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The essence of the pattern is that it creates a centralized bus through which components can send and receive messages (events). The bus acts as a mediator between the components, and they can exchange messages without the need for explicit coupling with each other. Hello everyone, my name is Dmitrii Ivashchenko, and I’m a Software Engineer at MY.GAMES. In this article, we’ll talk about an enum-based event bus in Unity, which we’ll get to in just a moment. Back to the event bus pattern itself, there are several ways to implement this, but the general idea remains the same: components send messages (events) to the bus, and other components subscribe to these events and receive them. There are two main methods to implement an event system: and : Subscribe Raise // At the point where the event occurs, we call Raise
// with the event type and data
EventBus.Raise(some_event_type, arguments);

// In the handler, we subscribe to a specific type
// of events and call the OnSomeEventRaised method
EventBus.Subscribe(some_event_type, OnSomeEventRaised); Often the event type is set as a string, but there are also implementations where a class for the passed data is used as the event type: public struct BuyEvent 
{
    public int ItedId;
}

// Raising a new event
EventBus.Raise<BuyEvent>(new BuyEvent{ ItemId = 1 });

// Subscription to event
EventBus.Subscribe<BuyEvent>(OnPlayerBuy); There are also more interesting implementations where interfaces are used for subscription. The event bus can be shared across the entire code, but there may also be separate buses that differ in purpose and method of message delivery. Another interesting way to implement EventBus is Enum-based. Why enums? Using enums as event types has several advantages: Improved code readability Low overhead for Enum processing Code autocompletion in IDE, with ease of adding new types Eliminated possibility of incorrect spelling, which is the case when using strings It adds the possibility of adding extension methods to extend functionality To more easily illustrate the main principle, some details have been omitted in the code examples below. We’ll also be using the class from the library to transmit events. Instead of UniRx, any other means of storing message handlers could also be used, such as C# delegates and events. ReactiveCommand UniRx . The complete source code is available on GitHub Using an Enum as a Event Bus One way to view an is as a type of data bus, with its elements representing concrete types of events delivered by this bus: Enum // Event bus for user interface-generated events
public enum UiEvent
{
    // Event on clicking on the "buy" button 
    BuyButtonClicked,

		// Event on opening an in-game window
		ScreenOpened,

		// Event on completing the tutorial
		TutorialFinished,

    ...
} Using C# extension methods, we can add methods for sending and subscribing to events to this enum: public static class UiEventExtensions
{
    // Declare a static readonly ReactiveCommand of type UiEvent
    private static readonly ReactiveCommand<UiEvent> 
        _uiEventCommand = new ReactiveCommand<UiEvent>();
    
    // Extension method to raise a UiEvent
    public static void Raise(this UiEvent evnt)
    {
        // Execute the ReactiveCommand with the UiEvent
        _uiEventCommand.Execute(evnt);
    }
    
    // Extension method to subscribe to a UiEvent
    public static IDisposable Subscribe(this UiEvent evntType, Action action)
    {
        // Return a subscription to the ReactiveCommand, 
        // filtered by the UiEvent type
        return _uiEventCommand.Where(evnt => evnt == evntType)
                              .Subscribe(evnt => action());
    }
} Now, we can send and receive events in the game logic like so: // Raise the BuyButtonClicked event
**UiEvent.BuyButtonClicked.Raise();**

// Subscribe to the BuyButtonClicked event
var disposable = **UiEvent.BuyButtonClicked.Subscribe**(OnBuyButtonClicked);

// ...

// Unsubscribe from the event
disposable.Dispose(); To pass parameters together with an event, we’ll need an additional class that will store the event type and data. Example implementation: // This class is used to store information about a UI event
public class UiEventParam
{
    // The type of the UI event
    public UiEvent Type { get; }

    // Constructor that sets the type of the UI event
    protected UiEventParam(UiEvent type) => Type = type;

    // Get the data associated with the UI event
    public T Get<T>() => ((UiEventParam<T>) this).Data;
}

// This class is used to store data associated with a UI event
public class UiEventParam<T> : UiEventParam
{
    // The data associated with the UI event
    public readonly T Data;

    // Constructor that sets the type and data of the UI event
    public UiEventParam(UiEvent type, T data) : base(type) => Data = data;
}

public static class UiEventExtensions
{
    // Declare a static readonly ReactiveCommand of type UiEventParam
    private static readonly ReactiveCommand<UiEventParam> _uiEventParam = new ReactiveCommand<UiEventParam>();
    
    // Create a method to raise an event with a generic type
    public static void Raise<T>(this UiEvent evnt, T data) 
        // Execute the ReactiveCommand with a new UiEventParam object containing the event and data
        => _uiEventParam.Execute(new UiEventParam<T>(evnt, data));
    
    // Create a method to subscribe to an event with a generic type
    public static IDisposable Subscribe<T>(this UiEvent evntType, Action<T> action)
    {
        // Return a subscription to the ReactiveCommand, filtering for the specified event type
        return _uiEventParam
            .Where(evnt => evnt.Type == evntType)
            .Subscribe(evnt =>
                // Execute the action with the data from the UiEventParam object
                action(evnt.Get<T>()));
    }

    public static IObservable<T> Where<T>(this UiEvent evntType, Func<T, bool> predicate)
    {
        // Create an observable sequence from the UiEventParam
        var observable = _uiEventParam.Where(evnt =>
            // Check if the event type matches the given event type 
            // and the predicate returns true
            evnt.Type == evntType && predicate(evnt.Get<T>()));
        
        return observable.Select(evnt => evnt.Get<T>());
    }
} In the example above, we created the class for generalized access to the field of the class, and we also added the method that allows filtering events based on the passed data. With these changes, we can further expand the possibilities of using the event bus: UiEventParam Data UiEventParam<T> Where void ExampleOfRaising()
{
    // Raise the SetSoundVolume event with a value
    **UiEvent.SetSoundVolume.Raise(0.5f);**
}

void SubscribeOnEvents()
{
    _disposable = new CompositeDisposable
    {
        // Subscribe to the SetSoundVolume event with any value
        **UiEvent.SetSoundVolume.Subscribe<float>(OnSetVolume),**
        
