itkSingletonMacro.h

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/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkSingletonMacro_h
#define itkSingletonMacro_h
 
#define itkInitGlobalsMacro(VarName)                       \
  {                                                        \
    static auto * staticGlobals = Get##VarName##Pointer(); \
    (void)staticGlobals;                                   \
  }                                                        \
  ITK_MACROEND_NOOP_STATEMENT
 
#define itkGetGlobalDeclarationMacro(Type, VarName) static Type * Get##VarName##Pointer()
 
#define itkGetGlobalSimpleMacro(Class, Type, Name) itkGetGlobalInitializeMacro(Class, Type, Name, Class, (void)0)
 
#define itkGetGlobalValueMacro(Class, Type, Name, Value) \
  itkGetGlobalInitializeMacro(Class, Type, Name, Name, *m_##Name = Value)
 
#define itkGetGlobalInitializeMacro(Class, Type, VarName, SingletonName, Init)                      \
  Type * Class::Get##VarName##Pointer()                                                             \
  {                                                                                                 \
    if (m_##VarName == nullptr)                                                                     \
    {                                                                                               \
      const auto deleteLambda = []() {                                                              \
        delete m_##VarName;                                                                         \
        m_##VarName = nullptr;                                                                      \
      };                                                                                            \
      auto * old_instance = SingletonIndex::GetInstance()->GetGlobalInstance<Type>(#SingletonName); \
      m_##VarName = Singleton<Type>(#SingletonName, deleteLambda);                                  \
      if (old_instance == nullptr)                                                                  \
      {                                                                                             \
        Init;                                                                                       \
      }                                                                                             \
    }                                                                                               \
    return m_##VarName;                                                                             \
  }                                                                                                 \
  ITK_MACROEND_NOOP_STATEMENT
 
#endif