etl/include/etl/imemory_block_allocator.h

///\file

/******************************************************************************
The MIT License(MIT)

Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com

Copyright(c) 2021 John Wellbelove

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******************************************************************************/

#ifndef ETL_MEMORY_BLOCK_ALLOCATOR_INCLUDED
#define ETL_MEMORY_BLOCK_ALLOCATOR_INCLUDED

#include "platform.h"
#include "nullptr.h"
#include "successor.h"

namespace etl
{
  //*****************************************************************************
  /// The interface for a memory block pool.
  //*****************************************************************************
  class imemory_block_allocator : public successor<imemory_block_allocator>
  {
  public:

    //*****************************************************************************
    /// Default constructor.
    //*****************************************************************************
    imemory_block_allocator() {}

    //*****************************************************************************
    /// Try to allocate a memory block of the required size.
    /// If this allocator cannot, then pass the request on the the successor, if
    /// configured.
    //*****************************************************************************
    void* allocate(size_t required_size, size_t required_alignment)
    {
      // Call the derived implementation.
      void* p = allocate_block(required_size, required_alignment);

      // If that failed...
      if (p == ETL_NULLPTR)
      {
        /// ...and we have a successor...
        if (has_successor())
        {
          // ...try to allocate from the next one in the chain.
          return get_successor().allocate(required_size, required_alignment);
        }
      }

      return p;
    }

    //*****************************************************************************
    /// Try to release a memory block of the required size.
    /// If this allocator cannot, then pass the request on the the successor, if
    /// configured.
    //*****************************************************************************
    bool release(const void* const p)
    {
      bool was_released = release_block(p);

      // If that failed...
      if (!was_released)
      {
        /// ...and we have a successor...
        if (has_successor())
        {
          // ...try to release from the next one in the chain.
          was_released = get_successor().release(p);
        }
      }

      return was_released;
    }

    //*****************************************************************************
    /// Check if the memory block is owned by this allocator.
    /// If this allocator does not own it, then pass the request on the the
    /// successor, if configured.
    //*****************************************************************************
    bool is_owner_of(const void* const p) const
    {
      bool is_owner = is_owner_of_block(p);

      // If that failed...
      if (!is_owner)
      {
        /// ...and we have a successor...
        if (has_successor())
        {
          // ...check with the next one in the chain.
          is_owner = get_successor().is_owner_of(p);
        }
      }

      return is_owner;
    }

  protected:

    virtual void* allocate_block(size_t required_size, size_t required_alignment) = 0;
    virtual bool  release_block(const void* const)                                = 0;
    virtual bool  is_owner_of_block(const void* const) const                      = 0;

  private:

    // No copying allowed.
    imemory_block_allocator(const etl::imemory_block_allocator&) ETL_DELETE;
    imemory_block_allocator& operator=(const imemory_block_allocator&) ETL_DELETE;
  };
} // namespace etl

#endif