        // Subscribe to the SetSoundVolume event
        // and call the OnMute method when it is raised with a value of 0f
        **UiEvent.SetSoundVolume.Where<float>(x => x == 0f).Subscribe(OnMute),**
    };
} Encapsulating network events in an enum-based bus Similarly, we can wrap any network interactions in an enum-extension, whether that’s message exchange with the backend, or anything else. Let's consider the example of the network library . We'll write a C# extension that wraps the receiving and sending of events in an enum called : Photon Unity Networking 2 NetEvent public static class NetEventExtensions
{
    // Create a new ReactiveCommand of type NetEventParam
    private static readonly ReactiveCommand<NetEventParam> 
        _netEventParam = new ReactiveCommand<NetEventParam>();

    // Extension method to raise a NetEvent with data
    public static void Raise<T>(this NetEvent evnt, T data)
    {
        // Raise the event with the data, options, and reliable send
        PhotonNetwork.RaiseEvent((byte) evnt, data, GetOptions(evnt), SendOptions.SendReliable);
    }

    // Extension method to subscribe to a NetEvent
    public static IDisposable Subscribe<T>(this NetEvent evntType, Action<T> action)
    {
        // Return a subscription to the ReactiveCommand, 
        // filtered by the event type, 
        // and call the action with the data
        return _netEventParam.Where(evnt => evnt.Type == evntType)
                             .Subscribe(evnt => action(evnt.Get<T>()));
    }
    
    // Method to be called when a PhotonEvent is received
    public static void OnPhotonEventReceived(EventData data)
    {
        // Cast the data code to a NetEvent
        var evnt = (NetEvent) data.Code;
        // Execute the ReactiveCommand with a new NetEventParam containing the event and custom data
        _netEventParam.Execute(new NetEventParam<object>(evnt, data.CustomData));
    }
} The method should be called in your class implementing the . We can now work with network events, just like we did before, with UI events: OnPhotonEventReceived Photon interface IOnEventCallback.OnEvent // Enum for network events
public enum NetEvent
{
    // Event for player state
    PlayerReady,

    // Event for client ping
    ClientPing,

    // Event for battle finish
    BattleFinish,

    // ...
}

// Method to raise the PlayerReady event
public void OnGameLoaded()
{
    // Raise the PlayerReady event with the player's ID
    **NetEvent.PlayerReady.Raise(_playerId);**
}

// Method to subscribe to the PlayerReady event
public void SomeGameManagerOnAnotherDevice()
{
    _disposable = new CompositeDisposable
    {
        // Subscribe to the PlayerReady event
        **NetEvent.PlayerReady.Subscribe<int>(OnPlayerReady)**
    };
} Other types of buses A bus can be characterized not only by the method of delivery, but also by the environment for message propagation. The above examples show buses that deliver events at runtime, but we can also identify a separate bus for editor events (in Edit and Play-mode): [InitializeOnLoad]
public static class EditorBridge
{
    // Static constructor that is called when the class is loaded
    static EditorBridge()
    {
        var disposable = new CompositeDisposable
        {
            // Subscribe to the event and log a message when it is raised
            **EditorEvent.SomeEventName.Subscribe**(() => Debug.Log("Editor event"))
        };

        // Add a handler to the EditorApplication.quitting event
        // that disposes of the CompositeDisposable
        EditorApplication.quitting += () => disposable.Dispose();
    }

    // Create a menu item in the Tools menu
    [MenuItem("Tools/Raise Test Event")]
    public static void RaiseTestEvent()
    {
        **EditorEvent.SomeEventName.Raise();**
    }
} In this case, the implementation of the and methods will not differ from . In Edit-Mode, the event bus can be used to exchange messages between different custom editors, allowing for interface updates and synchronizing data between them. Subscribe Raise UiEventExtensions Another useful type of bus is a . In the previous examples, the sent event is executed synchronously in the same frame. However, there are tasks that require time for processing but do not demand immediate execution. For such events, a separate manager is required which will check whether there is enough time in the current frame to execute the handlers, or whether to wait for the next frame: deferred execution bus public class DelayedEventsProcessor
{
    // This method is called when the game starts
    [RuntimeInitializeOnLoadMethod]
    public static async void Init()
    {
        // Create a cancellation token source
        var source = new CancellationTokenSource();
        // Store the current delta time
        var time = Time.deltaTime;

        // While the cancellation is not requested,
        // the queue is not empty
        // and the execution limit is not exceeded
        while (!source.IsCancellationRequested 
               && !DelayedEventsQueue.IsEmpty()
               && (Time.deltaTime - time) > ExecutionLimit)
        {
            // Process the events in the queue
            DelayedEventsQueue.ProcessEvents();
            // Waiting for next frame
            await Task.Yield();
            // Update the delta time
            time = Time.deltaTime;
        }
        
