Function DoLoad

src/saveload/saveload.cpp:3138–3231

* Actually perform the loading of a "non-old" savegame. * @param reader The filter to read the savegame from. * @param load_check Whether to perform the checking ("preview") or actually load the game. * @return Return the result of the action. #SL_OK or #SL_REINIT ("unload" the game) */

 * @return Return the result of the action. #SL_OK or #SL_REINIT ("unload" the game)
 */
static SaveOrLoadResult DoLoad(std::shared_ptr<LoadFilter> reader, bool load_check)
{
	_sl.lf = std::move(reader);

	if (load_check) {
		/* Clear previous check data */
		_load_check_data.Clear();
		/* Mark SL_LOAD_CHECK as supported for this savegame. */
		_load_check_data.checkable = true;
	}

	uint32_t hdr[2];
	if (_sl.lf->Read((uint8_t*)hdr, sizeof(hdr)) != sizeof(hdr)) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_READABLE);

	/* see if we have any loader for this type. */
	const SaveLoadFormat *fmt = DetermineSaveLoadFormat(hdr[0], hdr[1]);

	/* loader for this savegame type is not implemented? */
	if (fmt->init_load == nullptr) {
		SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_INTERNAL_ERROR, fmt::format("Loader for '{}' is not available.", fmt->name));
	}

	_sl.lf = fmt->init_load(_sl.lf);
	_sl.reader = std::make_unique<ReadBuffer>(_sl.lf);
	_next_offs = 0;

	if (!load_check) {
		ResetSaveloadData();

		/* Old maps were hardcoded to 256x256 and thus did not contain
		 * any mapsize information. Pre-initialize to 256x256 to not to
		 * confuse old games */
		InitializeGame(256, 256, true, true);

		_gamelog.Reset();

		if (IsSavegameVersionBefore(SLV_4)) {
			/*
			 * NewGRFs were introduced between 0.3,4 and 0.3.5, which both
			 * shared savegame version 4. Anything before that 'obviously'
			 * does not have any NewGRFs. Between the introduction and
			 * savegame version 41 (just before 0.5) the NewGRF settings
			 * were not stored in the savegame and they were loaded by
			 * using the settings from the main menu.
			 * So, to recap:
			 * - savegame version  <  4:  do not load any NewGRFs.
			 * - savegame version >= 41:  load NewGRFs from savegame, which is
			 *                            already done at this stage by
			 *                            overwriting the main menu settings.
			 * - other savegame versions: use main menu settings.
			 *
			 * This means that users *can* crash savegame version 4..40
			 * savegames if they set incompatible NewGRFs in the main menu,
			 * but can't crash anymore for savegame version < 4 savegames.
			 *
			 * Note: this is done here because AfterLoadGame is also called
			 * for TTO/TTD/TTDP savegames which have their own NewGRF logic.
			 */