fixed bug in storage when forcing recheck while renaming a file or moving it

docs/manual.rst

@@ -5112,12 +5112,30 @@ storage_interface
 =================
 
 The storage interface is a pure virtual class that can be implemented to
-change the behavior of the actual file storage. The interface looks like
-this::
+customize how and where data for a torrent is stored. The default storage
+implementation uses regular files in the filesystem, mapping the files in the
+torrent in the way one would assume a torrent is saved to disk. Implementing
+your own storage interface makes it possible to store all data in RAM, or in
+some optimized order on disk (the order the pieces are received for instance),
+or saving multifile torrents in a single file in order to be able to take
+advantage of optimized disk-I/O.
+
+It is also possible to write a thin class that uses the default storage but
+modifies some particular behavior, for instance encrypting the data before
+it's written to disk, and decrypting it when it's read again.
+
+The storage interface is based on slots, each slot is 'piece_size' number
+of bytes. All access is done by writing and reading whole or partial
+slots. One slot is one piece in the torrent, but the data in the slot
+does not necessarily correspond to the piece with the same index (in
+compact allocation mode it won't).
+
+The interface looks like this::
 
 	struct storage_interface
 	{
 		virtual bool initialize(bool allocate_files) = 0;
+		virtual bool has_any_file() = 0;
 		virtual int readv(file::iovec_t const* bufs, int slot, int offset, int num_bufs) = 0;
 		virtual int writev(file::iovec_t const* bufs, int slot, int offset, int num_bufs) = 0;
 		virtual int sparse_end(int start) const;
@@ -5156,6 +5174,16 @@ it will also ``ftruncate`` all files to their target size.
 
 Returning ``true`` indicates an error occurred.
 
+has_any_file()
+--------------
+
+	::
+
+		virtual bool has_any_file() = 0;
+
+This function is called when first checking (or re-checking) the storage for a torrent.
+It should return true if any of the files that is used in this storage exists on disk.
+If so, the storage will be checked for existing pieces before starting the download.
 
 readv() writev()
 ----------------

include/libtorrent/storage.hpp

@@ -119,6 +119,8 @@ namespace libtorrent
 		// false return value indicates an error
 		virtual bool initialize(bool allocate_files) = 0;
 
+		virtual bool has_any_file() = 0;
+
 		virtual int readv(file::iovec_t const* bufs, int slot, int offset, int num_bufs);
 		virtual int writev(file::iovec_t const* bufs, int slot, int offset, int num_bufs);
 

src/storage.cpp

@@ -407,6 +407,7 @@ namespace libtorrent
 #endif
 		}
 
+		bool has_any_file();
 		bool rename_file(int index, std::string const& new_filename);
 		bool release_files();
 		bool delete_files();
@@ -581,6 +582,43 @@ namespace libtorrent
 		return false;
 	}
 
+	bool storage::has_any_file()
+	{
+		file_storage::iterator i = files().begin();
+		file_storage::iterator end = files().end();
+
+		for (; i != end; ++i)
+		{
+			bool file_exists = false;
+			fs::path f = m_save_path / i->path;
+#ifndef BOOST_NO_EXCEPTIONS
+			try
+			{
+#endif
+#if TORRENT_USE_WPATH
+				fs::wpath wf = convert_to_wstring(f.string());
+				file_exists = exists(wf);
+#elif TORRENT_USE_LOCALE_FILENAMES
+				file_exists = exists(convert_to_native(f.string()));
+#else
+				file_exists = exists(f);
+#endif
+				std::cerr << "has_any_file(): " << f << " " << (file_exists?"exists": "don't exist")
+					<< std::endl;
+#ifndef BOOST_NO_EXCEPTIONS
+			}
+			catch (boost::system::system_error& e)
+			{
+				set_error(f, e.code());
+				return false;
+			}
+#endif
+			if (file_exists && i->size > 0)
+				return true;
+		}
+		return false;
+	}
+
 	bool storage::rename_file(int index, std::string const& new_filename)
 	{
 		if (index < 0 || index >= m_files.num_files()) return true;
@@ -1857,53 +1895,27 @@ ret:
 
 	int piece_manager::check_no_fastresume(std::string& error)
 	{
-		file_storage::iterator i = m_files.begin();
-		file_storage::iterator end = m_files.end();
+		bool has_files = m_storage->has_any_file();
 
-		for (; i != end; ++i)
+		if (m_storage->error())
+			return fatal_disk_error;
+
+		if (has_files)
 		{
-			bool file_exists = false;
-			fs::path f = m_save_path / i->path;
-#ifndef BOOST_NO_EXCEPTIONS
-			try
+			m_state = state_full_check;
+			m_piece_to_slot.clear();
+			m_piece_to_slot.resize(m_files.num_pieces(), has_no_slot);
+			m_slot_to_piece.clear();
+			m_slot_to_piece.resize(m_files.num_pieces(), unallocated);
+			if (m_storage_mode == storage_mode_compact)
 			{
-#endif
-#if TORRENT_USE_WPATH
-				fs::wpath wf = convert_to_wstring(f.string());
-				file_exists = exists(wf);
-#elif TORRENT_USE_LOCALE_FILENAMES
-				file_exists = exists(convert_to_native(f.string()));
-#else
-				file_exists = exists(f);
-#endif
-#ifndef BOOST_NO_EXCEPTIONS
-			}
-			catch (std::exception& e)
-			{
-				error = f.string();
-				error += ": ";
-				error += e.what();
-				TORRENT_ASSERT(!error.empty());
-				return fatal_disk_error;
-			}
-#endif
-			if (file_exists && i->size > 0)
-			{
-				m_state = state_full_check;
-				m_piece_to_slot.clear();
-				m_piece_to_slot.resize(m_files.num_pieces(), has_no_slot);
-				m_slot_to_piece.clear();
-				m_slot_to_piece.resize(m_files.num_pieces(), unallocated);
-				if (m_storage_mode == storage_mode_compact)
-				{
-					m_unallocated_slots.clear();
-					m_free_slots.clear();
-				}
-				TORRENT_ASSERT(int(m_piece_to_slot.size()) == m_files.num_pieces());
-				return need_full_check;
+				m_unallocated_slots.clear();
+				m_free_slots.clear();
 			}
+			TORRENT_ASSERT(int(m_piece_to_slot.size()) == m_files.num_pieces());
+			return need_full_check;
 		}
-	
+
 		if (m_storage_mode == storage_mode_compact)
 		{
 			// in compact mode without checking, we need to

src/torrent.cpp

@@ -804,10 +804,6 @@ namespace libtorrent
 		disconnect_all();
 
 		m_owning_storage->async_release_files();
-		m_owning_storage = new piece_manager(shared_from_this(), m_torrent_file
-			, m_save_path, m_ses.m_files, m_ses.m_disk_thread, m_storage_constructor
-			, m_storage_mode);
-		m_storage = m_owning_storage.get();
 		if (!m_picker) m_picker.reset(new piece_picker());
 		m_picker->init(m_torrent_file->piece_length() / m_block_size
 			, int((m_torrent_file->total_size()+m_block_size-1)/m_block_size));
@@ -845,9 +841,17 @@ namespace libtorrent
 			pause();
 			return;
 		}
-		set_state(torrent_status::queued_for_checking);
-		if (should_check_files())
-			queue_torrent_check();
+		if (ret == 0)
+		{
+			// if there are no files, just start
+			files_checked();
+		}
+		else
+		{
+			set_state(torrent_status::queued_for_checking);
+			if (should_check_files())
+				queue_torrent_check();
+		}
 	}
 
 	void torrent::start_checking()