ceph/src/boost/boost/histogram/axis/metadata_base.hpp

   1 // Copyright 2019 Hans Dembinski
   2 //
   3 // Distributed under the Boost Software License, Version 1.0.
   4 // (See accompanying file LICENSE_1_0.txt
   5 // or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 #ifndef BOOST_HISTOGRAM_AXIS_METADATA_BASE_HPP
   8 #define BOOST_HISTOGRAM_AXIS_METADATA_BASE_HPP
   9
  10 #include <boost/core/empty_value.hpp>
  11 #include <boost/histogram/detail/relaxed_equal.hpp>
  12 #include <boost/histogram/detail/replace_type.hpp>
  13 #include <string>
  14 #include <type_traits>
  15
  16 namespace boost {
  17 namespace histogram {
  18 namespace axis {
  19
  20 /// Meta data holder with space optimization for empty meta data types.
  21 template <class Metadata,
  22           class DetailMetadata = detail::replace_default<Metadata, std::string>>
  23 class metadata_base : empty_value<DetailMetadata> {
  24   using base_t = empty_value<DetailMetadata>;
  25
  26 protected:
  27   using metadata_type = DetailMetadata;
  28
  29   // std::string explicitly guarantees nothrow only in C++17
  30   static_assert(std::is_same<metadata_type, std::string>::value ||
  31                     std::is_nothrow_move_constructible<metadata_type>::value,
  32                 "metadata must be nothrow move constructible");
  33
  34   metadata_base() = default;
  35   metadata_base(const metadata_base&) = default;
  36   metadata_base& operator=(const metadata_base&) = default;
  37
  38   // make noexcept because std::string is nothrow move constructible only in C++17
  39   metadata_base(metadata_base&& o) noexcept : base_t(std::move(o)) {}
  40   metadata_base(metadata_type&& o) noexcept : base_t(empty_init_t{}, std::move(o)) {}
  41   // make noexcept because std::string is nothrow move constructible only in C++17
  42   metadata_base& operator=(metadata_base&& o) noexcept {
  43     base_t::operator=(o);
  44     return *this;
  45   }
  46
  47 public:
  48   /// Returns reference to metadata.
  49   metadata_type& metadata() noexcept { return base_t::get(); }
  50
  51   /// Returns reference to const metadata.
  52   const metadata_type& metadata() const noexcept { return base_t::get(); }
  53
  54   bool operator==(const metadata_base& o) const noexcept {
  55     return detail::relaxed_equal(metadata(), o.metadata());
  56   }
  57
  58   bool operator!=(const metadata_base& o) const noexcept {
  59     return operator==(o.metadata());
  60   }
  61 };
  62
  63 } // namespace axis
  64 } // namespace histogram
  65 } // namespace boost
  66
  67 #endif