delegate_observable.h

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/******************************************************************************
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Embedded Template Library.
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Copyright(c) 2023 John Wellbelove
 
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#ifndef ETL_DELEGATE_OBSERVABLE_INCLUDED
#define ETL_DELEGATE_OBSERVABLE_INCLUDED
 
#include "platform.h"
#include "delegate.h"
#include "array.h"
 
namespace etl
{
  //*********************************************************************
  //*********************************************************************
  template <typename TNotification, size_t Max_Observers>
  class delegate_observable
  {
  public:
    
    typedef etl::delegate<void(TNotification)> delegate_type;
 
  private:
 
    typedef etl::array<delegate_type, Max_Observers> DelegateList;
 
  public:
 
    typedef size_t        size_type;
    
    typedef TNotification notification_type;
 
    //*****************************************************************
    //*****************************************************************
    ETL_CONSTEXPR14 delegate_observable()
      : delegate_list()
      , delegate_count(0)
    {
    }
 
#if ETL_USING_CPP11
    //*****************************************************************
    //*****************************************************************
    template <typename... TDelegate>
    ETL_CONSTEXPR14 delegate_observable(TDelegate&&... delegates)
      : delegate_list{ etl::forward<TDelegate>(delegates)... }
      , delegate_count(sizeof...(delegates))
    {
      ETL_STATIC_ASSERT(Max_Observers >= sizeof...(delegates), "Number of delegates exceeds maximum observers");
      ETL_STATIC_ASSERT((etl::are_all_same<delegate_type, etl::decay_t<TDelegate>...>::value), "All delegates must be delegate_type");
    }
 
    //*****************************************************************
    //*****************************************************************
    template <typename... TDelegate>
    ETL_CONSTEXPR14 delegate_observable(notification_type, TDelegate&&... delegates)
      : delegate_observable(etl::forward<TDelegate>(delegates)...)
    {
    }
#endif
 
    //*****************************************************************
    //*****************************************************************
    ETL_CONSTEXPR14 bool add_observer(delegate_type observer)
    {
      for (size_t i = 0; i < Max_Observers; ++i)
      {
        if (delegate_list[i] == observer)
        {
          // Already there, so just return.
          return true;
        }
      }
 
      // If we get here, then we need to add it.
      for (size_t i = 0; i < Max_Observers; ++i)
      {
        if (!delegate_list[i].is_valid())
        {
          // Found an empty slot, so add it.
          delegate_list[i] = observer;
          ++delegate_count;
          return true;
        }
      }
 
      return false;
    }
 
    //*****************************************************************
    //*****************************************************************
    ETL_CONSTEXPR14 bool remove_observer(const delegate_type& observer)
    {
      for (size_t i = 0; i < Max_Observers; ++i)
      {
        if (delegate_list[i] == observer)
        {
          // Clear it.
          delegate_list[i].clear();
          --delegate_count;
          return true;
        }
      }
       
      return false;
    }
 
    //*****************************************************************
    //*****************************************************************
    ETL_CONSTEXPR14 void clear_observers()
    {
      for (size_t i = 0; i < Max_Observers; ++i)
      {
        delegate_list[i].clear();
      }
 
      delegate_count = 0;
    }
 
    //*****************************************************************
    //*****************************************************************
    ETL_CONSTEXPR14 size_type number_of_observers() const
    {
      return delegate_count;
    }
 
    //*****************************************************************
    //*****************************************************************
    ETL_CONSTEXPR14 void notify_observers(notification_type n) const
    {
      if (delegate_count != 0)
      {
        for (size_t i = 0; i < Max_Observers; ++i)
        {
          delegate_list[i].call_if(n);
        }
      }
    }
 
  private:
 
    DelegateList delegate_list;
    
    size_t delegate_count;
  };
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_CPP17
  template <typename TNotification, typename... TDelegates>
  delegate_observable(TNotification, TDelegates...) -> delegate_observable<TNotification, sizeof...(TDelegates)>;
#endif
}
 
#endif