Function SlTableHeader

src/saveload/saveload.cpp:1899–2022

* Save or Load a table header. * @note a table-header can never contain more than 65535 fields. * @param slt The SaveLoad table with objects to save/load. * @return When loading, the ordered SaveLoad array to use; otherwise an empty list. */

 * @return When loading, the ordered SaveLoad array to use; otherwise an empty list.
 */
std::vector<SaveLoad> SlTableHeader(const SaveLoadTable &slt)
{
	/* You can only use SlTableHeader if you are a CH_TABLE. */
	assert(_sl.block_mode == CH_TABLE || _sl.block_mode == CH_SPARSE_TABLE);

	switch (_sl.action) {
		case SLA_LOAD_CHECK:
		case SLA_LOAD: {
			std::vector<SaveLoad> saveloads;

			/* Build a key lookup mapping based on the available fields. */
			std::map<std::string, const SaveLoad *> key_lookup;
			for (auto &sld : slt) {
				if (!SlIsObjectValidInSavegame(sld)) continue;

				/* Check that there is only one active SaveLoad for a given name. */
				assert(key_lookup.find(sld.name) == key_lookup.end());
				key_lookup[sld.name] = &sld;
			}

			while (true) {
				uint8_t type = 0;
				SlSaveLoadConv(&type, SLE_UINT8);
				if (type == SLE_FILE_END) break;

				std::string key;
				SlStdString(&key, SLE_STR);

				auto sld_it = key_lookup.find(key);
				if (sld_it == key_lookup.end()) {
					/* SLA_LOADCHECK triggers this debug statement a lot and is perfectly normal. */
					Debug(sl, _sl.action == SLA_LOAD ? 2 : 6, "Field '{}' of type 0x{:02x} not found, skipping", key, type);

					std::shared_ptr<SaveLoadHandler> handler = nullptr;
					SaveLoadType saveload_type;
					switch (type & SLE_FILE_TYPE_MASK) {
						case SLE_FILE_STRING:
							/* Strings are always marked with SLE_FILE_HAS_LENGTH_FIELD, as they are a list of chars. */
							saveload_type = SL_STDSTR;
							break;

						case SLE_FILE_STRUCT:
							/* Structs are always marked with SLE_FILE_HAS_LENGTH_FIELD as SL_STRUCT is seen as a list of 0/1 in length. */
							saveload_type = SL_STRUCTLIST;
							handler = std::make_shared<SlSkipHandler>();
							break;

						default:
							saveload_type = (type & SLE_FILE_HAS_LENGTH_FIELD) ? SL_ARR : SL_VAR;
							break;
					}

					/* We don't know this field, so read to nothing. */
					saveloads.emplace_back(std::move(key), saveload_type, ((VarType)type & SLE_FILE_TYPE_MASK) | SLE_VAR_NULL, 1, SL_MIN_VERSION, SL_MAX_VERSION, nullptr, 0, std::move(handler));
					continue;
				}

				/* Validate the type of the field. If it is changed, the