code: func (t *Torrent) reapPieceTouchers(piece pieceIndex) (ret []*connection) {
  	for c := range t.pieces[piece].dirtiers {
  		delete(c.peerTouchedPieces, piece)
  		ret = append(ret, c)
  	}
  	t.pieces[piece].dirtiers = nil
  	return
  }
docs: // Return the connections that touched a piece, and clear the entries while
  // doing it.