        // When the application is quitting, cancel the token
        Application.quitting += () => source.Cancel();
    }
} One can separately highlight the bus, and its events will only be handled in development builds and will be turned off in release configurations. DebugEvent Pros and cons of event buses Using the event bus pattern improves Unity game architecture, simplifies development and maintenance, and enhances flexibility and performance. Let’s look in more detail: : The Event Bus pattern allows for the separation of game logic into components, which simplifies its understanding and maintenance. Each component can process only the events it needs, reducing coupling and increasing system flexibility. Separation of logic : Using an event bus makes it easy to add and remove components, simplifying game expansion and functionality changes. Flexibility : Events processed through the bus can be called asynchronously, improving game performance and reducing the likelihood of delays in operation. Asynchronicity : The event bus pattern can be used to create plugins and modules that can be easily integrated into the game. Extensibility However, it should be remembered that the Event Bus can also lead to some negative effects: : events that are processed through the bus can be triggered asynchronously, which makes it difficult to debug the application. Worsening of debugging : if event processing is not organized correctly, unpredictable interaction between components may occur, leading to errors and failures. Loss of flow control : code that uses the event bus may be harder to understand and maintain, as different components may be subscribed to the same event. Increased code complexity : transmitting messages through the bus can increase the delay in application operation, as events must be processed at the other end of the bus. Increased message transmission delay Conclusion We’ve learned how to use enums to mark data buses and message types, and have explored how to wrap event buses transmitted in different ways and in different environments with enums. Putting it all together, we can use this approach to uniformly handle any type of event, thereby improving code readability and comprehension. public void Initialize()
{
    _disposable = new CompositeDisposable
    {
        // Uniform subscription to events 
        // incoming from different buses

        **UiEvent.ExitBattleClick**.Subscribe(OnExitBattleClick),   

        **BackendEvent.BattleReset**.Subscribe(OnBattleReset),

        **DelayedEvent.ChangeWindDirection**.Subscribe<Direction>(OnChangeWindDirection),

        **NetEvent.PlayerReady**.Subscribe<PlayerReadyData>(OnPlayerReady),

        **DebugEvent.KillOpponentUnits**.Subscribe(OnKillOpponentUnits),

        **EditorEvent.SelectScene**.Subscribe<string>(OnEditorSelectScene),
    };
} To recap once more: the event bus pattern has several advantages, such as reducing the coupling between components, more flexible and extensible code, and the ability to handle messages asynchronously. However, its use can lead to code complexity and increase the difficulty of debugging the application. Therefore, before using the pattern, it is necessary to carefully evaluate its necessity and advantages in a specific project. . Source code is available on GitHub

