FreeListAllocator.hpp

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#ifndef DART_COMMON_FREELISTALLOCATOR_HPP_
#define DART_COMMON_FREELISTALLOCATOR_HPP_
 
#include <mutex>
 
#include "dart/common/MemoryAllocator.hpp"
#include "dart/common/MemoryAllocatorDebugger.hpp"
 
namespace dart::common {
 
class FreeListAllocator : public MemoryAllocator
{
public:
  using Debug = MemoryAllocatorDebugger<FreeListAllocator>;
 
  explicit FreeListAllocator(
      MemoryAllocator& baseAllocator = MemoryAllocator::GetDefault(),
      size_t initialAllocation = 1048576 /* 1 MB */);
 
  ~FreeListAllocator() override;
 
  DART_STRING_TYPE(FreeListAllocator);
 
  [[nodiscard]] const MemoryAllocator& getBaseAllocator() const;
 
  [[nodiscard]] MemoryAllocator& getBaseAllocator();
 
  // Documentation inherited
  [[nodiscard]] void* allocate(size_t bytes) noexcept override;
 
  // Documentation inherited
  void deallocate(void* pointer, size_t bytes) override;
 
  // Documentation inherited
  void print(std::ostream& os = std::cout, int indent = 0) const override;
 
private:
  struct MemoryBlockHeader
  {
    size_t mSize;
 
    MemoryBlockHeader* mPrev;
 
    MemoryBlockHeader* mNext;
 
    bool mIsAllocated;
 
    bool mIsNextContiguous;
 
    explicit MemoryBlockHeader(
        size_t size,
        MemoryBlockHeader* prev,
        MemoryBlockHeader* next,
        bool isNextContiguous);
 
    size_t asSizeT() const;
 
    unsigned char* asCharPtr();
 
    const unsigned char* asCharPtr() const;
 
    void split(size_t sizeToSplit);
 
    void merge(MemoryBlockHeader* other);
 
#ifndef NDEBUG
    bool isValid() const;
#endif
  };
 
  bool allocateMemoryBlock(size_t sizeToAllocate);
 
  MemoryAllocator& mBaseAllocator;
 
  mutable std::mutex mMutex;
 
  MemoryBlockHeader* mFirstMemoryBlock{nullptr};
 
  MemoryBlockHeader* mFreeBlock{nullptr};
 
  size_t mTotalAllocatedBlockSize{0};
 
  size_t mTotalAllocatedSize{0};
};
 
} // namespace dart::common
 
#endif // DART_COMMON_FREELISTALLOCATOR_HPP_