observer.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2014 John Wellbelove
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
copies of the Software, and to permit persons to whom the Software is
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The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
******************************************************************************/
 
#ifndef ETL_OBSERVER_INCLUDED
#define ETL_OBSERVER_INCLUDED
 
//*****************************************************************************
//*****************************************************************************
 
#include "platform.h"
#include "algorithm.h"
#include "vector.h"
#include "exception.h"
#include "error_handler.h"
#include "utility.h"
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  class observer_exception : public exception
  {
  public:
 
    observer_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
      : exception(reason_, file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class observer_list_full : public observer_exception
  {
  public:
 
    observer_list_full(string_type file_name_, numeric_type line_number_)
      : observer_exception(ETL_ERROR_TEXT("observer:full", ETL_OBSERVER_FILE_ID"A"), file_name_, line_number_)
    {
    }
  };
 
  //*********************************************************************
  //*********************************************************************
  template <typename TObserver, const size_t Max_Observers>
  class observable
  {
  private:
 
    //***********************************
    // Item stored in the observer list.
    //***********************************
    struct observer_item
    {
      observer_item(TObserver& observer_)
        : p_observer(&observer_)
        , enabled(true)
      {
      }
 
      TObserver* p_observer;
      bool       enabled;
    };
 
    //***********************************
    // How to compare an observer with an observer list item.
    //***********************************
    struct compare_observers
    {
      compare_observers(TObserver& observer_)
        : p_observer(&observer_)
      {
      }
 
      bool operator ()(const observer_item& item) const
      {
        return p_observer == item.p_observer;
      }
 
      TObserver* p_observer;
    };
 
  public:
 
    typedef size_t size_type;
 
    typedef etl::vector<observer_item, Max_Observers> Observer_List;
 
    //*****************************************************************
    //*****************************************************************
    void add_observer(TObserver& observer)
    {
      // See if we already have it in our list.
      typename Observer_List::iterator i_observer_item = find_observer(observer);
 
      // Not there?
      if (i_observer_item == observer_list.end())
      {
        // Is there enough room?
        ETL_ASSERT_OR_RETURN(!observer_list.full(), ETL_ERROR(etl::observer_list_full));
 
        // Add it.
        observer_list.push_back(observer_item(observer));
      }
    }
 
    //*****************************************************************
    //*****************************************************************
    bool remove_observer(TObserver& observer)
    {
      // See if we have it in our list.
      typename Observer_List::iterator i_observer_item = find_observer(observer);
 
      // Found it?
      if (i_observer_item != observer_list.end())
      {
        // Erase it.
        observer_list.erase(i_observer_item);
        return true;
      }
      else
      {
        return false;
      }
    }
 
    //*****************************************************************
    //*****************************************************************
    void enable_observer(TObserver& observer, bool state = true)
    {
      // See if we have it in our list.
      typename Observer_List::iterator i_observer_item = find_observer(observer);
 
      // Found it?
      if (i_observer_item != observer_list.end())
      {
        i_observer_item->enabled = state;
      }
    }
 
    //*****************************************************************
    //*****************************************************************
    void disable_observer(TObserver& observer)
    {
      // See if we have it in our list.
      typename Observer_List::iterator i_observer_item = find_observer(observer);
 
      // Found it?
      if (i_observer_item != observer_list.end())
      {
        i_observer_item->enabled = false;
      }
    }
 
    //*****************************************************************
    //*****************************************************************
    void clear_observers()
    {
      observer_list.clear();
    }
 
    //*****************************************************************
    //*****************************************************************
    size_type number_of_observers() const
    {
      return observer_list.size();
    }
 
    //*****************************************************************
    //*****************************************************************
    template <typename TNotification>
    void notify_observers(TNotification n)
    {
      typename Observer_List::iterator i_observer_item = observer_list.begin();
 
      while (i_observer_item != observer_list.end())
      {
        if (i_observer_item->enabled)
        {
          i_observer_item->p_observer->notification(n);
        }
 
        ++i_observer_item;
      }
    }
 
    //*****************************************************************
    //*****************************************************************
    void notify_observers()
    {
      typename Observer_List::iterator i_observer_item = observer_list.begin();
 
      while (i_observer_item != observer_list.end())
      {
        if (i_observer_item->enabled)
        {
          i_observer_item->p_observer->notification();
        }
 
        ++i_observer_item;
      }
    }
 
  protected:
 
    ~observable()
    {
    }
 
  private:
 
    //*****************************************************************
    //*****************************************************************
    typename Observer_List::iterator find_observer(TObserver& observer_)
    {
      return etl::find_if(observer_list.begin(), observer_list.end(), compare_observers(observer_));
    }

    Observer_List observer_list;
  };
 
#if ETL_USING_CPP11 && !defined(ETL_OBSERVER_FORCE_CPP03_IMPLEMENTATION)
  template <typename... TTypes>
  class observer;
 