Using an Enum-Based Event Bus Pattern In Unity

The Return of Tarzan by Edgar Rice Burroughs, is part of the HackerNoon Books Series. You can jump to any chapter in this book here . The Fight in the Desert The Fight in the Desert As the three squatted upon the roof above the quarters of the Ouled-Nails they heard the angry cursing of the Arabs in the room beneath. Abdul translated from time to time to Tarzan. “They are berating those in the street below now,” said Abdul, “for permitting us to escape so easily. Those in the street say that we did not come that way—that we are still within the building, and that those above, being too cowardly to attack us, are attempting to deceive them into believing that we have escaped. In a moment they will have fighting of their own to attend to if they continue their brawling.” Presently those in the building gave up the search, and returned to the café. A few remained in the street below, smoking and talking. Tarzan spoke to the girl, thanking her for the sacrifice she had made for him, a total stranger. “I liked you,” she said simply. “You were unlike the others who come to the café. You did not speak coarsely to me—the manner in which you gave me money was not an insult.” “What shall you do after tonight?” he asked. “You cannot return to the café. Can you even remain with safety in Sidi Aissa?” “Tomorrow it will be forgotten,” she replied. “But I should be glad if it might be that I need never return to this or another café. I have not remained because I wished to; I have been a prisoner.” “A prisoner!” ejaculated Tarzan incredulously. “A slave would be the better word,” she answered. “I was stolen in the night from my father’s douar by a band of marauders. They brought me here and sold me to the Arab who keeps this café. It has been nearly two years now since I saw the last of mine own people. They are very far to the south. They never come to Sidi Aissa.” “You would like to return to your people?” asked Tarzan. “Then I shall promise to see you safely so far as Bou Saada at least. There we can doubtless arrange with the commandant to send you the rest of the way.” “Oh, m’sieur,” she cried, “how can I ever repay you! You cannot really mean that you will do so much for a poor Ouled-Nail. But my father can reward you, and he will, for is he not a great sheik? He is Kadour ben Saden.” “Kadour ben Saden!” ejaculated Tarzan. “Why, Kadour ben Saden is in Sidi Aissa this very night. He dined with me but a few hours since.” “My father in Sidi Aissa?” cried the amazed girl. “Allah be praised then, for I am indeed saved.” “Hssh!” cautioned Abdul. “Listen.” From below came the sound of voices, quite distinguishable upon the still night air. Tarzan could not understand the words, but Abdul and the girl translated. “They have gone now,” said the latter. “It is you they want, m’sieur. One of them said that the stranger who had offered money for your slaying lay in the house of Akmed din Soulef with a broken wrist, but that he had offered a still greater reward if some would lay in wait for you upon the road to Bou Saada and kill you.” “It is he who followed m’sieur about the market today,” exclaimed Abdul. “I saw him again within the café—him and another; and the two went out into the inner court after talking with this girl here. It was they who attacked and fired upon us, as we came out of the café. Why do they wish to kill you, m’sieur?” “I do not know,” replied Tarzan, and then, after a pause: “Unless—” But he did not finish, for the thought that had come to his mind, while it seemed the only reasonable solution of the mystery, appeared at the same time quite improbable. Presently the men in the street went away. The courtyard and the café were deserted. Cautiously Tarzan lowered himself to the sill of the girl’s window. The room was empty. He returned to the roof and let Abdul down, then he lowered the girl to the arms of the waiting Arab. From the window Abdul dropped the short distance to the street below, while Tarzan took the girl in his arms and leaped down as he had done on so many other occasions in his own forest with a burden in his arms. A little cry of alarm was startled from the girl’s lips, but Tarzan landed in the street with but an imperceptible jar, and lowered her in safety to her feet. She clung to him for a moment. “How strong m’sieur is, and how active,” she cried. “El Adrea, the black lion, himself is not more so.” “I should like to meet this el Adrea of yours,” he said. “I have heard much about him.” “And you come to the douar of my father you shall see him,” said the girl. “He lives in a spur of the mountains north of us, and comes down from his lair at night to rob my father’s douar. With a single blow of his mighty paw he crushes the skull of a bull, and woe betide the belated wayfarer who meets el Adrea abroad at night.” Without further mishap they reached the hotel. The sleepy landlord objected strenuously to instituting a search for Kadour ben Saden until the following morning, but a piece of gold put a different aspect on the matter, so that a few moments later a servant had started to make the rounds of the lesser native hostelries where it might be expected that a desert sheik would find congenial associations. Tarzan had felt it necessary to find the girl’s father that night, for fear he might start on his homeward journey too early in the morning to be intercepted. They had waited perhaps half an hour when the messenger returned with Kadour ben Saden. The old sheik entered the room with a questioning expression upon his proud face. “Monsieur has done me the honor to—” he commenced, and then his eyes fell upon the girl. With outstretched arms he crossed the room to meet her. “My daughter!” he cried. “Allah is merciful!” and tears dimmed the martial eyes of the old warrior. When the story of her abduction and her final rescue had been told to Kadour ben Saden he extended his hand to Tarzan. “All that is Kadour ben Saden’s is thine, my friend, even to his life,” he said very simply, but Tarzan knew that those were no idle words. It was decided that although three of them would have to ride after practically no sleep, it would be best to make an early start in the morning, and attempt to ride all the way to Bou Saada in one day. It would have been comparatively easy for the men, but for the girl it was sure to be a fatiguing journey. She, however, was the most anxious to undertake it, for it seemed to her that she could not quickly enough reach the family and friends from whom she had been separated for two years. It seemed to Tarzan that he had not closed his eyes before he was awakened, and in another hour the party was on its way south toward Bou Saada. For a few miles the road was good, and they made rapid progress, but suddenly it became only a waste of sand, into which the horses sank fetlock deep at nearly every step. In addition to Tarzan, Abdul, the sheik, and his daughter were four of the wild plainsmen of the sheik’s tribe who had accompanied him upon the trip to Sidi Aissa. Thus, seven guns strong, they entertained little fear of attack by day, and if all went well they should reach Bou Saada before nightfall. A brisk wind enveloped them in the blowing sand of the desert, until Tarzan’s lips were parched and cracked. What little he could see of the surrounding country was far from alluring—a vast expanse of rough country, rolling in little, barren hillocks, and tufted here and there with clumps of dreary shrub. Far to the south rose the dim lines of the Saharan Atlas range. How different, thought Tarzan, from the gorgeous Africa of his boyhood! Abdul, always on the alert, looked backward quite as often as he did ahead. At the top of each hillock that they mounted he would draw in his horse and, turning, scan the country to the rear with utmost care. At last his scrutiny was rewarded. “Look!” he cried. “There are six horsemen behind us.” “Your friends of last evening, no doubt, monsieur,” remarked Kadour ben Saden dryly to Tarzan. “No doubt,” replied the ape-man. “I am sorry that my society should endanger the safety of your journey. At the next village I shall remain and question these gentlemen, while you ride on. There is no necessity for my being at Bou Saada tonight, and less still why you should not ride in peace.” “If you stop we shall stop,” said Kadour ben Saden. “Until you are safe with your friends, or the enemy has left your trail, we shall remain with you. There is nothing more to say.” Tarzan nodded his head. He was a man of few words, and possibly it was for this reason as much as any that Kadour ben Saden had taken to him, for if there be one thing that an Arab despises it is a talkative man. All the balance of the day Abdul caught glimpses of the horsemen in their rear. They remained always at about the same distance. During the occasional halts for rest, and at the longer halt at noon, they approached no closer. “They are waiting for darkness,” said Kadour ben Saden. And darkness came before they reached Bou Saada. The last glimpse that Abdul had of the grim, white-robed figures that trailed them, just before dusk made it impossible to distinguish them, had made it apparent