ndn-cxx/tag.hpp

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013-2022 Regents of the University of California.
 *
 * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
 *
 * ndn-cxx 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 3 of the License, or (at your option) any later version.
 *
 * ndn-cxx 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 copies of the GNU General Public License and GNU Lesser
 * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
 */

#ifndef NDN_CXX_TAG_HPP
#define NDN_CXX_TAG_HPP

namespace ndn {

/**
 * @brief Base class for packet tags that can hold any arbitrary information.
 */
class Tag
{
public:
  virtual
  ~Tag() = default;

#ifdef DOXYGEN
  /**
   * @brief Returns an integer that uniquely identifies this Tag type.
   * @sa https://redmine.named-data.net/projects/ndn-cxx/wiki/PacketTagTypes
   */
  static constexpr int
  getTypeId() noexcept
  {
    return <type-identifier>;
  }
#endif // DOXYGEN
};

/**
 * @brief Provides a tag type for simple types.
 * @tparam T the value type
 * @tparam TypeId the TypeId
 */
template<typename T, int TypeId>
class SimpleTag : public Tag
{
public:
  static constexpr int
  getTypeId() noexcept
  {
    return TypeId;
  }

  /**
   * \brief Explicitly convertible from \c T.
   */
  constexpr explicit
  SimpleTag(const T& value) noexcept
    : m_value(value)
  {
  }

  /**
   * \brief Implicitly convertible to \c T.
   * \return A copy of the enclosed value.
   */
  operator T() const
  {
    return m_value;
  }

  /**
   * \brief Returns the enclosed value.
   */
  constexpr const T&
  get() const noexcept
  {
    return m_value;
  }

private:
  T m_value;
};

} // namespace ndn

#endif // NDN_CXX_TAG_HPP