shm/Project4/page.h

#pragma once

#define PTR_TO_LV0(ptr)	(ptr) >> 25
#define PTR_TO_LV1(ptr)	((ptr) >> 15 & 0x3FF)
#define PTR_TO_LV2(ptr)	((ptr) & 0x7FFF)
namespace bg
{
    namespace detail
    {
        struct Span
        {
            bool m_in_use{};
            unsigned char m_size_class{255};
            size_t m_used_count{};
            size_t m_start_page{};
            size_t m_page_count{};

            Span* m_prev{this};
            Span* m_next{this};
            void* m_chunk_list{};

        };

        template<size_t size0, size_t size1, size_t size2>
        struct RadixTree
        {
            struct  NodeV2
            {
                Span* lv2[1 << size2]{0};
            };
            struct NodeV1
            {
                NodeV2* lv1[1 << size1]{0};
            };

            NodeV1* lv0[1 << size0]{0};
        };

        template<typename T>
        struct MetadataAllocator
        {
            void* m_free_list{};
            char* m_free_area{};
            size_t m_free_left{};
        };


        class PageHeap
        {
        public:
            PageHeap();

            void DeallocateSpan(bg::detail::Span* s);

            void RegisterSpan(bg::detail::Span* s);

            bool GrowHeap(size_t page_count);

            bg::detail::Span* AllocateSpan(size_t page_count);

            using  RadixTree = RadixTree<10ul, 10ul, 15ul>;
            RadixTree m_span_map;
            MetadataAllocator<bg::detail::Span> m_span_allocator;
            Span m_free_lists[128]{};
            Span m_large_list{};
        };
    }
}