+++ /dev/null
-// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
-/*
- * This file is open source software, licensed to you under the terms
- * of the Apache License, Version 2.0 (the "License"). See the NOTICE file
- * distributed with this work for additional information regarding copyright
- * ownership. You may not use this file except in compliance with the License.
- *
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied. See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-/*
- * Copyright (C) 2014 Cloudius Systems, Ltd.
- */
-
-#ifndef CEPH_LW_SHARED_PTR_H_
-#define CEPH_LW_SHARED_PTR_H_
-
-#include <utility>
-#include <type_traits>
-#include <functional>
-#include <iostream>
-
-// This header defines two shared pointer facilities, lw_shared_ptr<>
-// modeled after std::shared_ptr<>.
-//
-// Unlike std::shared_ptr<>, neither of these implementations are thread
-// safe, and two pointers sharing the same object must not be used in
-// different threads.
-//
-// lw_shared_ptr<> is the more lightweight variant, with a lw_shared_ptr<>
-// occupying just one machine word, and adding just one word to the shared
-// object. However, it does not support polymorphism.
-//
-// Both variants support shared_from_this() via enable_shared_from_this<>
-// and lw_enable_shared_from_this<>().
-//
-
-template< class T >
-using remove_const_t = typename remove_const<T>::type;
-
-template <typename T>
-class lw_shared_ptr;
-
-template <typename T, typename... A>
-lw_shared_ptr<T> make_lw_shared(A&&... a);
-
-template <typename T>
-lw_shared_ptr<T> make_lw_shared(T&& a);
-
-template <typename T>
-lw_shared_ptr<T> make_lw_shared(T& a);
-
-// CRTP from this to enable shared_from_this:
-template <typename T>
-class enable_lw_shared_from_this {
- long _count = 0;
- using ctor = T;
- T* to_value() { return static_cast<T*>(this); }
- T* to_internal_object() { return static_cast<T*>(this); }
- protected:
- enable_lw_shared_from_this() noexcept {}
- enable_lw_shared_from_this(enable_lw_shared_from_this&&) noexcept {}
- enable_lw_shared_from_this(const enable_lw_shared_from_this&) noexcept {}
- enable_lw_shared_from_this& operator=(const enable_lw_shared_from_this&) noexcept { return *this; }
- enable_lw_shared_from_this& operator=(enable_lw_shared_from_this&&) noexcept { return *this; }
- public:
- lw_shared_ptr<T> shared_from_this();
- lw_shared_ptr<const T> shared_from_this() const;
- template <typename X>
- friend class lw_shared_ptr;
-};
-
-template <typename T>
-struct shared_ptr_no_esft {
- T _value;
- using ctor = shared_ptr_no_esft;
-
- T* to_value() { return &_value; }
- shared_ptr_no_esft* to_internal_object() { return this; }
- shared_ptr_no_esft() = default;
- shared_ptr_no_esft(const T& x) : _value(x) {}
- shared_ptr_no_esft(T&& x) : _value(std::move(x)) {}
- template <typename... A>
- shared_ptr_no_esft(A&&... a) : _value(std::forward<A>(a)...) {}
- template <typename X>
- friend class lw_shared_ptr;
-};
-
-template <typename T>
-using shared_ptr_impl = typename std::conditional<
- std::is_base_of<enable_lw_shared_from_this<remove_const_t<T>>, T>::value,
- enable_lw_shared_from_this<remove_const_t<T>>,
- shared_ptr_no_esft<remove_const_t<T>> >::type;
-
-template <typename T>
-class lw_shared_ptr {
- mutable shared_ptr_impl<T>* _p = nullptr;
- private:
- lw_shared_ptr(shared_ptr_impl<T>* p) noexcept : _p(p) {
- if (_p) {
- ++_p->_count;
- }
- }
- template <typename... A>
- static lw_shared_ptr make(A&&... a) {