that they were rapidly closing up the distance that intervened between them and their intended quarry. He whispered this fact to Tarzan, for he did not wish to alarm the girl. The ape-man drew back beside him. “You will ride ahead with the others, Abdul,” said Tarzan. “This is my quarrel. I shall wait at the next convenient spot, and interview these fellows.” “Then Abdul shall wait at thy side,” replied the young Arab, nor would any threats or commands move him from his decision. “Very well, then,” replied Tarzan. “Here is as good a place as we could wish. Here are rocks at the top of this hillock. We shall remain hidden here and give an account of ourselves to these gentlemen when they appear.” They drew in their horses and dismounted. The others riding ahead were already out of sight in the darkness. Beyond them shone the lights of Bou Saada. Tarzan removed his rifle from its boot and loosened his revolver in its holster. He ordered Abdul to withdraw behind the rocks with the horses, so that they should be shielded from the enemies’ bullets should they fire. The young Arab pretended to do as he was bid, but when he had fastened the two animals securely to a low shrub he crept back to lie on his belly a few paces behind Tarzan. The ape-man stood erect in the middle of the road, waiting. Nor did he have long to wait. The sound of galloping horses came suddenly out of the darkness below him, and a moment later he discerned the moving blotches of lighter color against the solid background of the night. “Halt,” he cried, “or we fire!” The white figures came to a sudden stop, and for a moment there was silence. Then came the sound of a whispered council, and like ghosts the phantom riders dispersed in all directions. Again the desert lay still about him, yet it was an ominous stillness that foreboded evil. Abdul raised himself to one knee. Tarzan cocked his jungle-trained ears, and presently there came to him the sound of horses walking quietly through the sand to the east of him, to the west, to the north, and to the south. They had been surrounded. Then a shot came from the direction in which he was looking, a bullet whirred through the air above his head, and he fired at the flash of the enemy’s gun. Instantly the soundless waste was torn with the quick staccato of guns upon every hand. Abdul and Tarzan fired only at the flashes—they could not yet see their foemen. Presently it became evident that the attackers were circling their position, drawing closer and closer in as they began to realize the paltry numbers of the party which opposed them. But one came too close, for Tarzan was accustomed to using his eyes in the darkness of the jungle night, than which there is no more utter darkness this side the grave, and with a cry of pain a saddle was emptied. “The odds are evening, Abdul,” said Tarzan, with a low laugh. But they were still far too one-sided, and when the five remaining horsemen whirled at a signal and charged full upon them it looked as if there would be a sudden ending of the battle. Both Tarzan and Abdul sprang to the shelter of the rocks, that they might keep the enemy in front of them. There was a mad clatter of galloping hoofs, a volley of shots from both sides, and the Arabs withdrew to repeat the maneuver; but there were now only four against the two. For a few moments there came no sound from out of the surrounding blackness. Tarzan could not tell whether the Arabs, satisfied with their losses, had given up the fight, or were waiting farther along the road to waylay them as they proceeded on toward Bou Saada. But he was not left long in doubt, for now all from one direction came the sound of a new charge. But scarcely had the first gun spoken ere a dozen shots rang out behind the Arabs. There came the wild shouts of a new party to the controversy, and the pounding of the feet of many horses from down the road to Bou Saada. The Arabs did not wait to learn the identity of the oncomers. With a parting volley as they dashed by the position which Tarzan and Abdul were holding, they plunged off along the road toward Sidi Aissa. A moment later Kadour ben Saden and his men dashed up. The old sheik was much relieved to find that neither Tarzan nor Abdul had received a scratch. Not even had their horses been wounded. They sought out the two men who had fallen before Tarzan’s shots, and, finding that both were dead, left them where they lay. “Why did you not tell me that you contemplated ambushing those fellows?” asked the sheik in a hurt tone. “We might have had them all if the seven of us had stopped to meet them.” “Then it would have been useless to stop at all,” replied Tarzan, “for had we simply ridden on toward Bou Saada they would have been upon us presently, and all could have been engaged. It was to prevent the transfer of my own quarrel to another’s shoulders that Abdul and I stopped off to question them. Then there is your daughter—I could not be the cause of exposing her needlessly to the marksmanship of six men.” Kadour ben Saden shrugged his shoulders. He did not relish having been cheated out of a fight. The little battle so close to Bou Saada had drawn out a company of soldiers. Tarzan and his party met them just outside the town. The officer in charge halted them to learn the significance of the shots. “A handful of marauders,” replied Kadour ben Saden. “They attacked two of our number who had dropped behind, but when we returned to them the fellows soon dispersed. They left two dead. None of my party was injured.” This seemed to satisfy the officer, and after taking the names of the party he marched his men on toward the scene of the skirmish to bring back the dead men for purposes of identification, if possible. Two days later, Kadour ben Saden, with his daughter and followers, rode south through the pass below Bou Saada, bound for their home in the far wilderness. The sheik had urged Tarzan to accompany him, and the girl had added her entreaties to those of her father; but, though he could not explain it to them, Tarzan’s duties loomed particularly large after the happenings of the past few days, so that he could not think of leaving his post for an instant. But he promised to come later if it lay within his power to do so, and they had to content themselves with that assurance. During these two days Tarzan had spent practically all his time with Kadour ben Saden and his daughter. He was keenly interested in this race of stern and dignified warriors, and embraced the opportunity which their friendship offered to learn what he could of their lives and customs. He even commenced to acquire the rudiments of their language under the pleasant tutorage of the brown-eyed girl. It was with real regret that he saw them depart, and he sat his horse at the opening to the pass, as far as which he had accompanied them, gazing after the little party as long as he could catch a glimpse of them. Here were people after his own heart! Their wild, rough lives, filled with danger and hardship, appealed to this half-savage man as nothing had appealed to him in the midst of the effeminate civilization of the great cities he had visited. Here was a life that excelled even that of the jungle, for here he might have the society of men—real men whom he could honor and respect, and yet be near to the wild nature that he loved. In his head revolved an idea that when he had completed his mission he would resign and return to live for the remainder of his life with the tribe of Kadour ben Saden. Then he turned his horse’s head and rode slowly back to Bou Saada. The front of the Hotel du Petit Sahara, where Tarzan stopped in Bou Saada, is taken up with the bar, two dining-rooms, and the kitchens. Both of the dining-rooms open directly off the bar, and one of them is reserved for the use of the officers of the garrison. As you stand in the barroom you may look into either of the dining-rooms if you wish. It was to the bar that Tarzan repaired after speeding Kadour ben Saden and his party on their way. It was yet early in the morning, for Kadour ben Saden had elected to ride far that day, so that it happened that when Tarzan returned there were guests still at breakfast. As his casual glance wandered into the officers’ dining-room, Tarzan saw something which brought a look of interest to his eyes. Lieutenant Gernois was sitting there, and as Tarzan looked a white-robed Arab approached and, bending, whispered a few words into the lieutenant’s ear. Then he passed on out of the building through another door. In itself the thing was nothing, but as the man had stooped to speak to the officer, Tarzan had caught sight of something which the accidental parting of the man’s burnoose had revealed—he carried his left arm in a sling. About HackerNoon Book Series: We bring you the most important technical, scientific, and insightful public domain books. This book is part of the public domain. Edgar Rice Burroughs (1993). The Return of Tarzan. Urbana, Illinois: Project Gutenberg. Retrieved October 2022 https://www.gutenberg.org/cache/epub/81/pg81-images.html This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org , located at https://www.gutenberg.org/policy/license.html .

