RegisterCompiledInObjects.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "UObject/ObjectMacros.h"
 
#if UE_WITH_CONSTINIT_UOBJECT 
 
#include "Containers/ArrayView.h"
#include "Misc/TVariant.h"
#include "UObject/UObjectGlobals.h"
 
class UClass;
class UDelegateFunction;
class UObject;
class UPackage;
 
// Register partially initialized objects such as packages, classes, structs and enums for runtime construction
// This structure is stored as a linked list where possible to avoid dynamic allocation during startup 
struct FRegisterCompiledInObjects
{
    using FIntrinsicClassConstructor = void();
 
    // Register an intrinsic class with a special initialization function
    FRegisterCompiledInObjects(UClass* InClass, FIntrinsicClassConstructor* InConstructor)
        : FRegisterCompiledInObjects(FIntrinsicClassRegistrant{InClass, InConstructor})
    {
    }
 
    // Register a package and some objects that might otherwise not be registered - e.g. noexport structs and delegate
    // function signatures. ArrayView should point to static memory
    FRegisterCompiledInObjects(UPackage* InPackage, TConstArrayView<UObject*> Others)
        : FRegisterCompiledInObjects(FPackageRegistrants{InPackage, Others})
    {
    }
 
    // Primary entry point - register a batch of objects from a single generated cpp file all together
    // ArrayView should point to static memory
    // Constructors for each possible set of parameters are provided to reduce code size at the call site
    FRegisterCompiledInObjects(
        TConstArrayView<UClass*> InClasses,
        TConstArrayView<UScriptStruct*> InStructs,
        TConstArrayView<UEnum*> InEnums)
        : FRegisterCompiledInObjects(FClassRegistrants{InClasses, InStructs, InEnums})
    {
    }
    FRegisterCompiledInObjects(
        TConstArrayView<UClass*> InClasses)
        : FRegisterCompiledInObjects(FClassRegistrants{InClasses, {}, {}})
    {
    }
    FRegisterCompiledInObjects(
        TConstArrayView<UClass*> InClasses,
        TConstArrayView<UScriptStruct*> InStructs)
        : FRegisterCompiledInObjects(FClassRegistrants{InClasses, InStructs, {}})
    {
    }
    FRegisterCompiledInObjects(
        TConstArrayView<UClass*> InClasses,
        TConstArrayView<UEnum*> InEnums)
        : FRegisterCompiledInObjects(FClassRegistrants{InClasses, {}, InEnums})
    {
    }
    FRegisterCompiledInObjects(
        TConstArrayView<UScriptStruct*> InStructs,
        TConstArrayView<UEnum*> InEnums)
        : FRegisterCompiledInObjects(FClassRegistrants{{}, InStructs, InEnums})
    {
    }
    FRegisterCompiledInObjects(
        TConstArrayView<UScriptStruct*> InStructs)
        : FRegisterCompiledInObjects(FClassRegistrants{{}, InStructs, {}})
    {
    }
    FRegisterCompiledInObjects(
        TConstArrayView<UEnum*> InEnums)
        : FRegisterCompiledInObjects(FClassRegistrants{{}, {}, InEnums})
    {
    }
 
    struct FPackageRegistrants
    {
        UPackage* Package = nullptr;
        TConstArrayView<UObject*> Objects;
    };
 
    struct FClassRegistrants
    {
        TConstArrayView<UClass*> Classes;
        TConstArrayView<UScriptStruct*> Structs;
        TConstArrayView<UEnum*> Enums;
    };
 
    struct FIntrinsicClassRegistrant
    {
        UClass* IntrinsicClass = nullptr;
        FIntrinsicClassConstructor* Constructor = nullptr;
    };
 
    TVariant<FPackageRegistrants, FClassRegistrants, FIntrinsicClassRegistrant> Registrants;
    FRegisterCompiledInObjects* ListNext = nullptr;
    
    // Delegating constructor
    template<typename VARIANT>
    FRegisterCompiledInObjects(VARIANT&& Variant)
    : Registrants(TInPlaceType<VARIANT>{}, Forward<VARIANT>(Variant))
    {
        Register();
    }
 
    // Register all our objects for deferred construction
    COREUOBJECT_API void Register();
};
 
#endif