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Eric Sysoev
Eric Sysoev

SteamAPI Unregistercallresult: A simple and effective way to handle async function calls - CodeProject



What is steamAPI Unregistercallresult and why you should know about it




If you are a game developer or a modder who uses Steamworks SDK to integrate your game with Steam features, you might have encountered the function steamAPI Unregistercallresult in your code. But what does this function do, and why is it important to use it correctly? In this article, we will explain what steamAPI Unregistercallresult is, how it works, how to use it in your code, and what are the best practices and tips for using it effectively. By the end of this article, you will have a better understanding of this function and how it can help you improve your game's performance, stability, and user experience.




steamAPI Unregistercallresult



How steamAPI works and what are call results




The basics of steamAPI and its functions




Steamworks SDK is a set of tools and APIs that allow you to integrate your game with Steam features, such as achievements, leaderboards, multiplayer, cloud storage, workshop, etc. To use Steamworks SDK, you need to include the header file steam_api.h in your code, which provides access to various interfaces and functions that interact with Steam client and games.


One of the most important interfaces in Steamworks SDK is ISteamClient, which is the main entry point for accessing all other interfaces. You can get an instance of ISteamClient by calling SteamClient(), which is a global accessor function defined in steam_api.h. You can then use ISteamClient to create various user or game server instances that represent different Steam accounts or game servers. For example, you can call ISteamClient::CreateSteamPipe() to create a communication pipe between your game and Steam client, then call ISteamClient::ConnectToGlobalUser() to get an instance of ISteamUser, which represents the current logged-in user.


Each interface in Steamworks SDK has a set of functions that perform various operations related to Steam features. For example, ISteamUser has functions like ISteamUser::GetSteamID(), which returns the unique Steam ID of the user, or ISteamUser::GetUserDataFolder(), which returns the path to the user's local data folder. You can find the documentation for all interfaces and functions in Steamworks SDK on the official website.


The concept of call results and callbacks




Many of the functions in Steamworks SDK are asynchronous, meaning that they do not return a value immediately, but instead send a request to Steam client or server and wait for a response. For example, when you call ISteamUser::RequestEncryptedAppTicket(), which requests an encrypted app ticket for the current user, the function returns a SteamAPICall_t handle, which is a unique identifier for the request, but does not return the actual app ticket. You need to wait for Steam to process your request and send you a response, which may take some time depending on the network conditions and server load.


To handle asynchronous operations, Steamworks SDK uses the concept of call results and callbacks. A call result is a way to receive the result of an asynchronous function call, while a callback is a way to receive notifications or events from Steam client or server. Both call results and callbacks are implemented as classes that inherit from CCallbackBase, which is an abstract base class that defines the common interface and behavior for all callbacks and call results.


To use a call result, you need to create an instance of a class that inherits from CCallResult, which is a template class that takes the type of the response data as a template parameter. For example, to receive the result of ISteamUser::RequestEncryptedAppTicket(), you need to create an instance of CCallResult<EncryptedAppTicketResponse_t>, where EncryptedAppTicketResponse_t is a struct that contains the response data. You also need to provide a callback function that will be called when the result is available, and pass it to the constructor of CCallResult. For example:


// Declare a CCallResult instance CCallResult<EncryptedAppTicketResponse_t> m_CallResultEncryptedAppTicket; // Define a callback function void OnEncryptedAppTicket(EncryptedAppTicketResponse_t *pEncryptedAppTicket, bool bIOFailure) // Check for errors if (bIOFailure) // Handle IO failure else if (pEncryptedAppTicket->m_eResult != k_EResultOK) // Handle result error else // Handle success // Access the response data from pEncryptedAppTicket // In your initialization code, create the CCallResult instance and pass the callback function m_CallResultEncryptedAppTicket.Set(OnEncryptedAppTicket); // In your code where you make the async function call, pass the CCallResult instance as the parameter SteamAPICall_t hSteamAPICall = SteamUser()->RequestEncryptedAppTicket(NULL, 0); m_CallResultEncryptedAppTicket.SetGameserverFlag(); // Optional: set this flag if you are running as a game server m_CallResultEncryptedAppTicket.SetCall(hSteamAPICall); // This will register the call result with Steamworks SDK


To use a callback, you need to create an instance of a class that inherits from CCallback, which is another template class that takes the type of the notification or event data as a template parameter. For example, to receive notifications about Steam inventory changes, you need to create an instance of CCallback<SteamInventoryResultReady_t>, where SteamInventoryResultReady_t is a struct that contains the notification data. You also need to provide a callback function that will be called when the notification or event occurs, and pass it to the constructor of CCallback. For example:


