first version of 'part file' support. Can currently only be set when starting torrent

docs/manual.rst

@@ -918,7 +918,7 @@ The ``torrent_info`` has the following synopsis::
 		typedef std::vector<file_entry>::const_reverse_iterator
 			reverse_file_iterator;
 
-		bool remap_files(std::vector<std::pair<std::string, libtorrent::size_type> > const& map);
+		bool remap_files(std::vector<file_entry> const& map);
 
 		file_iterator begin_files(bool storage = false) const;
 		file_iterator end_files(bool storage = false) const;
@@ -1052,18 +1052,20 @@ remap_files()
 
 	::
 
-		bool remap_files(std::vector<std::pair<std::string, libtorrent::size_type> > const& map);
+		bool remap_files(std::vector<file_entry> const& map);
 
 This call will create a new mapping of the data in this torrent to other files. The
 ``torrent_info`` maintains 2 views of the file storage. One that is true to the torrent
 file, and one that represents what is actually saved on disk. This call will change
 what the files on disk are called.
 
-The each entry in the vector ``map`` is a pair of a (relative) file path and the file's size.
+The each entry in the vector ``map`` is a ``file_entry``. The only fields in this struct
+that are used in this case are ``path``, ``size`` and ``file_base``.
 
 The return value indicates if the remap was successful or not. True means success and
 false means failure. The sum of all the files passed in through ``map`` has to be exactly
-the same as the total_size of the torrent.
+the same as the total_size of the torrent. If the number of bytes that are mapped do not
+match, false will be returned (this is the only case this function may fail).
 
 Changing this mapping for an existing torrent will not move or rename files. If some files
 should be renamed, this can be done before the torrent is added.
@@ -1097,6 +1099,7 @@ remapped, they may differ. For more info, see `remap_files()`_.
 		boost::filesystem::path path;
 		size_type offset;
 		size_type size;
+		size_type file_base;
 		boost::shared_ptr<const boost::filesystem::path> orig_path;
 	};
 
@@ -1108,6 +1111,13 @@ The filenames are encoded with UTF-8.
 of the file within the torrent. i.e. the sum of all the sizes of the files
 before it in the list.
 
+``file_base`` is the offset in the file where the storage should start. The normal
+case is to have this set to 0, so that the storage starts saving data at the start
+if the file. In cases where multiple files are mapped into the same file though,
+the ``file_base`` should be set to an offset so that the different regions do
+not overlap. This is used when mapping "unselected" files into a so-called part
+file.
+
 ``orig_path`` is set to 0 in case the path element is an exact copy of that
 found in the metadata. In case the path in the original metadata was
 incorrectly encoded, and had to be fixed in order to be acceptable utf-8,

include/libtorrent/torrent_info.hpp

@@ -69,9 +69,15 @@ namespace libtorrent
 
 	struct TORRENT_EXPORT file_entry
 	{
+		file_entry(): offset(0), size(0), file_base(0) {}
+
 		fs::path path;
 		size_type offset; // the offset of this file inside the torrent
 		size_type size; // the size of this file
+		// the offset in the file where the storage starts.
+		// This is always 0 unless parts of the torrent is
+		// compressed into a single file, such as a so-called part file.
+		size_type file_base;
 		// if the path was incorrectly encoded, this is
 		// the original corrupt encoded string. It is
 		// preserved in order to be able to reproduce
@@ -117,7 +123,7 @@ namespace libtorrent
 		void add_file(fs::path file, size_type size);
 		void add_url_seed(std::string const& url);
 
-		bool remap_files(std::vector<std::pair<std::string, libtorrent::size_type> > const& map);
+		bool remap_files(std::vector<file_entry> const& map);
 
 		std::vector<file_slice> map_block(int piece, size_type offset
 			, int size, bool storage = false) const;
@@ -271,7 +277,7 @@ namespace libtorrent
 
 		// this vector is typically empty. If it is not
 		// empty, it means the user has re-mapped the
-		// files in this torrent to diffefrent names
+		// files in this torrent to different names
 		// on disk. This is only used when reading and
 		// writing the disk.
 		std::vector<file_entry> m_remapped_files;

src/storage.cpp

@@ -768,10 +768,10 @@ namespace libtorrent
 
 		TORRENT_ASSERT(file_offset < file_iter->size);
 
-		TORRENT_ASSERT(slices[0].offset == file_offset);
+		TORRENT_ASSERT(slices[0].offset == file_offset + file_iter->file_base);
 
-		size_type new_pos = in->seek(file_offset);
+		size_type new_pos = in->seek(file_offset + file_iter->file_base);
-		if (new_pos != file_offset)
+		if (new_pos != file_offset + file_iter->file_base)
 		{
 			// the file was not big enough
 			if (!fill_zero)
@@ -782,7 +782,7 @@ namespace libtorrent
 