The Fight in the Desert

This article is about proxygen - a library used to build all kinds of servers. It is open-sourced and maintained by Meta. Initially, framework was envisaged as a collection of tools used to develop proxies. Hence proxygen. However, this library is so much more. In the first article in this series, we will go through developing the most simple HTTP client possible. There are a lot of moving pieces so I prefer to keep complexity to a minimum and only focus on what is important. If you’re reading this, you probably have a good head on your shoulders and you will be able to expand on this on your own. First, let’s start with very general proxygen architecture. Data is either read from a socket or written to a socket. We then have that uses to read/write data to/from the socket. Each will have one or more . Each interacts with a Handler as data is received/sent. You can see this illustrated in the image below. HTTPSession HTTPCodec HTTPSession HTTPTransactions HTTPTransaction This very simple, yet powerful set of abstractions allows handling all sorts of  other protocols like HTTP2, HTTP3/QUIC/SPDY including own “home” grown protocols. But before you start working with any of these you’ll probably want to build the most basic application to make sure the project is set up correctly and that you understand all relevant concepts. I personally found this to be the most challenging part. Even though proxygen comes with it’s own build script and a set of examples, I didn’t find this the most “friendly”. Porxygen relies heavily on some other libraries (e.g. folly, libevent, glog, gflags…) so you will need to make sure that those are present on your system too. You might also want to customize which compiler and/or linker is used. I personally like to use clang compiler and toolset that comes with it. In order to help with the above problems, I created a repository that does the following: introduces most dependencies as git submodules provides a build script to build all dependencies implements a simple HTTP client (KissClient, Kiss stands for eep t tupid imple) k i s s provides instructions how to build the client Caveat: the project currently only works on linux. At the moment I don’t have plans to make it work on MacOS X or Windows. Having said that, I am open to accepting a pull request. This repository should be enough for you to fork and go make your own project based on proxygen. If you run into any problems, please open an issue ( ) or reach out via discord ( ) https://gitlab.com/technologysoup/starter-kits/hello-proxygen/-/issues https://discord.gg/vFbZFzMmDK Now let’s walk through the example. I strongly suggest you open code and  reference it as you read the rest. The code is available in git repo: https://gitlab.com/technologysoup/starter-kits/hello-proxygen/-/tree/main/src/kiss_client is the class where we implement the client. It extends two other classes - and . KissClient proxygen::HTTPConnector::Callback proxygen::HTTPTransactionHandler is used to establish new HTTP or HTTPS connections while defines callback object which will receive results. The callback object has and methods. proxygen::HTTPConnector proxygen::HTTPConnector::Callback connectSuccess connectError represents one request/response pair in an HTTP-like protocol. It works with a Transport and a Handler to handle ingress and egress of data. HTTPTransaction When a session is established will be called with a session object which in turn is  used to get a new .  That transaction object ( ) is used to send headers and body. connectSuccess HTTPTransaction txn_ Once the client finishes sending content (headers + body), server will send a response. At that point hooks which are implemented as part of interface will be called - , , ,etc. HTTPTransactionHandler onHeadersComplete onBody onEOM To summarize, the sequence of events is: The application creates a and a object. callback handler The application then creates passing it the and connects to an address. HTTPConnector callback Once the connection is successfully established an is created using the hooks. HTTPSession callback The session is used to create a new . The is initialized using object. HTTPTransaction HTTPTransaction handler The transaction is used to send request to server. Once the server response is received hooks are invoked. handler When the session goes idle (meaning there is nothing more to  exchange between client and server) the is closed. session And that is it. We have a working HTTP client. You can test it by spinning up some server or using netcat. $ ./hello-proxygen
I0606 23:00:19.731132 1463353 kiss_client.cc:44] Sending request for http://localhost:4586
I0606 23:00:19.731266 1463353 kiss_client.cc:21] Got headers for http://localhost:4586.
I0606 23:00:19.731276 1463353 kiss_client.cc:24] Got body for http://localhost:4586.
I0606 23:00:19.731279 1463353 kiss_client.cc:31] Got EOM for http://localhost:4586. In my next article, I plan to show how to make a simple HTTP server. If you have any questions feel free to drop a comment below.

