add not_corrupt() function in saved_game class

and add comments about other functions.

src/saved_game.cpp

@@ -167,6 +167,7 @@ void saved_game::write_starting_pos(config_writer& out) const
 }
 void saved_game::write_carryover(config_writer& out) const
 {
+	assert(not_corrupt());
 	if(!this->carryover_sides.empty())
 	{
 		out.write_child("carryover_sides", carryover_sides);	
@@ -342,3 +343,19 @@ std::string saved_game::get_scenario_id()
 		return carryover_sides_start["next_scenario"];
 	}
 }
+
+
+bool saved_game::not_corrupt() const
+{
+	if(carryover_sides.empty() && carryover_sides_start.empty())
+	{
+		//this case is dangerous but currently not impossible.
+		WRN_NG << "savefile contains neigher [carryover_sides] not [carryover_sides_start]" <<  std::endl;
+	}
+	// A Scenario can never contain both of them
+	// normal saves have [carryover_sides] start-of-scenario saved have [carryover_sides_start]
+	// the function expand_carryover transforms a start of scenario save to a normal save
+	// the function convert_to_start_save converts a normal save form teh end of the scenaio 
+	// to a start-of-scenario save for a next level
+	return carryover_sides.empty() || carryover_sides_start.empty();
+}

src/saved_game.hpp

@@ -30,6 +30,7 @@ class saved_game
 	void write_carryover(config_writer& out) const;
 	void write_starting_pos(config_writer& out) const;
 	config to_config();
+	///Removes everything except [carryover_sides_start]
 	void remove_old_scenario();
 	game_classification& classification() { return classification_; }
 	const game_classification& classification() const { return classification_; }
@@ -51,13 +52,19 @@ class saved_game
 	{
 		return starting_pos_type_ == STARTINGPOS_SNAPSHOT;
 	}
+	/// converts a normal savegame form the end of a scenaio to a start-of-scenario savefiel for teh next scenaio, 
+	/// The saved_game must contain a [snapshot] made during the linger mode of the last scenaio.
 	void convert_to_start_save();
+	/// retruns from the config from which the replay will be started. Usualy this is [replay_start] but it can also be a [scenario] if no replay_start is present
 	const config& get_replay_starting_pos();
-
+	/// returns the id of teh curently played scenaio or the id of the next scenaio if this is a between-scenaios-save (also called start-of-scenario) save.
 	std::string get_scenario_id();
+	/// retruns from the config from which teh game will be started. [scenario] or [snapshot] in the file
 	config& get_starting_pos();
 	config& replay_start() { return replay_start_; }
 	const config& replay_start() const { return replay_start_; }
+
+	bool not_corrupt() const;
 	/**
 	 * If the game is saved mid-level, we have a series of replay steps
 	 * to take the game up to the position it was saved at.