VVMLocalAllocator.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#if WITH_VERSE_VM || defined(__INTELLISENSE__)
 
#include "HAL/Platform.h" // IWYU pragma: keep
#include "verse_local_allocator_ue.h"
#include <cstddef>
 
namespace Verse
{
class FSubspace;
 
// This is really pas_local_allocator.
struct alignas(PAS_LOCAL_ALLOCATOR_ALIGNMENT) FLocalAllocator final
{
    FLocalAllocator() = default;
    COREUOBJECT_API ~FLocalAllocator();
 
    void Initialize(FSubspace* Subspace, size_t Size)
    {
        verse_local_allocator_construct(reinterpret_cast<pas_local_allocator*>(this), reinterpret_cast<pas_heap*>(Subspace), Size, sizeof(FLocalAllocator));
    }
 
    void Stop()
    {
        verse_local_allocator_stop(reinterpret_cast<pas_local_allocator*>(this));
    }
 
    std::byte* Allocate()
    {
        return static_cast<std::byte*>(verse_local_allocator_allocate(reinterpret_cast<pas_local_allocator*>(this)));
    }
 
    std::byte* TryAllocate()
    {
        return static_cast<std::byte*>(verse_local_allocator_try_allocate(reinterpret_cast<pas_local_allocator*>(this)));
    }
 
private:
    // It so happens to be the case that we only create FLocalAllocators on the UE side when it's for sizes that qualify for the small segregated page config variant.
    // That variant may require a smaller local allocator size, because it has fewer bits, depending on system page size.
    //
    // If we ever started getting panics inside verse_local_allocator_construct() because our size was two small, we should change this to use
    // VERSE_MAX_SEGREGATED_LOCAL_ALLOCATOR_SIZE instead.
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wgnu-folding-constant"
#pragma clang diagnostic ignored "-Wvla-cxx-extension"
#endif // defined(__clang__)
    char OpaqueData[VERSE_SMALL_SEGREGATED_LOCAL_ALLOCATOR_SIZE];
#if defined(__clang__)
#pragma clang diagnostic pop
#endif // defined(__clang__)
};
 
} // namespace Verse
#endif // WITH_VERSE_VM