LevelDB as default & automatic migration (#30)

* Automatic migration to LevelDB backend (only on Android by default)

* Use LevelDB as default backend

src/game.cpp

@@ -58,7 +58,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "version.h"
 #include "minimap.h"
 #include "mapblock_mesh.h"
-
+#include "database.h"
 #include "sound.h"
 
 #if USE_SOUND
@@ -1500,6 +1500,7 @@ protected:
 	bool initSound();
 	bool createSingleplayerServer(const std::string map_dir,
 			const SubgameSpec &gamespec, u16 port, std::string *address);
+	bool autoMigrateSingleplayerWorld(const std::string map_dir);
 
 	// Client creation
 	bool createClient(const std::string &playername,
@@ -2044,6 +2045,8 @@ bool Game::createSingleplayerServer(const std::string map_dir,
 		return false;
 	}
 
+	autoMigrateSingleplayerWorld(map_dir);
+
 	server = new Server(map_dir, gamespec, simple_singleplayer_mode,
 			    bind_addr.isIPv6());
 
@@ -2052,6 +2055,62 @@ bool Game::createSingleplayerServer(const std::string map_dir,
 	return true;
 }
 
+bool Game::autoMigrateSingleplayerWorld(const std::string map_dir)
+{
+	const std::string new_backend = "leveldb";
+
+#ifndef __ANDROID__
+	infostream << "Auto-migration disabled on this platform..." << std::endl;
+	return false;
+#endif
+
+	// Check if needed for this world
+	Settings world_mt;
+	std::string world_mt_path = map_dir + DIR_DELIM + "world.mt";
+	if (!world_mt.readConfigFile(world_mt_path.c_str())) {
+		infostream << "Skipping migration check as world.mt can't be read." << std::endl;
+		return false;
+	}
+	if (!world_mt.exists("backend"))
+		return false;
+	std::string old_backend = world_mt.get("backend");
+	if (old_backend == new_backend) {
+		infostream << "Backend matches, not migrating world!" << std::endl;
+		return false;
+	}
+
+	// Do migration
+	showOverlayMessage(wgettext("Migrating world..."), 0, 7.5);
+	infostream << "Doing auto-migration to " << new_backend << " backend." << std::endl;
+	Database *old_db = ServerMap::createDatabase(old_backend, map_dir, world_mt),
+		*new_db = ServerMap::createDatabase(new_backend, map_dir, world_mt);
+
+	std::vector<v3s16> blocks;
+	old_db->listAllLoadableBlocks(blocks);
+	new_db->beginSave();
+	for (std::vector<v3s16>::const_iterator it = blocks.begin(); it != blocks.end(); ++it) {
+		std::string data;
+		old_db->loadBlock(*it, &data);
+		if (!data.empty())
+			new_db->saveBlock(*it, data);
+		else
+			errorstream << "Failed to load block " << PP(*it) << ", skipping it." << std::endl;
+	}
+	new_db->endSave();
+	delete old_db;
+	delete new_db;
+
+	world_mt.set("backend", new_backend);
+	world_mt.updateConfigFile(world_mt_path.c_str());
+
+	// Delete old map data if possible
+	if (old_backend == "sqlite3")
+		fs::DeleteSingleFileOrEmptyDirectory(map_dir + DIR_DELIM + "map.sqlite");
+
+	infostream << "Migration successful!" << std::endl;
+	return true;
+}
+
 bool Game::createClient(const std::string &playername,
 		const std::string &password, std::string *address, u16 port)
 {

src/subgame.cpp

@@ -293,7 +293,7 @@ bool loadGameConfAndInitWorld(const std::string &path, const SubgameSpec &gamesp
 	if (!fs::PathExists(worldmt_path)) {
 		std::ostringstream ss(std::ios_base::binary);
 		ss << "gameid = " << gamespec.id
-			<< "\nbackend = sqlite3"
+			<< "\nbackend = leveldb"
 			<< "\ncreative_mode = " << g_settings->get("creative_mode")
 			<< "\nenable_damage = " << g_settings->get("enable_damage")
 			<< "\n";