1 files changed, 10 insertions, 0 deletions

diff --git a/src/Network/BitTorrent/Exchange/Block.hs b/src/Network/BitTorrent/Exchange/Block.hs
index c910a716..32e4f99f 100644
--- a/src/Network/BitTorrent/Exchange/Block.hs
+++ b/src/Network/BitTorrent/Exchange/Block.hs
@@ -30,6 +30,7 @@ module Network.BitTorrent.Exchange.Block
        , blockSize
        , blockRange
        , isPiece
+       , leadingBlock
 
          -- * Block bucket
        , Bucket
@@ -194,6 +195,15 @@ isPiece pieceLen blk @ (Block i offset _) =
      offset == 0 && blockSize blk == pieceLen && i >= 0
 {-# INLINE isPiece #-}
 
+-- | First block in the piece.
+leadingBlock :: PieceIx -> BlockSize -> BlockIx
+leadingBlock pix blockSize = BlockIx
+  { ixPiece  = pix
+  , ixOffset = 0
+  , ixLength = blockSize
+  }
+{-# INLINE leadingBlock #-}
+
 {-----------------------------------------------------------------------
 --  Bucket
 -----------------------------------------------------------------------}