buffer_descriptors.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2020 John Wellbelove
 
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#ifndef ETL_BUFFER_DESCRIPTORS_INCLUDED
#define ETL_BUFFER_DESCRIPTORS_INCLUDED
 
#include "platform.h"
#include "algorithm.h"
#include "array.h"
#include "cyclic_value.h"
#include "delegate.h"
#include "type_traits.h"
 
#include <stddef.h>
 
#if ETL_USING_CPP11
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  template <typename TBuffer, size_t BUFFER_SIZE_, size_t N_BUFFERS_, typename TFlag = bool>
  class buffer_descriptors
  {
  private:
 
    struct descriptor_item;
 
  public:
 
    typedef TBuffer     value_type;
    typedef value_type* pointer;
    typedef size_t      size_type;
    typedef TFlag       flag_type;
 
    static ETL_CONSTANT size_type N_BUFFERS   = N_BUFFERS_;
    static ETL_CONSTANT size_type BUFFER_SIZE = BUFFER_SIZE_;
 
    //*********************************
    //*********************************
    class descriptor
    {
    public:
 
      friend class buffer_descriptors;
 
      static ETL_CONSTANT size_type MAX_SIZE = buffer_descriptors::BUFFER_SIZE;
 
      //*********************************
      descriptor()
        : pdesc_item(ETL_NULLPTR)
      {
      }
 
      //*********************************
      descriptor(const descriptor& other)
        : pdesc_item(other.pdesc_item)
      {
      }
 
      //*********************************
      descriptor& operator=(const descriptor& other)
      {
        pdesc_item = other.pdesc_item;
        return *this;
      }
 
      //*********************************
      pointer data() const
      {
        assert(pdesc_item != ETL_NULLPTR);
  #include "private/diagnostic_null_dereference_push.h"
        return pdesc_item->pbuffer;
  #include "private/diagnostic_pop.h"
      }
 
      //*********************************
      ETL_NODISCARD ETL_CONSTEXPR size_type max_size() const
      {
        return BUFFER_SIZE;
      }
 
      //*********************************
      ETL_NODISCARD
      bool is_allocated() const
      {
        return bool(pdesc_item->in_use);
      }
 
      //*********************************
      ETL_NODISCARD
      bool is_released() const
      {
        return bool(!pdesc_item->in_use);
      }
 
      //*********************************
      ETL_NODISCARD
      bool is_valid() const
      {
        return pdesc_item != ETL_NULLPTR;
      }
 
      //*********************************
      void release()
      {
        pdesc_item->in_use = false;
      }
 
    private:
 
      //*********************************
      descriptor(descriptor_item* pdesc_item_)
        : pdesc_item(pdesc_item_)
      {
      }
 
      //*********************************
      void allocate()
      {
        pdesc_item->in_use = true;
      }

      descriptor_item* pdesc_item;
    };
 
    //*********************************
    //*********************************
    class notification
    {
    public:
 
      //*********************************
      notification()
        : desc()
        , count(0U)
      {
      }
 
      //*********************************
      notification(descriptor desc_, size_t count_)
        : desc(desc_)
        , count(count_)
      {
      }
 
      //*********************************
      ETL_NODISCARD
      descriptor get_descriptor() const
      {
        return desc;
      }
 
      //*********************************
      ETL_NODISCARD
      size_t get_count() const
      {
        return count;
      }
 
    private:
 
      descriptor desc;
      size_t     count;
    };
 
    // The type of the callback function.
    typedef etl::delegate<void(notification)> callback_type;
 
    //*********************************
    buffer_descriptors(TBuffer* pbuffers_, callback_type callback_ = callback_type())
      : callback(callback_)
    {
      for (size_t i = 0UL; i < N_BUFFERS; ++i)
      {
        descriptor_items[i].pbuffer = pbuffers_ + (i * BUFFER_SIZE);
        descriptor_items[i].in_use  = false;
      }
    }
 
    //*********************************
    void set_callback(const callback_type& callback_)
    {
      callback = callback_;
    }
 
    //*********************************
    void clear()
    {
      for (size_t i = 0UL; i < N_BUFFERS; ++i)
      {
        descriptor_items[i].in_use = false;
      }
 
      next.to_first();
    }
 
    //*********************************
    ETL_NODISCARD
    bool is_valid() const
    {
      return callback.is_valid();
    }
 
    //*********************************
    void notify(notification n)
    {
      // Do we have a valid callback?
      if (callback.is_valid())
      {
        callback(n);
      }
    }
 
    //*********************************
    ETL_NODISCARD
    descriptor allocate()
    {
      descriptor desc(&descriptor_items[next]);
 
      if (desc.is_released())
      {
        ++next;
 
        desc.allocate();
 
        return desc;
      }
      else
      {
        return descriptor();
      }
    }
 
    //*********************************
    ETL_NODISCARD
    descriptor allocate(value_type fill_)
    {
      descriptor desc = allocate();
 
      if (desc.is_valid())
      {
        etl::fill_n(desc.data(), BUFFER_SIZE, fill_);
      }
 
      return desc;
    }
 
  private:
 
    //*********************************
    struct descriptor_item
    {
      pointer            pbuffer;
      volatile flag_type in_use;
    };
 
    callback_type                                       callback;
    etl::array<descriptor_item, N_BUFFERS>              descriptor_items;
    etl::cyclic_value<uint_least8_t, 0U, N_BUFFERS - 1> next;
  };
 
  template <typename TBuffer, size_t BUFFER_SIZE_, size_t N_BUFFERS_, typename TFlag>
  ETL_CONSTANT typename buffer_descriptors<TBuffer, BUFFER_SIZE_, N_BUFFERS_, TFlag>::size_type
    buffer_descriptors<TBuffer, BUFFER_SIZE_, N_BUFFERS_, TFlag>::N_BUFFERS;
 
  template <typename TBuffer, size_t BUFFER_SIZE_, size_t N_BUFFERS_, typename TFlag>
  ETL_CONSTANT typename buffer_descriptors<TBuffer, BUFFER_SIZE_, N_BUFFERS_, TFlag>::size_type
    buffer_descriptors<TBuffer, BUFFER_SIZE_, N_BUFFERS_, TFlag>::BUFFER_SIZE;
 
  template <typename TBuffer, size_t BUFFER_SIZE_, size_t N_BUFFERS_, typename TFlag>
  ETL_CONSTANT typename buffer_descriptors<TBuffer, BUFFER_SIZE_, N_BUFFERS_, TFlag>::size_type
    buffer_descriptors<TBuffer, BUFFER_SIZE_, N_BUFFERS_, TFlag>::descriptor::MAX_SIZE;
} // namespace etl
#endif
#endif