IoDispatcherChunkDecoder.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Async/Mutex.h"
#include "IO/IoAllocators.h"
#include "IO/IoContainers.h"
#include "IO/IoChunkEncoding.h"
#include "Tasks/Task.h"
 
namespace UE
{
 
class FIoDispatcherChunkBlockDecoder
    : public IIoChunkBlockDecoder
{
    struct FDecodeContext
    {
        UE::Tasks::FTask    Task;
        FDecodeContext*     Next = nullptr;
    };
 
    struct FQueueEntry
        : public TIntrusiveListElement<FQueueEntry>
    {
        FQueueEntry(FIoChunkBlockDecodeRequest&& InRequest)
            : Request(MoveTemp(InRequest))
        { }
 
        FIoChunkBlockDecodeRequest  Request;
        FQueueEntry*                Next = nullptr;
    };
 
    using FQueueEntryAllocator  = TSingleThreadedSlabAllocator<FQueueEntry, 512>;
    using FQueue                = TIntrusiveList<FQueueEntry>;
 
public:
                                FIoDispatcherChunkBlockDecoder() = default;
    virtual                     ~FIoDispatcherChunkBlockDecoder() = default;
 
    // IIoChunkBlockDecoder
    virtual void                Enqueue(FIoChunkBlockDecodeRequest&& DecodeRequest) override;
 
    void                        Initialize(uint32 MaxWorkerCount, uint32 MaxConsecutiveDecodeJobs, UE::Tasks::ETaskPriority TaskPriority);
    bool                        TryRetractAndExecuteDecodeTasks();
    bool                        TryExecuteDecodeRequest();
    void                        TryDequeueAndLaunchDecodeTasks();
 
private:
    void                        LaunchDecodeTask(FDecodeContext& Ctx, FIoChunkBlockDecodeRequest&& DecodeRequest);
    void                        ProcessDecodeRequest(FIoChunkBlockDecodeRequest&& DecodeRequest, FIoChunkBlockDecodeRequest& OutNext);
 
    
    TArray<FDecodeContext>      DecodeContexts; 
    FDecodeContext*             NextFreeContext = nullptr;
    FQueueEntryAllocator        QueueEntryAllocator;
    FQueue                      QueueEntries;
    uint32                      MaxWorkerCount = 0;
    uint32                      MaxConsecutiveDecodeJobs = 0;
    UE::FMutex                  Mutex;
    UE::Tasks::ETaskPriority    TaskPriority = UE::Tasks::ETaskPriority::BackgroundNormal;
};
 
} // namespace UE