODO to avoid races we might need to try Control.Concurrent.yield
--- TODO make block_payload :: Lazy.ByteString
-
-selBlk :: MonadIO m => PieceIx -> Storage -> m [BlockIx]
-selBlk pix st @ Storage {..}
-  = liftIO $ {-# SCC selBlk #-} atomically $ do
-    mask <- pieceMask pix st
-    select mask <$> readTVar blocks
+unsafeReadPiece :: PieceIx -> Storage -> IO (Piece BL.ByteString)
+unsafeReadPiece pix Storage {..} = return $ Piece pix lbs
   where
-    select mask = fmap mkBix . toList . difference mask
-    -- TODO clip upper bound of block index
-    mkBix ix  = BlockIx pix (blockSize * (ix - offset)) blockSize
-
-    offset    = coeff * pix
-    coeff     = ciPieceLength (tInfo metainfo)  `div` blockSize
-
---
--- TODO make global lock map -- otherwise we might get broken pieces
---
--- imagine the following situation:
---
---   thread1: write
---   thread1: mark
---
--- this let us avoid races as well
---
-
--- | Write a block to the storage. If block out of range then block is clipped.
---
---
---
-putBlk :: MonadIO m => Block -> Storage -> m Bool
-putBlk blk @ Block {..}  st @ Storage {..}
-  = liftIO $ {-# SCC putBlk #-} do
---  let blkIx = undefined
---  bm <- readTVarIO blocks
---  unless (member blkIx bm) $ do
-    writeBytes (blkInterval (ciPieceLength (tInfo metainfo)) blk)  blkData  payload
-
-    markBlock blk st
-    completePiece blkPiece st
-
-markBlock :: Block -> Storage -> IO ()
-markBlock Block {..} Storage {..} = {-# SCC markBlock #-} do
-  let piLen = ciPieceLength (tInfo metainfo)
-  let glIx  = (piLen `div` blockSize) * blkPiece + (blkOffset `div` blockSize)
-  atomically $ modifyTVar' blocks (have glIx)
-
--- | Read a block by given block index. If lower or upper bound out of
--- range then index is clipped.
---
---  Do not block.
---
-getBlk :: MonadIO m => BlockIx -> Storage -> m Block
-getBlk ix @ BlockIx {..}  st @ Storage {..}
-  = liftIO $ {-# SCC getBlk #-} do
-  -- TODO check if __piece__ is available
-  let piLen = ciPieceLength (tInfo metainfo)
-  bs <- readBytes (ixInterval piLen ix) payload
-  return $ Block ixPiece ixOffset bs
-
-getPiece :: PieceIx -> Storage -> IO Lazy.ByteString
-getPiece pix st @ Storage {..} = {-# SCC getPiece #-} do
-  let piLen = ciPieceLength (tInfo metainfo)
-  let bix   = BlockIx pix 0 piLen
-  let bs    = viewBytes (ixInterval piLen bix) payload
-  return $ bs
-
-resetPiece :: PieceIx -> Storage -> IO ()
-resetPiece pix st @ Storage {..}
-  = {-# SCC resetPiece #-} atomically $ do
-  mask <- pieceMask pix st
-  modifyTVar' blocks (`difference` mask)
-
-validatePiece :: Storage -> PieceIx -> IO Bool
-validatePiece storage pix = do
-  checkPiece (tInfo (metainfo storage)) pix <$> getPiece pix storage
-
-completePiece :: PieceIx -> Storage -> IO Bool
-completePiece pix st @ Storage {..} = {-# SCC completePiece #-} do
-  downloaded <- atomically $ isDownloaded pix st
-  if not downloaded then return False
-    else do
-      piece <- getPiece pix st
-      if checkPiece (tInfo metainfo) pix piece
-        then do
-          atomically $ modifyTVar' complete (BF.have pix)
-          return True
-        else do
-          print $ "----------------------------- invalid " ++ show pix
---          resetPiece pix st
-          return True
-
--- | Check each piece in the storage against content info hash.
---
---   Note that this function will block until each the entire storage
---   checked. This may take a long time for a big torrents ­ use fork
---   if needed.
---
-validateStorage :: Storage -> IO ()
-validateStorage st = undefined -- (`validatePiece` st) [0..pieceCount st]
-
-{-----------------------------------------------------------------------
-  POSIX-like file interface
-------------------------------------------------------------------------
-This is useful for virtual filesystem writers and just for per file
-interface.
