xbmc/utils/ComponentContainer.h

   1 /*
   2  *  Copyright (C) 2022 Team Kodi
   3  *  This file is part of Kodi - https://kodi.tv
   4  *
   5  *  SPDX-License-Identifier: GPL-2.0-or-later
   6  *  See LICENSES/README.md for more information.
   7  */
   8
   9 #pragma once
  10
  11 #include "threads/CriticalSection.h"
  12
  13 #include <cstddef>
  14 #include <memory>
  15 #include <mutex>
  16 #include <stdexcept>
  17 #include <typeindex>
  18 #include <unordered_map>
  19 #include <utility>
  20
  21 //! \brief A generic container for components.
  22 //! \details A component has to be derived from the BaseType.
  23 //!          Only a single instance of each derived type can be registered.
  24 //!          Intended use is through inheritance.
  25 template<class BaseType>
  26 class CComponentContainer
  27 {
  28 public:
  29   //! \brief Obtain a component.
  30   template<class T>
  31   std::shared_ptr<T> GetComponent()
  32   {
  33     return std::const_pointer_cast<T>(std::as_const(*this).template GetComponent<T>());
  34   }
  35
  36   //! \brief Obtain a component.
  37   template<class T>
  38   std::shared_ptr<const T> GetComponent() const
  39   {
  40     std::unique_lock<CCriticalSection> lock(m_critSection);
  41     const auto it = m_components.find(std::type_index(typeid(T)));
  42     if (it != m_components.end())
  43       return std::static_pointer_cast<const T>((*it).second);
  44
  45     throw std::logic_error("ComponentContainer: Attempt to obtain non-existent component");
  46   }
  47
  48   //! \brief Returns number of registered components.
  49   std::size_t size() const { return m_components.size(); }
  50
  51 protected:
  52   //! \brief Register a new component instance.
  53   void RegisterComponent(const std::shared_ptr<BaseType>& component)
  54   {
  55     if (!component)
  56       return;
  57
  58     // Note: Extra var needed to avoid clang warning
  59     // "Expression with side effects will be evaluated despite being used as an operand to 'typeid'"
  60     // https://stackoverflow.com/questions/46494928/clang-warning-on-expression-side-effects
  61     const auto& componentRef = *component;
  62
  63     std::unique_lock<CCriticalSection> lock(m_critSection);
  64     m_components.insert({std::type_index(typeid(componentRef)), component});
  65   }
  66
  67   //! \brief Deregister a component.
  68   void DeregisterComponent(const std::type_info& typeInfo)
  69   {
  70     std::unique_lock<CCriticalSection> lock(m_critSection);
  71     m_components.erase(typeInfo);
  72   }
  73
  74 private:
  75   mutable CCriticalSection m_critSection; //!< Critical section for map updates
  76   std::unordered_map<std::type_index, std::shared_ptr<BaseType>>
  77       m_components; //!< Map of components
  78 };