  //*****************************************************************
  //*****************************************************************
  template <typename T1, typename... TRest>
  class observer<T1, TRest...> : public observer<T1>, public observer<TRest...>
  {
  public:
 
    ETL_STATIC_ASSERT((!etl::has_duplicates<T1, TRest...>::value), "Observer has duplicate notification types");
 
    using observer<T1>::notification;
    using observer<TRest...>::notification;
  };
 
  //*****************************************************************
  //*****************************************************************
  template <typename T1>
  class observer<T1>
  {
  public:
 
    virtual ~observer() = default;
 
    virtual void notification(T1) = 0;
  };
 
  //*****************************************************************
  //*****************************************************************
  template <>
  class observer<void>
  {
  public:
 
    virtual ~observer() = default;
 
    virtual void notification() = 0;
  };
 
#else
 
  //*********************************************************************
  //*********************************************************************
  template <typename T1,
            typename T2  = void,
            typename T3  = void,
            typename T4  = void,
            typename T5  = void,
            typename T6  = void,
            typename T7  = void,
            typename T8  = void>
  class observer : public observer<T1>
                 , public observer<T2>
                 , public observer<T3>
                 , public observer<T4>
                 , public observer<T5>
                 , public observer<T6>
                 , public observer<T7>
                 , public observer<T8>
  {
  public:
    virtual ~observer() {}
 
    using observer<T1>::notification;
    using observer<T2>::notification;
    using observer<T3>::notification;
    using observer<T4>::notification;
    using observer<T5>::notification;
    using observer<T6>::notification;
    using observer<T7>::notification;
    using observer<T8>::notification;
  };
 
  //*********************************************************************
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3,
            typename T4,
            typename T5,
            typename T6,
            typename T7>
  class observer<T1, T2, T3, T4, T5, T6, T7> : public observer<T1>
                                             , public observer<T2>
                                             , public observer<T3>
                                             , public observer<T4>
                                             , public observer<T5>
                                             , public observer<T6>
                                             , public observer<T7>
  {
  public:
 
    virtual ~observer() {}
    using observer<T1>::notification;
    using observer<T2>::notification;
    using observer<T3>::notification;
    using observer<T4>::notification;
    using observer<T5>::notification;
    using observer<T6>::notification;
    using observer<T7>::notification;
  };
 
  //*********************************************************************
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3,
            typename T4,
            typename T5,
            typename T6>
  class observer<T1, T2, T3, T4, T5, T6> : public observer<T1>
                                         , public observer<T2>
                                         , public observer<T3>
                                         , public observer<T4>
                                         , public observer<T5>
                                         , public observer<T6>
  {
  public:
 
    virtual ~observer() {}
    using observer<T1>::notification;
    using observer<T2>::notification;
    using observer<T3>::notification;
    using observer<T4>::notification;
    using observer<T5>::notification;
    using observer<T6>::notification;
  };
 
  //*********************************************************************
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3,
            typename T4,
            typename T5>
  class observer<T1, T2, T3, T4, T5> : public observer<T1>
                                     , public observer<T2>
                                     , public observer<T3>
                                     , public observer<T4>
                                     , public observer<T5>
  {
  public:
 
    virtual ~observer() {}
    using observer<T1>::notification;
    using observer<T2>::notification;
    using observer<T3>::notification;
    using observer<T4>::notification;
    using observer<T5>::notification;
  };
 
  //*********************************************************************
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3,
            typename T4>
  class observer<T1, T2, T3, T4> : public observer<T1>
                                 , public observer<T2>
                                 , public observer<T3>
                                 , public observer<T4>
  {
  public:
 
    virtual ~observer() {}
    using observer<T1>::notification;
    using observer<T2>::notification;
    using observer<T3>::notification;
    using observer<T4>::notification;
  };
 
  //*********************************************************************
  //*********************************************************************
  template <typename T1,
            typename T2,
            typename T3>
  class observer<T1, T2, T3> : public observer<T1>
                             , public observer<T2>
                             , public observer<T3>
  {
  public:
 
    virtual ~observer() {}
    using observer<T1>::notification;
    using observer<T2>::notification;
    using observer<T3>::notification;
  };
 
  //*********************************************************************
  //*********************************************************************
  template <typename T1,
            typename T2>
  class observer<T1, T2> : public observer<T1>
                         , public observer<T2>
  {
  public:
 
    virtual ~observer() {}
    using observer<T1>::notification;
    using observer<T2>::notification;
  };
 
  //*********************************************************************
  //*********************************************************************
  template <typename T1>
  class observer<T1>
  {
  public:
 
    virtual ~observer() {}
    virtual void notification(T1) = 0;
  };
 
  //*********************************************************************
  //*********************************************************************
  template <>
  class observer<void>
  {
  public:
 
    virtual ~observer() {}
    virtual void notification() = 0;
  };
 
#endif
}
 
#endif