LinearAllocator.h

Go to the documentation of this file.

// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "HAL/Platform.h"
#include "HAL/UnrealMemory.h"
#include "HAL/CriticalSection.h"
 
#ifndef UE_ENABLE_LINEAR_VIRTUAL_ALLOCATOR
#   define UE_ENABLE_LINEAR_VIRTUAL_ALLOCATOR PLATFORM_HAS_FPlatformVirtualMemoryBlock
#endif
 
 
#if UE_ENABLE_LINEAR_VIRTUAL_ALLOCATOR
 
struct FLinearAllocator
{
    CORE_API FLinearAllocator(SIZE_T ReserveMemorySize);
    UE_FORCEINLINE_HINT ~FLinearAllocator()
    {
        VirtualMemory.FreeVirtual();
    }
 
    CORE_API void* Allocate(SIZE_T Size, uint32 Alignment = 8);
 
    UE_FORCEINLINE_HINT SIZE_T GetAllocatedMemorySize() const
    {
        return Committed;
    }
 
protected:
    FCriticalSection Lock;
    FPlatformMemory::FPlatformVirtualMemoryBlock VirtualMemory;
    SIZE_T Reserved;
    SIZE_T Committed = 0;
    SIZE_T CurrentOffset = 0;
 
    bool CanFit(SIZE_T Size, uint32 Alignment) const;
    bool ContainsPointer(const void* Ptr) const;
};
 
#else
 
struct FLinearBlockAllocator
{
    CORE_API FLinearBlockAllocator(SIZE_T);
    CORE_API ~FLinearBlockAllocator();
 
    CORE_API void* Allocate(SIZE_T Size, uint32 Alignment = 8);
 
    UE_FORCEINLINE_HINT SIZE_T GetAllocatedMemorySize() const
    {
        return TotalAllocated;
    }
 
private:
    struct FBlock
    {
        FBlock* Next;
        SIZE_T BlockSize;
    };
 
    FCriticalSection Lock;
    FBlock* FirstHeader = nullptr;
    FBlock* CurrentHeader = nullptr;
    uint8* CurrentBlock = nullptr;
    SIZE_T CurrentOffset = 0;
    SIZE_T CurrentBlockSize = 0;
    SIZE_T TotalAllocated = 0;
 
    void AllocateNewBlock(SIZE_T Size);
    bool CanFit(SIZE_T Size, uint32 Alignment) const;
};
 
typedef FLinearBlockAllocator FLinearAllocator;
 
#endif  //~UE_ENABLE_LINEAR_VIRTUAL_ALLOCATOR
 
CORE_API FLinearAllocator& GetPersistentLinearAllocator();
 
struct FPersistentLinearAllocatorExtends
{
    uint64 Address = 0;
    uint64 Size = 0;
};
 
// Special case for the FPermanentObjectPoolExtents to reduce the amount of pointer dereferencing
extern CORE_API FPersistentLinearAllocatorExtends GPersistentLinearAllocatorExtends;