ceph/src/common/backport14.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15 #include <memory>
  16 #include <type_traits>
  17
  18 #ifndef CEPH_COMMON_BACKPORT14_H
  19 #define CEPH_COMMON_BACKPORT14_H
  20
  21 // Library code from C++14 that can be implemented in C++11.
  22
  23 namespace ceph {
  24 template<typename T>
  25 using remove_extent_t = typename std::remove_extent<T>::type;
  26 template<typename T>
  27 using remove_reference_t = typename std::remove_reference<T>::type;
  28 template<typename T>
  29 using result_of_t = typename std::result_of<T>::type;
  30
  31 namespace _backport14 {
  32 template<typename T>
  33 struct uniquity {
  34   using datum = std::unique_ptr<T>;
  35 };
  36
  37 template<typename T>
  38 struct uniquity<T[]> {
  39   using array = std::unique_ptr<T[]>;
  40 };
  41
  42 template<typename T, std::size_t N>
  43 struct uniquity<T[N]> {
  44   using verboten = void;
  45 };
  46
  47 template<typename T, typename... Args>
  48 inline typename uniquity<T>::datum make_unique(Args&&... args) {
  49   return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
  50 }
  51
  52 template<typename T>
  53 inline typename uniquity<T>::array make_unique(std::size_t n) {
  54   return std::unique_ptr<T>(new remove_extent_t<T>[n]());
  55 }
  56
  57 template<typename T, class... Args>
  58 typename uniquity<T>::verboten
  59 make_unique(Args&&...) = delete;
  60
  61 // The constexpr variant of std::max().
  62 template<class T>
  63 constexpr const T& max(const T& a, const T& b) {
  64   return a < b ? b : a;
  65 }
  66 } // namespace _backport14
  67
  68 namespace _backport17 {
  69 template <class C>
  70 constexpr auto size(const C& c) -> decltype(c.size()) {
  71   return c.size();
  72 }
  73
  74 template <typename T, std::size_t N>
  75 constexpr std::size_t size(const T (&array)[N]) noexcept {
  76   return N;
  77 }
  78 } // namespace _backport17
  79 using _backport14::make_unique;
  80 using _backport17::size;
  81 using _backport14::max;
  82 } // namespace ceph
  83
  84 #endif // CEPH_COMMON_BACKPORT14_H