--- /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