VVMNativeFunction.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#if WITH_VERSE_VM || defined(__INTELLISENSE__)
 
#include "Containers/ArrayView.h"
#include "Containers/StringFwd.h"
#include "VVMFalse.h"
#include "VVMGlobalTrivialEmergentTypePtr.h"
#include "VVMScope.h"
#include "VVMType.h"
#include "VerseVM/VVMNames.h"
 
namespace Verse
{
struct FOpResult;
struct VPackage;
struct VTask;
struct VUniqueString;
 
using FNativeCallResult = FOpResult;
 
// A function that is implemented in C++
struct VNativeFunction : VHeapValue
{
    DECLARE_DERIVED_VCPPCLASSINFO(COREUOBJECT_API, VHeapValue);
    COREUOBJECT_API static TGlobalTrivialEmergentTypePtr<&StaticCppClassInfo> GlobalTrivialEmergentType;
 
    static constexpr char DecoratorString[] = "Native";
 
    // Interface between VerseVM and C++
    using Args = TArrayView<VValue>;
    using FThunkFn = FNativeCallResult (*)(FRunningContext, VValue Self, Args Arguments);
 
    uint32 NumPositionalParameters;
 
    // The C++ function to call
    FThunkFn Thunk;
 
    TWriteBarrier<VUniqueString> Name;
    TWriteBarrier<VValue> Self;
 
    static VNativeFunction& New(FAllocationContext Context, uint32 NumPositionalParameters, FThunkFn Thunk, VUniqueString& InName, VValue InSelf)
    {
        return *new (Context.AllocateFastCell(sizeof(VNativeFunction))) VNativeFunction(Context, NumPositionalParameters, Thunk, &InName, InSelf);
    }
 
    VNativeFunction& Bind(FAllocationContext Context, VValue InSelf)
    {
        checkf(!HasSelf(), TEXT("Attempting to bind `Self` to a `VNativeFunction` that already has it set; this is probably a mistake in the code generation."));
        return VNativeFunction::New(Context, NumPositionalParameters, Thunk, *Name, InSelf);
    }
 
    // Lookup a native function and set it's thunk to a C++ function
    static COREUOBJECT_API void SetThunk(Verse::VPackage* Package, FUtf8StringView VerseScopePath, FUtf8StringView DecoratedName, FThunkFn NativeFuncPtr);
 
    COREUOBJECT_API bool HasSelf() const;
 
    COREUOBJECT_API void AppendToStringImpl(FAllocationContext Context, FUtf8StringBuilderBase& Builder, EValueStringFormat Format, TSet<const void*>& VisitedObjects, uint32 RecursionDepth);
    static void SerializeLayout(FAllocationContext Context, VNativeFunction*& This, FStructuredArchiveVisitor& Visitor);
    void SerializeImpl(FAllocationContext Context, FStructuredArchiveVisitor& Visitor);
 
private:
    VNativeFunction(FAllocationContext Context, uint32 InNumPositionalParameters, FThunkFn InThunk, VUniqueString* InName, VValue InSelf)
        : VHeapValue(Context, &GlobalTrivialEmergentType.Get(Context))
        , NumPositionalParameters(InNumPositionalParameters)
        , Thunk(InThunk)
        , Name(Context, InName)
        , Self(Context, InSelf)
    {
    }
};
 
} // namespace Verse
#endif // WITH_VERSE_VM