wrapped_petsc.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2023 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner

// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

#ifndef LIBMESH_WRAPPED_PETSC_H
#define LIBMESH_WRAPPED_PETSC_H

#include "libmesh/libmesh_config.h"

#ifdef LIBMESH_HAVE_PETSC

// C++ includes
#include <utility> // std::swap, std::move

namespace libMesh
{

// 该模板类包装了PETSc对象，并专门将析构函数定制为调用相应的 "XXXDestroy()" 程序。
template <typename T>
struct WrappedPetsc
{
  WrappedPetsc() : obj() {}

  WrappedPetsc(T obj_in) : obj(obj_in) {}

  ~WrappedPetsc()
  {
    destroy();
  }

  void reset_to_zero()
  {
    destroy();
    obj = nullptr;
  }

  WrappedPetsc(const WrappedPetsc & other) = delete;
  WrappedPetsc & operator= (const WrappedPetsc &) = delete;

  WrappedPetsc(WrappedPetsc && other) noexcept
    : obj(other.obj)
  {
    other.obj = nullptr;
  }

  WrappedPetsc & operator= (WrappedPetsc && other) noexcept
  {
    WrappedPetsc tmp(std::move(other));
    std::swap(tmp, *this);
    return *this;
  }

  T * get() { return &obj; }

  operator T() const { return obj; }

  T & operator*() { return obj; }

  operator bool() const { return obj != nullptr; }

  void destroy();
private:
  T obj;
};

} // namespace libMesh

#endif // LIBMESH_HAVE_PETSC

#endif