Building a Simple HTTP Client Using Proxygen

Android SDK provides APIs for most of the common work which a developer uses every day like , , and so on.Sometimes we might need to work on low-level functionality which mostly are available as .With NDK we can use these pre-built libraries by creating a C/C++ wrapper around it and the use JNI to invoke the native code from Kotlin/Java. direct share app linking fingerprint authentication C/C++ libraries Android Through this article I will be explaining How to integrate pre-built libraries with Android app e.g. FFmpeg Create a wrapper around the pre-built library to use with your android application. For information on NDK basics and callbacks from native code you can look into my previous articles : Android NDK:Using Kotlin Episode 1- The Concepts Android NDK:Using Kotlin Episode 2- Callbacks(kotlin to cpp) Android NDK:Using Kotlin Episode 3- Callbacks continued. Integrating FFmpeg with Android application For one of the projects there was a requirement to use FFmpeg for video processing.Being new to using FFmpeg I came across remuxing, transcoding, transrating and the transsizing process which are required to process videos. Remuxing Remuxing is a lossless process that is used to change the container format of a given file(e.g. mp4 to avi or vice versa). Remuxing Transcoding is the process of converting a file from one encoding format to another so that the content can be viewed on different playback devices. Transcoding Transcoding Transrating Transrating is the process by which video files and audio files are converted to a reduced bit rate while still maintaining the original media format. Transsizing Transsizing refers to changing the picture size of video, and is useful if the output resolution differs from the resolution of the media. Depending on the requirements one can choose remuxing or transcoding. For example: To convert one format to another — Remuxing To crop a video or play live streams — Transcoding To reduce bit rates — Transrating To change resolution — Transsizing Often these methods are used in combination to obtain the desired results Compiling FFmpeg for Android Here comes the important part i.e. compiling the FFmpeg source code to generate libraries for android( ). Having worked with some of the hardware related projects helped me a lot as the terminology was not sounding alien to me anymore 😛. Here are some of the tutorials I followed to generate the libraries. Cross- Compilation Compile FFmpeg for android. Compile X264 for android. These tutorials will help you through the hurdle of cross compilation. After compilation you will have the as shown below: ABIs FFmpeg Library There are two kinds of in C/C++ libraries Shared: Shared libraries are files.All the code related to the library is in this file, and it is referenced by programs using it at run-time. .so A program using a shared library only makes reference to the code that it uses in the shared library. Static:Static libraries are the .a files.All the code related to the library is in this file, and it is directly linked into the program at compile time. A program using a static library takes copies of the code that it uses from the static library and makes it part of the program. FFmpeg contains a set of shared libraries which can be used for different operations: : provides a generic encoding/decoding framework and contains multiple decoders and encoders for audio, video and subtitle streams, and several bitstream filters. [libavcodec](https://www.ffmpeg.org/libavcodec.html) : is a utility library to aid portable multimedia programming. [libavutil](https://www.ffmpeg.org/libavutil.html) : provides a generic framework for multiplexing and demultiplexing (muxing and demuxing) audio, video and subtitle streams. [libavformat](https://www.ffmpeg.org/libavformat.html) : provides a generic framework for grabbing from and rendering to many common multimedia input/output devices, and supports several input and output devices, including Video4Linux2, VfW, DShow, and ALSA. [libavdevice](https://www.ffmpeg.org/libavdevice.html) : provides a generic audio/video filtering framework containing several filters, sources and sinks. [libavfilter](https://www.ffmpeg.org/libavfilter.html) : is a library that handles audio resampling, sample format conversion and mixing. [libavresample](https://www.ffmpeg.org/doxygen/2.5/group__lavr.html) : this library performs highly optimized image scaling and colorspace and pixel format conversion operations. [libswscale](https://www.ffmpeg.org/libswscale.html) : this library performs highly optimized audio resampling, rematrixing and sample format conversion operations. [libswresample](https://www.ffmpeg.org/libswresample.html) : is a post processing library for use in transcode. libpostproc Depending on the project requirements one can choose the libraries required to be integrated in the project. Adding Compiled Libraries to your Project You can include the libraries under the JNI folder as below depending on the requirements: Adding Shared Libs and header files to project Add this to CMakeLists.txt file Creating a wrapper to work with the Libraries As we have added the FFmpeg libraries to the project and linked the to the FFmpeg libraries using , we can now use the available functions from the libraries by including the header files in * . JNIFunctions.cpp target_link_libraries .h Here is one of the functions which get the SPS(Sequence Parameter Set) frames from the RTSP feed: Conclusion FFmpeg is an awesome library for A/V processing.We can perform demuxing, rotation of display matrix, video cropping, merging audio and video streams etc. There are lot of projects using FFmpeg library.Do hop into them for more information. open Source If you liked this post, hit 👏 . Special thanks to my friend and colleague for pushing me to write this article. Arun Sasidharan Catch me here: _LinkedIn:_ Twitter: @iamnitishbhatt https://www.linkedin.com/in/iamnitishbhatt/ Github: https://github.com/initishbhatt

My Experience with FFmpeg on Android

The topic of 1% keeps resonating because its both tantalizing to the masses but also very divisive. As Apple launches the latest iPhone priced even higher than earlier Apple phones, its a good time to revisit why that makes a great strategy. Apple has launched yet another product that many critics call over-priced and focused on the 1%. I posit in this blog post that that is an excellent product strategy. Apple Watch Edition: The Gold Watch for the 1% of the 1% There are some very interesting startups that are taking the technology to the masses and solving problems for . The mobile phone has allowed innovations like mCommerce to reach banking and healthcare where not earlier possible. the bottom of the pyramid But I believe that often times, the right answer for an entrepreneur is to do the exact opposite and in stead focus on the relatively wealthy. In fact, innovations like iPhone started out by solving a problem at a price point that could only be afforded by the relatively wealthy. Same for Tesla. And August. Car for the Rich Elites. The 1%. Let’s look at why this seems to work so well, and for what kind of innovations. One way to imagine what goods and services we all will have access to two to three years out is to look at what the relatively rich are doing today. Electric cars are going to be affordable for all as Tesla builds scale and moves down market and competitors license its technology or build their own versions. We will all get access to slim Macbook Air like computers in years to come as it becomes the industry de facto. Innovation at the Top of the Pyramid — The Future is Rich and Lives in Kansas The Lock Suitable for Kings. Only $199 for a lock. As an entrepreneur, you can essentially project into the ‘future’ by catering to the needs of those who ‘live’ in the future — due to their ability to spend more. In fact, income is just one way to project into the future — you can also target certain geographies. For example, cities with , and high bandwidth wireless cities in Korea and Japan where the future has arrived early. When you build a product that meets the needs of these ‘future cities’ and ‘future people’, you are solving a problem that will eventually be relevant to the masses and you would have multi year lead over your competitors. Google Fiber in US Well, we all know that this is not a true statement in the literal. But if you look at how even the modest among live today, we have a life style that would be the envy of the rich from a few decades ago — airconditioning was rare, access to good entertainment (or any entertainment) was rare, travel was difficult and slow, beds had bugs and no one was immune to the diseases we all have magical immunity to today thanks to vaccine and antibacterial drugs. You don’t have to go 100 years back to feel good. Just compare what you and I can do with a modest smartphone today compared to even 10 years ago. In the Future, Everyone is Rich (Metaphorically Speaking) The Moore’s law and its partners — have essentially lowered the cost of access to all kinds of amazing innovations and inventions. Essentially rendering us rich. Just yesterday, I was interrupted by a minimum wage security guard who was just doing his job — by taking pictures of the shared BBQ areas on his Android phone with an app to do his job! What this means to you in practical terms is — if you build the product at a price point that is only accessible for the relatively rich, your product over time should get cheaper and become accessible to a much larger market. I believe this will be true of over-priced connected locks, of personalized medicine, of 3D printing, of driverless cars, of learning thermostats and so many more amazing innovations. They all look a bit expensive today — even outrageous when you compare them to their mass produced competitors. But its easier for prices to magically go down (scale & time do that) than it is for your low end product to magically become better (never happens on its own). The income gains of last few decades have all gone to the relative few.The number of households making more than $100K in the US has actually gone up a lot in the last 20 years. So while our median household income is not rising as fast at least here in the US, the number of high income households is exploding. The rich though are getting created through income growth not exactly reproduction — in fact, the fertility rates go down as incomes go up. The Rich are Multiplying like Rabbits Now if you take into account the new millionaires in China and India, the number of people worldwide with high net worth and high disposable incomes is growing very rapidly as pointed out by this . BCG report We have an opportunity to build products that meet the needs of the affluent mass market. Just as Starbucks raised the average price of coffee from less than a dollar to three to five dollars, the affluent are happy to spend money on products that deliver value. In technology, we can see this in how how well products from Apple do — not just in volume (which is respectable) but more importantly in profitability. To me, the following products represent the products that meet the ‘needs’ of the affluent mass market.- Apple iPhone- Apple iPad- Starbucks- Tesla (early and at the top end)- Prius- Organic foods (we all want good food, only some of us can afford it) — see - The Trunk Club China Consider building products that may only seem to appeal to those that may be making $250K per year or more. Or if you want to go little more mass affluent, target household income of $100K which in places outside of San Francisco and New York still gets you a lot of disposable income. Target: $250K What would you build if you focused on the rich?- Better rental car service? Like Silvercar.com- Better travel service?- Better air travel? NetJets.com? Clearme.com?- Home health care? OneMedical.com? Concierge medical service?- More devices connected to my body?- Better Sleep? Sleep Number bed? Foam?- Faster internet? Google Fiber- Better locks?- Better Baby Monitors? The best part about this is you can now think in a new constraint. (No constraint is usually a bad idea). Take the products you don’t like and think what you could build for 2 to 10x the price!

