MassEntityHandle.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "MassEntityHandle.generated.h"
 
USTRUCT()
struct alignas(8) FMassEntityHandle
{
    GENERATED_BODY()
 
    FMassEntityHandle() = default;
    FMassEntityHandle(const int32 InIndex, const int32 InSerialNumber)
        : Index(InIndex), SerialNumber(InSerialNumber)
    {
    }
    
    UPROPERTY(VisibleAnywhere, Category = "Mass|Debug", Transient)
    int32 Index = 0;
    
    UPROPERTY(VisibleAnywhere, Category = "Mass|Debug", Transient)
    int32 SerialNumber = 0;
 
    bool operator==(const FMassEntityHandle Other) const
    {
        return Index == Other.Index && SerialNumber == Other.SerialNumber;
    }
 
    bool operator!=(const FMassEntityHandle Other) const
    {
        return !operator==(Other);
    }
 
    bool operator<(const FMassEntityHandle Other) const { return Index < Other.Index; }
 
    bool IsSet() const
    {
        return Index != 0 && SerialNumber != 0;
    }
 
    inline bool IsValid() const
    {
        return IsSet();
    }
 
    void Reset()
    {
        Index = SerialNumber = 0;
    }
 
    uint64 AsNumber() const { return *reinterpret_cast<const uint64*>(this); } // Relying on the fact that this struct only stores 2 integers and is aligned correctly.
    static FMassEntityHandle FromNumber(uint64 Value) 
    { 
        FMassEntityHandle Result;
        *reinterpret_cast<uint64_t*>(&Result) = Value;
        return Result;
    }
 
    friend uint32 GetTypeHash(const FMassEntityHandle Entity)
    {
        return HashCombine(Entity.Index, Entity.SerialNumber);
    }
 
    friend FString LexToString(const FMassEntityHandle Entity)
    {
        return Entity.DebugGetDescription();
    }
 
    FString DebugGetDescription() const
    {
        return FString::Printf(TEXT("i: %d sn: %d"), Index, SerialNumber);
    }
};
 
static_assert(sizeof(FMassEntityHandle) == sizeof(uint64), "Expected FMassEntityHandle to be convertible to a 64-bit integer value, so size needs to be 8 bytes.");
static_assert(alignof(FMassEntityHandle) == sizeof(uint64), "Expected FMassEntityHandle to be convertible to a 64-bit integer value, so alignment needs to be 8 bytes.");