------------------------------------------------------------------------}
--- TODO reference counting: storage might be closed before all FDs
--- gets closed!
--- or we can forbid to close storage and use finalizers only?
-
-type Offset = Int
-type Size   = Int
-
-data FD = FD {
-    fdData    :: ByteString
-  , fdNoBlock :: Bool
-  }
-
-
--- TODO return "is dir" error
--- | This call correspond to open(2) with the following parameters:
---
---     * OpenMode = ReadOnly;
---
---     * OpenFileFlags = O_NONBLOCK. (not true yet)
---
-openFD :: FilePath -> Bool -> Storage -> IO (Either Errno FD)
-openFD path nonblock Storage {..}
-  | Just offset <- fileOffset path (tInfo metainfo)
-  , Just bs     <- lookupRegion (fromIntegral offset) payload
-  = return $ Right $ FD bs nonblock
-  | otherwise = return $ Left $ eNOENT
-
--- | Cancel all enqueued read operations and report any delayed
--- errors.
-flushFD :: FD -> IO Errno
-flushFD _ = return eOK
-
--- | This call correspond to close(2).
-closeFD :: FD -> IO ()
-closeFD _ = return ()
-
--- TODO
-maskRegion :: FD -> Offset -> Size -> Maybe Size
-maskRegion FD {..} offset siz = return siz
-
--- TODO
-isComplete :: FD -> Offset -> Size -> IO Size
-isComplete _ _ siz = return siz
-
--- TODO
-enqueueRead :: FD -> Offset -> Size -> IO ()
-enqueueRead _ _ _ = return ()
-
--- TODO
-readAhead :: FD -> Offset -> Size -> IO ()
-readAhead _ _ _ = return ()
-
--- TODO
-waitRegion :: FD -> Offset -> Size -> IO ByteString
-waitRegion _ _ _ = return B.empty
-
--- TODO implement blocking and non blocking modes?
--- TODO check if region completely downloaded
--- TODO if not we could return EAGAIN
--- TODO enqueue read to piece manager
--- | This call correspond to pread(2).
-readFD :: FD -> Offset -> Size -> IO (Either Errno ByteString)
-readFD fd @ FD {..} offset reqSize =
-  case maskRegion fd offset reqSize of
-    Nothing      -> return $ Right B.empty
-    Just expSize -> do
-      availSize <- isComplete fd offset expSize
-      if availSize == expSize then haveAllReg expSize else haveSomeReg expSize
-  where
-    haveAllReg expSize = do
-      readAhead fd offset expSize
-      return $ Right $ slice offset expSize fdData
-
-    haveSomeReg expSize
-      | fdNoBlock = return $ Left $ eAGAIN
-      | otherwise = do
-        bs <- waitRegion fd offset expSize
-        readAhead fd offset expSize
-        return $ Right bs
-
--- TODO implement COW; needed for applications which want to change files.
-writeFD :: FD -> ByteString -> Offset -> IO ()
-writeFD FD {..} bs offset = return ()
-
-{-----------------------------------------------------------------------
-    Internal
------------------------------------------------------------------------}
-
-isDownloaded :: PieceIx -> Storage -> STM Bool
-isDownloaded pix st @ Storage {..} = do
-  bf   <- readTVar blocks
-  mask <- pieceMask pix st
-  return $ intersection mask bf == mask
-
-pieceMask :: PieceIx -> Storage -> STM Bitfield
-pieceMask pix Storage {..} =  do
-    bf <- readTVar blocks
-    return $ BF.interval (totalCount bf) offset (offset + coeff - 1)
-  where
-    offset    = coeff * pix
-    coeff     = ciPieceLength (tInfo metainfo) `div` blockSize
-
-
-ixInterval :: Int -> BlockIx -> FixedInterval
-ixInterval pieceSize BlockIx {..} =
-  Fixed.interval (ixPiece * pieceSize + ixOffset) ixLength
-
-blkInterval :: Int -> Block -> FixedInterval
-blkInterval pieceSize Block {..} =
-  Fixed.interval (blkPiece * pieceSize + blkOffset)
-                 (fromIntegral (Lazy.length blkData))
\ No newline at end of file
+    lbs = unsafeReadBytes (fromIntegral (pix * pieceLen))
+                          (fromIntegral pieceLen) fileMap