// Declare a CCallback instance CCallback<SteamInventoryResultReady_t> m_CallbackInventoryResultReady; // Define a callback function void OnInventoryResultReady(SteamInventoryResultReady_t *pInventoryResultReady) // Check for errors if (pInventoryResultReady->m_result != k_EResultOK) // Handle result error else // Handle success // Access the notification data from pInventoryResultReady // In your initialization code, create the CCallback instance and pass the callback function m_CallbackInventoryResultReady.Set(OnInventoryResultReady); // In your code where you want to receive notifications or events, register the CCallback instance with Steamworks SDK m_CallbackInventoryResultReady.Register(); // This will register the callback with Steamworks SDK


The main difference between call results and callbacks is that call results are associated with specific function calls, while callbacks are associated with general notifications or events that can occur at any time. For example, you can use a call result to get the result of a specific inventory request, while you can use a callback to get notified of any inventory changes that happen in the background. You can also use both call results and callbacks together, for example, by using a call result to get the initial inventory data, and then using a callback to get updates on the inventory changes.


How to use steamAPI Unregistercallresult in your code




The syntax and parameters of steamAPI Unregistercallresult




As we have seen, call results are a way to receive the result of an asynchronous function call. However, what happens if you no longer need or want to receive the result of a function call? For example, what if you cancel an inventory request, or you exit the game before the result is available? In that case, you need to use the function steamAPI Unregistercallresult to unregister the call result and free up the memory and resources associated with it.


The syntax of steamAPI Unregistercallresult is as follows:


void steamAPI_UnregisterCallResult(CCallbackBase *pCallback, SteamAPICall_t hAPICall);


The function takes two parameters: pCallback and hAPICall. pCallback is a pointer to the CCallbackBase object that represents the call result you want to unregister. hAPICall is the SteamAPICall_t handle that identifies the function call you want to unregister. You can get both of these values from the CCallResult instance that you created when you made the async function call.


For example, if you want to unregister the call result for ISteamUser::RequestEncryptedAppTicket(), you can use the following code:


// Get the CCallbackBase pointer from the CCallResult instance CCallbackBase *pCallback = m_CallResultEncryptedAppTicket.GetCallback(); // Get the SteamAPICall_t handle from the CCallResult instance SteamAPICall_t hAPICall = m_CallResultEncryptedAppTicket.GetCall(); // Call steamAPI_UnregisterCallResult with these parameters steamAPI_UnregisterCallResult(pCallback, hAPICall);


The benefits and drawbacks of using steamAPI Unregistercallresult




The main benefit of using steamAPI Unregistercallresult is that it can help you avoid memory leaks, performance issues, and errors in your code. When you register a call result with Steamworks SDK, it allocates some memory and resources to store and process the result. If you do not unregister the call result when you no longer need it, these memory and resources will not be freed up, and will accumulate over time. This can lead to memory leaks, which can cause your game to crash or run slower. It can also lead to performance issues, as Steamworks SDK will keep checking for results that are never going to arrive. It can also lead to errors, as Steamworks SDK may try to access invalid or corrupted memory or resources.


The main drawback of using steamAPI Unregistercallresult is that it can be tricky to use correctly and safely. You need to make sure that you only unregister call results that are no longer needed or wanted, and that you do not unregister call results that are still pending or in progress. You also need to make sure that you do not unregister call results that have already been unregistered by Steamworks SDK automatically. For example, Steamworks SDK will automatically unregister call results when they are completed or failed, or when your game exits or disconnects from Steam. If you try to unregister these call results manually, you may cause errors or crashes in your code.


Best practices and tips for using steamAPI Unregistercallresult effectively




When to use and when to avoid steamAPI Unregistercallresult




The general rule of thumb for using steamAPI Unregistercallresult is: use it when you need it, avoid it when you don't. Here are some scenarios and use cases where this function is useful or necessary, and some where it is not recommended or redundant.



  • Use it when:



  • You cancel an async function call before it is completed or failed. For example, if you make an inventory request but then decide to cancel it before getting the result, you should unregister the call result for that request.You change the state or context of your game that affects the async function call. For example, if you make a matchmaking request but then switch to a different game mode or lobby, you should unregister the call result for that request.



  • You want to reuse the same CCallResult instance for different async function calls. For example, if you have a global CCallResult instance that you use for various inventory requests, you should unregister the previous call result before making a new one.



  • Avoid it when:



  • The async function call is completed or failed. Steamworks SDK will automatically unregister the call result for you, so you do not need to do it manually.



  • Your game exits or disconnects from Steam. Steamworks SDK will automatically unregister all call results for you, so you do not need to do it manually.



  • You are not sure if the async function call is still pending or in progress. If you unregister a call result that is still waiting for a response, you may miss the result or cause errors in your code.



How to handle errors and exceptions with steamAPI Unregistercallresult




Another important aspect of using steamAPI Unregistercallresult is how to handle errors and exceptions that may occur when using this function. Here are some tips and best practices for handling errors and exceptions with steamAPI Unregistercallresult:



  • Always check the return value of the async function call before passing it to steamAPI Unregistercallresult. If the async function call returns k_uAPICallInvalid, which is a special value that indicates an invalid or failed function call, do not pass it to steamAPI Unregistercallresult, as it will cause an error.



