+++ /dev/null
-/*
- * 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_COMMON_DELETER_H
-#define CEPH_COMMON_DELETER_H
-
-#include <atomic>
-
-/// \addtogroup memory-module
-/// @{
-
-/// Provides a mechanism for managing the lifetime of a buffer.
-///
-/// A \c deleter is an object that is used to inform the consumer
-/// of some buffer (not referenced by the deleter itself) how to
-/// delete the buffer. This can be by calling an arbitrary function
-/// or destroying an object carried by the deleter. Examples of
-/// a deleter's encapsulated actions are:
-///
-/// - calling \c std::free(p) on some captured pointer, p
-/// - calling \c delete \c p on some captured pointer, p
-/// - decrementing a reference count somewhere
-///
-/// A deleter performs its action from its destructor.
-class deleter final {
- public:
- /// \cond internal
- struct impl;
- struct raw_object_tag {};
- /// \endcond
- private:
- // if bit 0 set, point to object to be freed directly.
- impl* _impl = nullptr;
- public:
- /// Constructs an empty deleter that does nothing in its destructor.
- deleter() = default;
- deleter(const deleter&) = delete;
- /// Moves a deleter.
- deleter(deleter&& x) noexcept : _impl(x._impl) { x._impl = nullptr; }
- /// \cond internal
- explicit deleter(impl* i) : _impl(i) {}
- deleter(raw_object_tag tag, void* object)
- : _impl(from_raw_object(object)) {}
- /// \endcond
- /// Destroys the deleter and carries out the encapsulated action.
- ~deleter();
- deleter& operator=(deleter&& x);
- deleter& operator=(deleter&) = delete;
- /// Performs a sharing operation. The encapsulated action will only
- /// be carried out after both the original deleter and the returned
- /// deleter are both destroyed.
- ///
- /// \return a deleter with the same encapsulated action as this one.
- deleter share();
- /// Checks whether the deleter has an associated action.
- explicit operator bool() const { return bool(_impl); }
- /// \cond internal
- void reset(impl* i) {
- this->~deleter();
- new (this) deleter(i);
- }
- /// \endcond
- /// Appends another deleter to this deleter. When this deleter is
- /// destroyed, both encapsulated actions will be carried out.
- void append(deleter d);
- private:
- static bool is_raw_object(impl* i) {
- auto x = reinterpret_cast<uintptr_t>(i);
- return x & 1;
- }
- bool is_raw_object() const {
- return is_raw_object(_impl);
- }
- static void* to_raw_object(impl* i) {
- auto x = reinterpret_cast<uintptr_t>(i);
- return reinterpret_cast<void*>(x & ~uintptr_t(1));
- }
- void* to_raw_object() const {
- return to_raw_object(_impl);
- }
- impl* from_raw_object(void* object) {
- auto x = reinterpret_cast<uintptr_t>(object);
- return reinterpret_cast<impl*>(x | 1);
- }
-};
-
-/// \cond internal
-struct deleter::impl {
- std::atomic_uint refs;
- deleter next;
- impl(deleter next) : refs(1), next(std::move(next)) {}
- virtual ~impl() {}
-};
-/// \endcond
-
-inline deleter::~deleter() {
- if (is_raw_object()) {
- std::free(to_raw_object());
- return;
- }
- if (_impl && --_impl->refs == 0) {
- delete _impl;
- }
-}
-
-inline deleter& deleter::operator=(deleter&& x) {
- if (this != &x) {
- this->~deleter();
- new (this) deleter(std::move(x));
- }
- return *this;
-}
-
-/// \cond internal
-template <typename Deleter>
-struct lambda_deleter_impl final : deleter::impl {
- Deleter del;
- lambda_deleter_impl(deleter next, Deleter&& del)
- : impl(std::move(next)), del(std::move(del)) {}
- ~lambda_deleter_impl() override { del(); }
-};
-
-template <typename Object>
-struct object_deleter_impl final : deleter::impl {
- Object obj;
- object_deleter_impl(deleter next, Object&& obj)
- : impl(std::move(next)), obj(std::move(obj)) {}
-};
-
-template <typename Object>
-inline
-object_deleter_impl<Object>* make_object_deleter_impl(deleter next, Object obj) {
- return new object_deleter_impl<Object>(std::move(next), std::move(obj));
-}
-/// \endcond
-
-/// Makes a \ref deleter that encapsulates the action of
-/// destroying an object, as well as running another deleter. The input
-/// object is moved to the deleter, and destroyed when the deleter is destroyed.
