PageCache.h

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/**
* @file PageCache.cpp.
* @brief The PageCache Class Definitions.
* @author tcmalloc.
*/
 
#pragma once
#include "Core/Core.h"
#include "MemoryPool.h"
#include "Core/Container/SpanList.h"
#include "Core/Container/RadixTrie.h"
#include "ObjectPool.h"
 
namespace Spices {
 
    /**
    * @brief Page memory cache.
    * Third level of memory allocator.
    */
    class PageCache
    {
    public:
 
        /**
        * @brief Constructor Function.
        */
        PageCache() = default;
 
        /**
        * @brief Destructor Function.
        */
        virtual ~PageCache() = default;
 
        /**
        * @brief Copy Constructor Function.
        * @note This Class not allowed copy behaves.
        */
        PageCache(const PageCache&) = delete;
 
        /**
        * @brief Copy Assignment Operation.
        * @note This Class not allowed copy behaves.
        */
        PageCache& operator= (const PageCache&) = delete;
 
        /**
        * @brief Get this single instance.
        * @return Returns this single instance.
        */
        static PageCache* Get() { return &m_PageCache; }
 
        /**
        * @brief Fetch pages span.
        * @param[in] k pages count.
        * @reurn Returns a new span.
        */
        scl::span* NewSpan(size_t k);
 
        /**
        * @brief Find span by memory pointer.
        * @param[in] obj object memory pointer.
        * @return Returns span.
        */
        scl::span* MapObjectToSpan(void* obj) const;
 
        /**
        * @brief Release span from cc to pc,
        * @param[in] s span.
        */
        void ReleaseSpanToPageCache(scl::span* s);
 
    private:
 
        /**
        * @brief Fetch pages span(internal call).
        * @param[in] k pages count.
        * @reurn Returns a new span.
        */
        scl::span* InternalNewSpan(size_t k);
 
    private:
 
        /**
        * @brief this single instance.
        */
        static PageCache m_PageCache;
 
        /**
        * @brief FreeList Array.
        */
        std::array<scl::span_list, MemoryPool::PAGE_NUM> m_SpanLists;
 
        /**
        * @brief ObjectPool for span.
        */
        ObjectPool<scl::span> m_SpanPool;
 
        /**
        * @brief mutex for pc.
        */
        std::mutex m_Mutex;
 
        /**
        * @brief radix trie for [pageId - span]
        */
        scl::radix_trie<64 - MemoryPool::PAGE_SHIFT, 3> m_IdSpanMap;
    };
}