size_of.hpp

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/* This file is part of OpenKalman, a header-only C++ library for
 * Kalman filters and other recursive filters.
 *
 * Copyright (c) 2024-2026 Christopher Lee Ogden <ogden@gatech.edu>
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#ifndef OPENKALMAN_COLLECTIONS_SIZE_OF_HPP
#define OPENKALMAN_COLLECTIONS_SIZE_OF_HPP

#include "values/values.hpp"
#include "collections/functions/get_size.hpp"
#include "collections/concepts/sized.hpp"

namespace OpenKalman::collections
{
#ifdef __cpp_concepts
  template<typename T>
#else
  template<typename T, typename = void>
#endif
  struct size_of {};


#ifdef __cpp_concepts
  template<sized T> requires (not values::fixed<decltype(collections::get_size(std::declval<T>()))>)
  struct size_of<T>
#else
  template<typename T>
  struct size_of<T, std::enable_if_t<
    sized<T> and not values::fixed<decltype(collections::get_size(std::declval<T>()))>>>
#endif
  : std::integral_constant<std::size_t, stdex::dynamic_extent> {};


#ifdef __cpp_concepts
  template<sized T> requires values::fixed<decltype(collections::get_size(std::declval<T>()))>
  struct size_of<T>
#else
  template<typename T>
  struct size_of<T, std::enable_if_t<
    sized<T> and values::fixed<decltype(collections::get_size(std::declval<T>()))>>>
#endif
    : values::fixed_value_of<decltype(collections::get_size(std::declval<T>()))> {};


  template<typename T>
  inline constexpr std::size_t size_of_v = size_of<T>::value;


  template<typename T>
  using size_of_t = std::conditional_t<sized<T>, size_of<T>, values::unbounded_size_t>;

}

#endif