 #ifndef NDEBUG
 		size_type in_tell = in->tell();
-		TORRENT_ASSERT(in_tell == file_offset);
+		TORRENT_ASSERT(in_tell == file_offset + file_iter->file_base);
 #endif
 
 		int left_to_read = size;
@@ -846,7 +846,7 @@ namespace libtorrent
 				file_offset = 0;
 				in = m_files.open_file(
 					this, path, file::in);
-				in->seek(0);
+				in->seek(file_iter->file_base);
 			}
 		}
 		return result;
@@ -892,11 +892,11 @@ namespace libtorrent
 			this, p, file::out | file::in);
 
 		TORRENT_ASSERT(file_offset < file_iter->size);
-		TORRENT_ASSERT(slices[0].offset == file_offset);
+		TORRENT_ASSERT(slices[0].offset == file_offset + file_iter->file_base);
 
-		size_type pos = out->seek(file_offset);
+		size_type pos = out->seek(file_offset + file_iter->file_base);
 
-		if (pos != file_offset)
+		if (pos != file_offset + file_iter->file_base)
 		{
 			std::stringstream s;
 			s << "no storage for slot " << slot;
@@ -962,7 +962,7 @@ namespace libtorrent
 				out = m_files.open_file(
 					this, p, file::out | file::in);
 
-				out->seek(0);
+				out->seek(file_iter->file_base);
 			}
 		}
 	}

src/torrent_info.cpp

@@ -165,7 +165,7 @@ namespace
 	{
 		target.size = dict["length"].integer();
 		target.path = root_dir;
-
+		target.file_base = 0;
 
 		// prefer the name.utf-8
 		// because if it exists, it is more
@@ -824,20 +824,19 @@ namespace libtorrent
 		m_nodes.push_back(node);
 	}
 
-	bool torrent_info::remap_files(std::vector<std::pair<std::string
+	bool torrent_info::remap_files(std::vector<file_entry> const& map)
-		, libtorrent::size_type> > const& map)
 	{
-		typedef std::vector<std::pair<std::string, size_type> > files_t;
-
 		size_type offset = 0;
 		m_remapped_files.resize(map.size());
 
 		for (int i = 0; i < int(map.size()); ++i)
 		{
 			file_entry& fe = m_remapped_files[i];
-			fe.path = map[i].first;
+			fe.path = map[i].path;
 			fe.offset = offset;
-			fe.size = map[i].second;
+			fe.size = map[i].size;
+			fe.file_base = map[i].file_base;
+			fe.orig_path.reset();
 			offset += fe.size;
 		}
 		if (offset != total_size())
@@ -846,6 +845,26 @@ namespace libtorrent
 			return false;
 		}
 
+#ifndef NDEBUG
+		std::vector<file_entry> map2(m_remapped_files);
+		std::sort(map2.begin(), map2.end()
+			, bind(&file_entry::file_base, _1) < bind(&file_entry::file_base, _2));
+		std::stable_sort(map2.begin(), map2.end()
+			, bind(&file_entry::path, _1) < bind(&file_entry::path, _2));
+		fs::path last_path;
+		size_type last_end = 0;
+		for (std::vector<file_entry>::iterator i = map2.begin(), end(map2.end());
+			i != end; ++i)
+		{
+			if (last_path == i->path)
+			{
+				assert(last_end <= i->file_base);
+			}
+			last_end = i->file_base + i->size;
+			last_path = i->path;
+		}
+#endif
+
 		return true;
 	}
 
@@ -871,7 +890,7 @@ namespace libtorrent
 			{
 				file_slice f;
 				f.file_index = counter;
-				f.offset = file_offset;
+				f.offset = file_offset + file_iter->file_base;
 				f.size = (std::min)(file_iter->size - file_offset, (size_type)size);
 				size -= f.size;
 				file_offset += f.size;

test/test_storage.cpp

@@ -192,8 +192,17 @@ void run_test(path const& test_path)
 // ==============================================
 
 	// make sure remap_files works
-	std::vector<std::pair<std::string, libtorrent::size_type> > map;
+	std::vector<file_entry> map;
-	map.push_back(std::make_pair(std::string("temp_storage/test.tmp"), 17 + 612 + 1));
+	file_entry fe;
+	fe.path = "temp_storage/test.tmp";
+	fe.size = 17;
+	fe.file_base = 612 + 1;
+	map.push_back(fe);
+	fe.path = "temp_storage/test.tmp";
+	fe.size = 612 + 1;
+	fe.file_base = 0;
+	map.push_back(fe);
+
 	bool ret = info->remap_files(map);
 	TEST_CHECK(ret);
 
@@ -202,7 +211,7 @@ void run_test(path const& test_path)
 	run_storage_tests(info, test_path, storage_mode_compact);
 
 	std::cerr << file_size(test_path / "temp_storage" / "test.tmp") << std::endl;
-	TEST_CHECK(file_size(test_path / "temp_storage" / "test.tmp") == 48);
+	TEST_CHECK(file_size(test_path / "temp_storage" / "test.tmp") == 17 + 612 + 1);
 
 	remove_all(test_path / "temp_storage");