C++ Train::First方法代码示例

/**
 * Autoreplaces a vehicle
 * Trains are replaced as a whole chain, free wagons in depot are replaced on their own
 * @param tile not used
 * @param flags type of operation
 * @param p1 Index of vehicle
 * @param p2 not used
 * @param text unused
 * @return the cost of this operation or an error
 */
CommandCost CmdAutoreplaceVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text)
{
	Vehicle *v = Vehicle::GetIfValid(p1);
	if (v == NULL) return CMD_ERROR;

	CommandCost ret = CheckOwnership(v->owner);
	if (ret.Failed()) return ret;

	if (!v->IsInDepot()) return CMD_ERROR;
	if (v->vehstatus & VS_CRASHED) return CMD_ERROR;

	bool free_wagon = false;
	if (v->type == VEH_TRAIN) {
		Train *t = Train::From(v);
		if (t->IsArticulatedPart() || t->IsRearDualheaded()) return CMD_ERROR;
		free_wagon = !t->IsFrontEngine();
		if (free_wagon && t->First()->IsFrontEngine()) return CMD_ERROR;
	} else {
		if (!v->IsPrimaryVehicle()) return CMD_ERROR;
	}

	const Company *c = Company::Get(_current_company);
	bool wagon_removal = c->settings.renew_keep_length;

	/* Test whether any replacement is set, before issuing a whole lot of commands that would end in nothing changed */
	Vehicle *w = v;
	bool any_replacements = false;
	while (w != NULL) {
		EngineID e;
		CommandCost cost = GetNewEngineType(w, c, e);
		if (cost.Failed()) return cost;
		any_replacements |= (e != INVALID_ENGINE);
		w = (!free_wagon && w->type == VEH_TRAIN ? Train::From(w)->GetNextUnit() : NULL);
	}

	CommandCost cost = CommandCost(EXPENSES_NEW_VEHICLES, 0);
	bool nothing_to_do = true;

	if (any_replacements) {
		bool was_stopped = free_wagon || ((v->vehstatus & VS_STOPPED) != 0);

		/* Stop the vehicle */
		if (!was_stopped) cost.AddCost(CmdStartStopVehicle(v, true));
		if (cost.Failed()) return cost;

		assert(v->IsStoppedInDepot());

		/* We have to construct the new vehicle chain to test whether it is valid.
		 * Vehicle construction needs random bits, so we have to save the random seeds
		 * to prevent desyncs and to replay newgrf callbacks during DC_EXEC */
		SavedRandomSeeds saved_seeds;
		SaveRandomSeeds(&saved_seeds);
		if (free_wagon) {
			cost.AddCost(ReplaceFreeUnit(&v, flags & ~DC_EXEC, &nothing_to_do));
		} else {
			cost.AddCost(ReplaceChain(&v, flags & ~DC_EXEC, wagon_removal, &nothing_to_do));
		}
		RestoreRandomSeeds(saved_seeds);

		if (cost.Succeeded() && (flags & DC_EXEC) != 0) {
			CommandCost ret;
			if (free_wagon) {
				ret = ReplaceFreeUnit(&v, flags, &nothing_to_do);
			} else {
				ret = ReplaceChain(&v, flags, wagon_removal, &nothing_to_do);
			}
			assert(ret.Succeeded() && ret.GetCost() == cost.GetCost());
		}

		/* Restart the vehicle */
		if (!was_stopped) cost.AddCost(CmdStartStopVehicle(v, false));
	}

	if (cost.Succeeded() && nothing_to_do) cost = CommandCost(STR_ERROR_AUTOREPLACE_NOTHING_TO_DO);
	return cost;
}