Forget the Poor, Build it for the 1%

Part 1: Intro Check it out: 10 000%+ returns, ~5% drawdown on TradingView! https://www.tradingview.com/chart/XBTUSD/FkIqJJcy-Introducing-Neomenia/ With humble beginnings as a paid project by @Patrick2018, a community member with a vision, and throughout countless evolutions and 81 git commits - our baby Neomenia Bot is ready for consumption by the general public. We have had seen considerable success with different config vars over tiem, and now we even supply the most optimized vars according to market condition via a RESTful interface that provides the vars to client apps. We have packaged Windows, Linux and Mac apps for BTCUSDT on Binance, ETHUSDT, and a balance-reporting site of your own like the one below: Start: Sat Nov 30 2019 14:21:06 GMT+0000 (UTC) Now: Sun Dec 01 2019 05:17:39 GMT+0000 (UTC) BTC Notional traded recent memory: 38.44400000000188 Current position: -1.952 BTC % Delta: 31.89% BTC % ROI / day projected: 51.22% BTC % APR projected: 1.869e+4% http://neomeniab1.duckdns.org Part 2: Affiliate Program Know loads of people that would appreciate consistent deltas? Join our Telegram room (link below..) and earn a hefty % of our $ we earn when you refer us paying clients. Moreover - earn that same % when they renew in following months, building an income stream for yourself that's evergreen and passive! Part 3: How to Participate? Did I pique your interest? Read on.... Steps to Reproduce Step 1. Join our Telegram https://t.me/joinchat/G3tz4RdZGmNdxs9vXdum7A Step 2. Create a net-new Binance account, and enable futures, and create an api key after enabling futures http://www.binance.com/en/register?ref=27039658, You’re allowed to have as many Binance accounts as you like, while only verifying one – the max daily withdrawal on an unverified account is still huge Step 3: Sent the subscription fee to our wallet 0x55FC78F760fBeb15A8a14ce2B8e9DCfA4CE0f966 Step 4: Enter your transaction ID on this form. Step 5: And the last 6 characters of your API key. Step 6: The team will manually add you to the bot’s license, and send you the executable file and other directions. Step 7: Run the appropriate exports or setx’s from within env.sh. DO NOT simply run env.sh, it won’t work, copy and paste the commands into a terminal/cmd window. On windows, open a net new cmd when finished. Step 8: Run the executable for app for BTCUSDT, eth for ETHUSDT, and balance for a balance output graph like the ones you’re used to seeing. Neomenia FAQs FAQ 1: Settings variables with ‘eth’ prepended are the same, for the ethusdt bot delaybetweenorder, higher for more delay before a new limit order takeProfit, in % what gains to lock in before market out stopLoss, in % what losses to accept before market out tgUser, your Telegram username for use with the Telegram bot key, APIkey secret, APIsecret Note that the key and secret are never communicated anywhere off the local machine, except in signed requests to the exchange (which hide your details). Wireshark sniffing can confirm this. site, the http or https address where your server is located. You can google curl ipify to find your address if you’re in a headless server, or google ‘what is my ip’ if you have an interface. You can set up DNS forwarding on duckdns.org or register your own spiffy shiny new domain if you like. poirt, which port to run the balance server on. Use 80 for http 443 for https (which isn’t enabled anyhow) or a higher number like 8080 if you’re having permissions issues. maxFreePerc, what maximum % of the wallet will be used before stopping ordering in the same direction. Note this doesn’t count existing limit orders, which could max our margin if your delay is too small. orderSizeMult, for a $50 USDT account use 5, for $250 use 1, for $500 use 0.5. Etc. FAQ 2: Legal Mumbo Jumbo In no way are our team or any affiliated member responsible for any gains or losses you might experience. Previous action is no indication implied or assured of future performance. Risk only what you can afford to lose. This bot does not constitute financial advice by any means, and is meant to be used in an educational, communal, and fun format. Sign Up Now! https://forms.gle/hWa7uzZFg9nD1khg8 Join our Telegram! https://t.me/joinchat/G3tz4RdZGmNdxs9vXdum7A

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