- return lw_shared_ptr(new typename shared_ptr_impl<T>::ctor(std::forward<A>(a)...));
- }
- public:
- using element_type = T;
-
- lw_shared_ptr() noexcept = default;
- lw_shared_ptr(std::nullptr_t) noexcept : lw_shared_ptr() {}
- lw_shared_ptr(const lw_shared_ptr& x) noexcept : _p(x._p) {
- if (_p) {
- ++_p->_count;
- }
- }
- lw_shared_ptr(lw_shared_ptr&& x) noexcept : _p(x._p) {
- x._p = nullptr;
- }
- [[gnu::always_inline]]
- ~lw_shared_ptr() {
- if (_p && !--_p->_count) {
- delete _p->to_internal_object();
- }
- }
- lw_shared_ptr& operator=(const lw_shared_ptr& x) noexcept {
- if (_p != x._p) {
- this->~lw_shared_ptr();
- new (this) lw_shared_ptr(x);
- }
- return *this;
- }
- lw_shared_ptr& operator=(lw_shared_ptr&& x) noexcept {
- if (_p != x._p) {
- this->~lw_shared_ptr();
- new (this) lw_shared_ptr(std::move(x));
- }
- return *this;
- }
- lw_shared_ptr& operator=(std::nullptr_t) noexcept {
- return *this = lw_shared_ptr();
- }
- lw_shared_ptr& operator=(T&& x) noexcept {
- this->~lw_shared_ptr();
- new (this) lw_shared_ptr(make_lw_shared<T>(std::move(x)));
- return *this;
- }
-
- T& operator*() const noexcept { return *_p->to_value(); }
- T* operator->() const noexcept { return _p->to_value(); }
- T* get() const noexcept { return _p->to_value(); }
-
- long int use_count() const noexcept {
- if (_p) {
- return _p->_count;
- } else {
- return 0;
- }
- }
-
- operator lw_shared_ptr<const T>() const noexcept {
- return lw_shared_ptr<const T>(_p);
- }
-
- explicit operator bool() const noexcept {
- return _p;
- }
-
- bool owned() const noexcept {
- return _p->_count == 1;
- }
-
- bool operator==(const lw_shared_ptr<const T>& x) const {
- return _p == x._p;
- }
-
- bool operator!=(const lw_shared_ptr<const T>& x) const {
- return !operator==(x);
- }
-
- bool operator==(const lw_shared_ptr<remove_const_t<T>>& x) const {
- return _p == x._p;
- }
-
- bool operator!=(const lw_shared_ptr<remove_const_t<T>>& x) const {
- return !operator==(x);
- }
-
- template <typename U>
- friend class lw_shared_ptr;
-
- template <typename X, typename... A>
- friend lw_shared_ptr<X> make_lw_shared(A&&...);
-
- template <typename U>
- friend lw_shared_ptr<U> make_lw_shared(U&&);
-
- template <typename U>
- friend lw_shared_ptr<U> make_lw_shared(U&);
-
- template <typename U>
- friend class enable_lw_shared_from_this;
-};
-
-template <typename T, typename... A>
-inline
-lw_shared_ptr<T> make_lw_shared(A&&... a) {
- return lw_shared_ptr<T>::make(std::forward<A>(a)...);
-}
-
-template <typename T>
-inline
-lw_shared_ptr<T> make_lw_shared(T&& a) {
- return lw_shared_ptr<T>::make(std::move(a));
-}
-
-template <typename T>
-inline
-lw_shared_ptr<T> make_lw_shared(T& a) {
- return lw_shared_ptr<T>::make(a);
-}
-
-template <typename T>
-inline
-lw_shared_ptr<T>
-enable_lw_shared_from_this<T>::shared_from_this() {
- return lw_shared_ptr<T>(this);
-}
-
-template <typename T>
-inline
-lw_shared_ptr<const T>
-enable_lw_shared_from_this<T>::shared_from_this() const {
- return lw_shared_ptr<const T>(const_cast<enable_lw_shared_from_this*>(this));
-}
-
-template <typename T>
-static inline
-std::ostream& operator<<(std::ostream& out, const lw_shared_ptr<T>& p) {
- if (!p) {
- return out << "null";
- }
- return out << *p;
-}
-
-namespace std {
-
- template <typename T>
- struct hash<lw_shared_ptr<T>> : private hash<T*> {
- size_t operator()(const lw_shared_ptr<T>& p) const {
- return hash<T*>::operator()(p.get());
- }
- };
-
-}
-
-#endif /* CEPH_LW_SHARED_PTR_H_ */
Code Review / stor4nfv.git / blobdiff