-///
-/// \param d deleter that will become part of the new deleter's encapsulated action
-/// \param o object whose destructor becomes part of the new deleter's encapsulated action
-/// \related deleter
-template <typename Object>
-deleter make_deleter(deleter next, Object o) {
- return deleter(new lambda_deleter_impl<Object>(std::move(next), std::move(o)));
-}
-
-/// Makes a \ref deleter that encapsulates the action of destroying an object. The input
-/// object is moved to the deleter, and destroyed when the deleter is destroyed.
-///
-/// \param o object whose destructor becomes the new deleter's encapsulated action
-/// \related deleter
-template <typename Object>
-deleter make_deleter(Object o) {
- return make_deleter(deleter(), std::move(o));
-}
-
-/// \cond internal
-struct free_deleter_impl final : deleter::impl {
- void* obj;
- free_deleter_impl(void* obj) : impl(deleter()), obj(obj) {}
- ~free_deleter_impl() override { std::free(obj); }
-};
-/// \endcond
-
-inline deleter deleter::share() {
- if (!_impl) {
- return deleter();
- }
- if (is_raw_object()) {
- _impl = new free_deleter_impl(to_raw_object());
- }
- ++_impl->refs;
- return deleter(_impl);
-}
-
-// Appends 'd' to the chain of deleters. Avoids allocation if possible. For
-// performance reasons the current chain should be shorter and 'd' should be
-// longer.
-inline void deleter::append(deleter d) {
- if (!d._impl) {
- return;
- }
- impl* next_impl = _impl;
- deleter* next_d = this;
- while (next_impl) {
- if (next_impl == d._impl)
- return ;
- if (is_raw_object(next_impl)) {
- next_d->_impl = next_impl = new free_deleter_impl(to_raw_object(next_impl));
- }
- if (next_impl->refs != 1) {
- next_d->_impl = next_impl = make_object_deleter_impl(std::move(next_impl->next), deleter(next_impl));
- }
- next_d = &next_impl->next;
- next_impl = next_d->_impl;
- }
- next_d->_impl = d._impl;
- d._impl = nullptr;
-}
-
-/// Makes a deleter that calls \c std::free() when it is destroyed.
-///
-/// \param obj object to free.
-/// \related deleter
-inline deleter make_free_deleter(void* obj) {
- if (!obj) {
- return deleter();
- }
- return deleter(deleter::raw_object_tag(), obj);
-}
-
-/// Makes a deleter that calls \c std::free() when it is destroyed, as well
-/// as invoking the encapsulated action of another deleter.
-///
-/// \param d deleter to invoke.
-/// \param obj object to free.
-/// \related deleter
-inline deleter make_free_deleter(deleter next, void* obj) {
- return make_deleter(std::move(next), [obj] () mutable { std::free(obj); });
-}
-
-/// \see make_deleter(Object)
-/// \related deleter
-template <typename T>
-inline deleter make_object_deleter(T&& obj) {
- return deleter{make_object_deleter_impl(deleter(), std::move(obj))};
-}
-
-/// \see make_deleter(deleter, Object)
-/// \related deleter
-template <typename T>
-inline deleter make_object_deleter(deleter d, T&& obj) {
- return deleter{make_object_deleter_impl(std::move(d), std::move(obj))};
-}
-
-/// @}
-
-#endif /* CEPH_COMMON_DELETER_H */
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