empty.hpp

// This file is part of the ACTS project.
//
// Copyright (C) 2016 CERN for the benefit of the ACTS project
//
// 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/.
 
#pragma once
 
// Project include(s)
#include "detray/definitions/detail/qualifiers.hpp"
#include "detray/utils/ranges/ranges.hpp"
 
namespace detray::ranges {

template <typename value_t>
class empty_view : public detray::ranges::view_interface<empty_view<value_t>> {
 public:
  using iterator_t = value_t*;

  DETRAY_HOST_DEVICE
  static constexpr value_t* begin() noexcept { return nullptr; }

  DETRAY_HOST_DEVICE
  static constexpr value_t* end() noexcept { return nullptr; }

  DETRAY_HOST_DEVICE
  static constexpr value_t* data() noexcept { return nullptr; }

  DETRAY_HOST_DEVICE
  static constexpr std::size_t size() noexcept { return 0; }

  DETRAY_HOST_DEVICE
  static constexpr bool empty() noexcept { return true; }

  DETRAY_HOST_DEVICE
  constexpr value_t front() const noexcept = delete;
 
  DETRAY_HOST_DEVICE
  constexpr value_t back() const noexcept = delete;
 
  DETRAY_HOST_DEVICE
  constexpr value_t operator[](const dindex) const noexcept = delete;
};
 
namespace views {
 
template <typename value_t>
using empty = empty_view<value_t>;
 
}  // namespace views
 
template <class T>
inline constexpr bool enable_borrowed_range<detray::ranges::empty_view<T>> =
    true;
 
}  // namespace detray::ranges