Code/Engine/Foundation/Utilities/EnumerableClass.h - dev - redgpu/ezEngine

Code/Engine/Foundation/Utilities/EnumerableClass.h
110 строк4 KB
Ingrater
Clang-format fixes and update to 18.1.1 (#1234)
10 мар 2024, 15:51
10 мар 2024, 15:512f16acf
#pragma once

/// \file

/// \brief Base class to add the ability to another class to enumerate all active instance of it, across DLL boundaries.
///
/// This creates a new class-type that has the static information
/// about all instances that were created from that class. Another class now only has to derive from that class and will
/// then gain the ability to count and enumerate its instances.
///
/// Usage is as follows:
///
/// If you have a class A that you want to be enumerable, add this to its header:
///
///   class EZ_DLL_IMPORT_EXPORT_STUFF A : public ezEnumerable<A>
///   {
///     EZ_DECLARE_ENUMERABLE_CLASS(A); // since A is declared as DLL import/export all code embedded in its body will also work properly
///     ...
///   };
///
/// Also add this somewhere in its source-file:
///
///   EZ_ENUMERABLE_CLASS_IMPLEMENTATION(A);
///
/// That's it, now the class instances can be enumerated with 'GetFirstInstance' and 'GetNextInstance'
template <typename Derived, typename Base = ezNoBase>
class ezEnumerable : public Base
{
public:
  ezEnumerable()
  {
    if (Derived::s_pFirstInstance == nullptr)
      Derived::s_pFirstInstance = this;
    else
      Derived::s_pLastInstance->m_pNextInstance = this;

    Derived::s_pLastInstance = this;
    m_pNextInstance = nullptr;
    ++Derived::s_uiInstances;
  }

  virtual ~ezEnumerable()
  {
    --Derived::s_uiInstances;
    ezEnumerable* pPrev = nullptr;
    ezEnumerable* pCur = Derived::s_pFirstInstance;

    while (pCur)
    {
      if (pCur == this)
      {
        if (pPrev == nullptr)
          Derived::s_pFirstInstance = m_pNextInstance;
        else
          pPrev->m_pNextInstance = m_pNextInstance;

        if (Derived::s_pLastInstance == this)
          Derived::s_pLastInstance = pPrev;

        break;
      }

      pPrev = pCur;
      pCur = pCur->m_pNextInstance;
    }
  }

protected:
  ezEnumerable* m_pNextInstance;
};

/// \brief Insert this macro in a class that is supposed to be enumerable, and pass the class name as the parameter.
///
/// See class ezEnumerable for more details.
#define EZ_DECLARE_ENUMERABLE_CLASS(self) EZ_DECLARE_ENUMERABLE_CLASS_WITH_BASE(self, ezNoBase)

/// \brief Insert this macro in a class that is supposed to be enumerable, and pass the class name as the parameter.
///
/// See class ezEnumerable for more details.
#define EZ_DECLARE_ENUMERABLE_CLASS_WITH_BASE(self, base) \
private:                                                  \
  using ezEnumerableBase = base;                          \
  friend class ezEnumerable<self, base>;                  \
  static ezEnumerable<self, base>* s_pFirstInstance;      \
  static ezEnumerable<self, base>* s_pLastInstance;       \
  static ezUInt32 s_uiInstances;                          \
                                                          \
public:                                                   \
  static self* GetFirstInstance()                         \
  {                                                       \
    return (self*)s_pFirstInstance;                       \
  }                                                       \
  self* GetNextInstance()                                 \
  {                                                       \
    return (self*)m_pNextInstance;                        \
  }                                                       \
  const self* GetNextInstance() const                     \
  {                                                       \
    return (const self*)m_pNextInstance;                  \
  }                                                       \
                                                          \
private:

/// \brief Insert this macro in a cpp file and pass the class name of the to-be-enumerable class as the parameter.
///
/// See class ezEnumerable for more details.
#define EZ_ENUMERABLE_CLASS_IMPLEMENTATION(self)                                \
  ezEnumerable<self, self::ezEnumerableBase>* self::s_pFirstInstance = nullptr; \
  ezEnumerable<self, self::ezEnumerableBase>* self::s_pLastInstance = nullptr;  \
  ezUInt32 self::s_uiInstances = 0