IEventLoop.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "EventLoop/EventLoopTimer.h"
#include "Misc/Timespan.h"
#include "Templates/Function.h"
#include "Templates/SharedPointer.h"
 
namespace UE::EventLoop {
 
class IRequestManager;
 
enum class EEventLoopStatus : uint8
{
    Unintialized,
    Running,
    Terminated,
};
 
using FAsyncTask = TUniqueFunction<void()>;
using FOnShutdownComplete = TUniqueFunction<void()>;
 
class IEventLoop : public TSharedFromThis<IEventLoop, ESPMode::ThreadSafe>
{
public:
    virtual ~IEventLoop() = default;
 
    virtual bool Init() = 0;
 
    virtual void RequestShutdown(FOnShutdownComplete&& OnShutdownComplete = FOnShutdownComplete()) = 0;
 
    virtual FTimerHandle SetTimer(FTimerCallback&& Callback, FTimespan InRate, bool InbRepeat = false, TOptional<FTimespan> InFirstDelay = TOptional<FTimespan>()) = 0;
 
    virtual void ClearTimer(FTimerHandle& InHandle, FOnTimerCleared&& OnTimerCleared = FOnTimerCleared()) = 0;
 
    virtual void PostAsyncTask(FAsyncTask&& Task) = 0;
 
    /*
     * Run the event loop until shutdown is called.
     * The event loop will wake up when a timer needs to run or an async task has been posted.
     * 
     * NOT thread safe.
     */
    virtual void Run() = 0;
 
    /*
     * Run one iteration of the event loop.
     * 
     * NOT thread safe.
     * 
     * @param WaitTime Maximum amount of time to wait for events.
     * @return true if RunOnce should be called again.
     */
    virtual bool RunOnce(FTimespan WaitTime) = 0;
 
    /*
     * Return the event loops current loop time.
     * 
     * NOT thread safe.
     * 
     * @return the time the event loop last woke up.
     */
    virtual FTimespan GetLoopTime() const = 0;
};
 
/* UE::EventLoop */ }