initial code repo

[stor4nfv.git] / src / ceph / src / common / backport14.h

diff --git a/src/ceph/src/common/backport14.h b/src/ceph/src/common/backport14.h
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+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- 
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#include <memory>
+#include <type_traits>
+
+#ifndef CEPH_COMMON_BACKPORT14_H
+#define CEPH_COMMON_BACKPORT14_H
+
+// Library code from C++14 that can be implemented in C++11.
+
+namespace ceph {
+template<typename T>
+using remove_extent_t = typename std::remove_extent<T>::type;
+template<typename T>
+using remove_reference_t = typename std::remove_reference<T>::type;
+template<typename T>
+using result_of_t = typename std::result_of<T>::type;
+template<typename T>
+using decay_t = typename std::decay<T>::type;
+
+namespace _backport14 {
+template<typename T>
+struct uniquity {
+  using datum = std::unique_ptr<T>;
+};
+
+template<typename T>
+struct uniquity<T[]> {
+  using array = std::unique_ptr<T[]>;
+};
+
+template<typename T, std::size_t N>
+struct uniquity<T[N]> {
+  using verboten = void;
+};
+
+template<typename T, typename... Args>
+inline typename uniquity<T>::datum make_unique(Args&&... args) {
+  return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
+}
+
+template<typename T>
+inline typename uniquity<T>::array make_unique(std::size_t n) {
+  return std::unique_ptr<T>(new remove_extent_t<T>[n]());
+}
+
+template<typename T, class... Args>
+typename uniquity<T>::verboten
+make_unique(Args&&...) = delete;
+
+// The constexpr variant of std::max().
+template<class T>
+constexpr const T& max(const T& a, const T& b) {
+  return a < b ? b : a;
+}
+} // namespace _backport14
+
+namespace _backport17 {
+template <class C>
+constexpr auto size(const C& c) -> decltype(c.size()) {
+  return c.size();
+}
+
+template <typename T, std::size_t N>
+constexpr std::size_t size(const T (&array)[N]) noexcept {
+  return N;
+}
+
+/// http://en.cppreference.com/w/cpp/utility/functional/not_fn
+// this implementation uses c++14's result_of_t (above) instead of the c++17
+// invoke_result_t, and so may not behave correctly when SFINAE is required
+template <typename F>
+class not_fn_result {
+  using DecayF = decay_t<F>;
+  DecayF fn;
+ public:
+  explicit not_fn_result(F&& f) : fn(std::forward<F>(f)) {}
+  not_fn_result(not_fn_result&& f) = default;
+  not_fn_result(const not_fn_result& f) = default;
+
+  template<class... Args>
+  auto operator()(Args&&... args) &
+  -> decltype(!std::declval<result_of_t<DecayF&(Args...)>>()) {
+    return !fn(std::forward<Args>(args)...);
+  }
+  template<class... Args>
+  auto operator()(Args&&... args) const&
+  -> decltype(!std::declval<result_of_t<DecayF const&(Args...)>>()) {
+    return !fn(std::forward<Args>(args)...);
+  }
+
+  template<class... Args>
+  auto operator()(Args&&... args) &&
+  -> decltype(!std::declval<result_of_t<DecayF(Args...)>>()) {
+    return !std::move(fn)(std::forward<Args>(args)...);
+  }
+  template<class... Args>
+  auto operator()(Args&&... args) const&&
+  -> decltype(!std::declval<result_of_t<DecayF const(Args...)>>()) {
+    return !std::move(fn)(std::forward<Args>(args)...);
+  }
+};
+
+template <typename F>
+not_fn_result<F> not_fn(F&& fn) {
+  return not_fn_result<F>(std::forward<F>(fn));
+}
+
+} // namespace _backport17
+using _backport14::make_unique;
+using _backport17::size;
+using _backport14::max;
+using _backport17::not_fn;
+} // namespace ceph
+
+#endif // CEPH_COMMON_BACKPORT14_H