text: #pragma once
  
  #include <AK/HashMap.h>
  #include <AK/RefPtr.h>
  #include <AK/RefCounted.h>
  #include <Kernel/VM/PhysicalPage.h>
  #include <Kernel/VM/RangeAllocator.h>
  
  class PageDirectory : public RefCounted<PageDirectory> {
      friend class MemoryManager;
  
  public:
      static NonnullRefPtr<PageDirectory> create_for_userspace(const RangeAllocator* parent_range_allocator = nullptr) { return adopt(*new PageDirectory(parent_range_allocator)); }
      static NonnullRefPtr<PageDirectory> create_at_fixed_address(PhysicalAddress paddr) { return adopt(*new PageDirectory(paddr)); }
      ~PageDirectory();
  
      dword cr3() const { return m_directory_page->paddr().get(); }
      PageDirectoryEntry* entries() { return reinterpret_cast<PageDirectoryEntry*>(cr3()); }
  
      void flush(VirtualAddress);
  
      RangeAllocator& range_allocator() { return m_range_allocator; }
  
  private:
      explicit PageDirectory(const RangeAllocator* parent_range_allocator);
      explicit PageDirectory(PhysicalAddress);
  
      RangeAllocator m_range_allocator;
      RefPtr<PhysicalPage> m_directory_page;
      HashMap<unsigned, RefPtr<PhysicalPage>> m_physical_pages;
  };
  