FixedSizeFreeList.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include <Jolt/Core/NonCopyable.h>
#include <Jolt/Core/Mutex.h>
#include <Jolt/Core/Atomics.h>
 
JPH_NAMESPACE_BEGIN
 
template <typename Object>
class FixedSizeFreeList : public NonCopyable
{
private:
    struct ObjectStorage
    {
        Object              mObject;
 
        atomic<uint32>      mNextFreeObject;
    };
 
    static_assert(alignof(ObjectStorage) == alignof(Object), "Object not properly aligned");
 
    const ObjectStorage &   GetStorage(uint32 inObjectIndex) const  { return mPages[inObjectIndex >> mPageShift][inObjectIndex & mObjectMask]; }
    ObjectStorage &         GetStorage(uint32 inObjectIndex)        { return mPages[inObjectIndex >> mPageShift][inObjectIndex & mObjectMask]; }
 
#ifdef JPH_ENABLE_ASSERTS
    atomic<uint32>          mNumFreeObjects;
#endif // JPH_ENABLE_ASSERTS
 
    atomic<uint32>          mAllocationTag;
 
    atomic<uint64>          mFirstFreeObjectAndTag;
 
    uint32                  mPageSize;
 
    uint32                  mPageShift;
 
    uint32                  mObjectMask;
 
    uint32                  mNumPages;
 
    uint32                  mNumObjectsAllocated;
 
    atomic<uint32>          mFirstFreeObjectInNewPage;
 
    ObjectStorage **        mPages = nullptr;
 
    Mutex                   mPageMutex;
 
public:
    static const uint32     cInvalidObjectIndex = 0xffffffff;
 
    static const int        ObjectStorageSize = sizeof(ObjectStorage);
 
    inline                  ~FixedSizeFreeList();
 
    inline void             Init(uint inMaxObjects, uint inPageSize);
 
    template <typename... Parameters>
    inline uint32           ConstructObject(Parameters &&... inParameters);
 
    inline void             DestructObject(uint32 inObjectIndex);
 
    inline void             DestructObject(Object *inObject);
 
    struct Batch
    {
        uint32              mFirstObjectIndex = cInvalidObjectIndex;
        uint32              mLastObjectIndex = cInvalidObjectIndex;
        uint32              mNumObjects = 0;
    };
 
    inline void             AddObjectToBatch(Batch &ioBatch, uint32 inObjectIndex);
 
    inline void             DestructObjectBatch(Batch &ioBatch);
 
    inline Object &         Get(uint32 inObjectIndex)               { return GetStorage(inObjectIndex).mObject; }
 
    inline const Object &   Get(uint32 inObjectIndex) const         { return GetStorage(inObjectIndex).mObject; }
};
 
JPH_NAMESPACE_END
 
#include "FixedSizeFreeList.inl"