MemoryReadStream.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "HAL/Platform.h"
#include "HAL/ThreadSafeCounter.h"
#include "Templates/RefCounting.h"
 
/**
 * Represents a block of memory, but abstracts away the underlying layout
 */
class IMemoryReadStream
{
public:
    static TRefCountPtr<IMemoryReadStream> CreateFromCopy(const void* InMemory, int64 InSize);
    static TRefCountPtr<IMemoryReadStream> CreateFromCopy(IMemoryReadStream* InStream);
    static TRefCountPtr<IMemoryReadStream> CreateFromBuffer(void* InMemory, int64 InSize, bool bOwnPointer);
 
    virtual const void* Read(int64& OutSize, int64 InOffset, int64 InSize) = 0;
    virtual int64 GetSize() = 0;
    virtual void CopyTo(void* Buffer, int64 InOffset, int64 InSize);
    virtual void EnsureReadNonBlocking() {};        // Incur any potential wait such that future Read() or CopyTo() calls are wait and thread switch free.
 
    FORCEINLINE uint32 AddRef() const { return uint32(NumRefs.Increment()); }
 
    FORCEINLINE uint32 Release() const
    {
        const int32 Refs = NumRefs.Decrement();
        if (Refs == 0)
        {
            delete this;
        }
        return uint32(Refs);
    }
 
    FORCEINLINE uint32 GetRefCount() const
    {
        return uint32(NumRefs.GetValue());
    }
 
protected:
    virtual ~IMemoryReadStream() {}
 
private:
    mutable FThreadSafeCounter NumRefs;
};
typedef TRefCountPtr<IMemoryReadStream> IMemoryReadStreamRef;