94 lines
4.2 KiB
C
94 lines
4.2 KiB
C
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// Copyright Epic Games, Inc. All Rights Reserved.
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#pragma once
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#include "pma/Defs.h"
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#include "pma/MemoryResource.h"
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#include "pma/ScopedPtr.h"
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#include <cstddef>
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namespace pma {
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/**
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@brief Serves allocations from a preallocated memory region.
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@see MemoryResource
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*/
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class ArenaMemoryResource : public MemoryResource {
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public:
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/**
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@brief Constructor
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@param initialSize
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The size of the first allocated region from which allocation requests are served.
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@param regionSize
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When a memory region backing allocation requests has not enough free space to serve an
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allocation, an additional region is allocated for both the current and all subsequent allocations.
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This parameter denotes the size of these additionally allocated regions.
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@param growthFactor
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It describes by which factor should each subsequently allocated region be scaled,
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relative to the previous region. A list of possible region allocation would look like:
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regions = {initialSize, regionSize, regions[1] * growthFactor, regions[2] * growthFactor, ... , regions[n - 1] * growthFactor}
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@param upstream
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The backing memory region will be allocated using the given upstream MemoryResource.
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*/
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PMAAPI ArenaMemoryResource(std::size_t initialSize, std::size_t regionSize, float growthFactor, MemoryResource* upstream);
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/**
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@brief Constructor
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@param regionSize
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When a memory region backing allocation requests has not enough free space to serve an
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allocation, an additional region is allocated for both the current and all subsequent allocations.
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This parameter denotes the size of the initial and all subsequently allocated regions.
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@param growthFactor
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It describes by which factor should each subsequently allocated region be scaled,
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relative to the previous region. A list of possible region allocation would look like:
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regions = {initialSize, regionSize, regions[1] * growthFactor, regions[2] * growthFactor, ... , regions[n - 1] * growthFactor}
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@param upstream
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The backing memory region will be allocated using the given upstream MemoryResource.
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*/
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PMAAPI ArenaMemoryResource(std::size_t regionSize, float growthFactor, MemoryResource* upstream);
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/**
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@brief Constructor
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@param regionSize
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When a memory region backing allocation requests has not enough free space to serve an
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allocation, an additional region is allocated for both the current and all subsequent allocations.
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This parameter denotes the size of the initial and all subsequently allocated regions.
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@note
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The growth factor in this case will be 1.0, i.e. no growth.
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@param upstream
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The backing memory region will be allocated using the given upstream MemoryResource.
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*/
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PMAAPI ArenaMemoryResource(std::size_t regionSize, MemoryResource* upstream);
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PMAAPI ~ArenaMemoryResource();
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ArenaMemoryResource(const ArenaMemoryResource&) = delete;
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ArenaMemoryResource& operator=(const ArenaMemoryResource&) = delete;
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PMAAPI ArenaMemoryResource(ArenaMemoryResource&&);
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PMAAPI ArenaMemoryResource& operator=(ArenaMemoryResource&&);
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/**
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@brief All allocations will be served from the currently active memory region.
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*/
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PMAAPI void* allocate(std::size_t size, std::size_t alignment) override;
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/**
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@brief This is a no-op, and the regions are only freed when the arena itself is destroyed.
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*/
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PMAAPI void deallocate(void* ptr, std::size_t size, std::size_t alignment) override;
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/**
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@brief The upstream memory resource was passed through the constructor and is backing all arena allocations.
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*/
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PMAAPI MemoryResource* getUpstreamMemoryResource() const;
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private:
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class Impl;
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ScopedPtr<Impl, FactoryDestroy<Impl> > pImpl;
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};
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} // namespace pma
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