  • Always check the validity of the CCallbackBase pointer before passing it to steamAPI Unregistercallresult. If the pointer is null or invalid, do not pass it to steamAPI Unregistercallresult, as it will cause an error.



  • Always use try-catch blocks when calling steamAPI Unregistercallresult, as it may throw exceptions if something goes wrong. For example, it may throw a std::invalid_argument exception if the parameters are invalid, or a std::runtime_error exception if the Steamworks SDK fails to unregister the call result. You should catch these exceptions and handle them appropriately in your code.



  • Always use debug tools and logs to check for errors and exceptions when using steamAPI Unregistercallresult. You can use the Steamworks SDK Debug Console to view the logs and messages from Steamworks SDK, or use your own debug tools and logs to track and monitor your code. You can also use the Steamworks SDK Error Codes to identify and resolve common errors and issues with Steamworks SDK.



Conclusion and FAQs




In this article, we have learned what steamAPI Unregistercallresult is, how it works, how to use it in your code, and what are the best practices and tips for using it effectively. We have seen that this function can help us avoid memory leaks, performance issues, and errors in our code by unregistering call results that are no longer needed or wanted. We have also seen that this function can be tricky to use correctly and safely, and that we need to be careful and vigilant when using it.


We hope that this article has helped you understand this function better and improve your game development skills. If you want to learn more about Steamworks SDK and its features, you can visit the official website or check out some of the resources below:



  • Steamworks SDK Documentation: The official documentation for all interfaces and functions in Steamworks SDK.



  • Steamworks SDK Examples: A collection of sample projects and code snippets that demonstrate how to use various features of Steamworks SDK.



  • Steamworks Development Forums: A community forum where you can ask questions, share ideas, and get feedback from other developers who use Steamworks SDK.



To wrap up this article, here are some FAQs that may help you with some common questions or doubts about steamAPI Unregistercallresult:



Q: Do I need to use steamAPI Unregistercallresult for every async function call I make with Steamworks SDK?


  • A: No, you do not need to use steamAPI Unregistercallresult for every async function call you make with Steamworks SDK. You only need to use it for the async function calls that return a SteamAPICall_t handle, and only if you want to unregister the call result before it is completed or failed. For the async function calls that do not return a SteamAPICall_t handle, or that you want to wait for the result, you do not need to use steamAPI Unregistercallresult.



Q: How can I tell if an async function call returns a SteamAPICall_t handle or not?


A: You can tell if an async function call returns a SteamAPICall_t handle or not by looking at the documentation or the header file of the interface that contains the function. If the function returns a SteamAPICall_t handle, it will have a return type of SteamAPICall_t, and it will have a parameter of type CSteamAPICallCompleted_t *, which is a pointer to a struct that contains the SteamAPICall_t handle. For example, the function ISteamUser::RequestEncryptedAppTicket() has the following signature:


SteamAPICall_t RequestEncryptedAppTicket( void *pUserData, int cbUserData, CSteamAPICallCompleted_t *pCallback );


If the function does not return a SteamAPICall_t handle, it will have a different return type, and it will not have a parameter of type CSteamAPICallCompleted_t *. For example, the function ISteamUser::GetAuthSessionTicket() has the following signature:


HAuthTicket GetAuthSessionTicket( void *pTicket, int cbMaxTicket, uint32 *pcbTicket );





Q: Can I use steamAPI Unregistercallresult for callbacks as well as call results?


  • A: No, you cannot use steamAPI Unregistercallresult for callbacks as well as call results. This function is only designed for unregistering call results, which are associated with specific function calls. Callbacks are associated with general notifications or events, and they are registered and unregistered differently. To register a callback, you need to use the CCallback::Register() method of the CCallback instance. To unregister a callback, you need to use the CCallback::Unregister() method of the CCallback instance.



Q: What happens if I forget to use steamAPI Unregistercallresult for a call result?


  • A: If you forget to use steamAPI Unregistercallresult for a call result, you may cause memory leaks, performance issues, and errors in your code. Steamworks SDK will keep allocating memory and resources for the call result until it is unregistered, which may consume your game's memory and CPU resources. Steamworks SDK will also keep checking for the result of the function call, which may waste your game's network bandwidth and CPU cycles. Steamworks SDK may also try to access invalid or corrupted memory or resources when processing the call result, which may cause your game to crash or behave unpredictably.



Q: What happens if I use steamAPI Unregistercallresult for a call result that has already been unregistered by Steamworks SDK?


  • A: If you use steamAPI Unregistercallresult for a call result that has already been unregistered by Steamworks SDK, you may cause errors or crashes in your code. Steamworks SDK will try to unregister the call result again, but it may fail to find or access the memory or resources associated with it, as they have already been freed up. This may cause Steamworks SDK to throw exceptions or generate error messages, which may disrupt your game's logic or user interface.



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