mirror of
https://github.com/ecency/ecency-mobile.git
synced 2024-12-24 05:42:33 +03:00
138 lines
3.5 KiB
C++
138 lines
3.5 KiB
C++
/*
|
|
* Copyright 2016 Facebook, Inc.
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* 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.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <atomic>
|
|
#include <cassert>
|
|
|
|
namespace folly {
|
|
|
|
/**
|
|
* A very simple atomic single-linked list primitive.
|
|
*
|
|
* Usage:
|
|
*
|
|
* class MyClass {
|
|
* AtomicIntrusiveLinkedListHook<MyClass> hook_;
|
|
* }
|
|
*
|
|
* AtomicIntrusiveLinkedList<MyClass, &MyClass::hook_> list;
|
|
* list.insert(&a);
|
|
* list.sweep([] (MyClass* c) { doSomething(c); }
|
|
*/
|
|
template <class T>
|
|
struct AtomicIntrusiveLinkedListHook {
|
|
T* next{nullptr};
|
|
};
|
|
|
|
template <class T, AtomicIntrusiveLinkedListHook<T> T::*HookMember>
|
|
class AtomicIntrusiveLinkedList {
|
|
public:
|
|
AtomicIntrusiveLinkedList() {}
|
|
AtomicIntrusiveLinkedList(const AtomicIntrusiveLinkedList&) = delete;
|
|
AtomicIntrusiveLinkedList& operator=(const AtomicIntrusiveLinkedList&) =
|
|
delete;
|
|
AtomicIntrusiveLinkedList(AtomicIntrusiveLinkedList&& other) noexcept {
|
|
auto tmp = other.head_.load();
|
|
other.head_ = head_.load();
|
|
head_ = tmp;
|
|
}
|
|
AtomicIntrusiveLinkedList& operator=(
|
|
AtomicIntrusiveLinkedList&& other) noexcept {
|
|
auto tmp = other.head_.load();
|
|
other.head_ = head_.load();
|
|
head_ = tmp;
|
|
|
|
return *this;
|
|
}
|
|
|
|
/**
|
|
* Note: list must be empty on destruction.
|
|
*/
|
|
~AtomicIntrusiveLinkedList() {
|
|
assert(empty());
|
|
}
|
|
|
|
bool empty() const {
|
|
return head_.load() == nullptr;
|
|
}
|
|
|
|
/**
|
|
* Atomically insert t at the head of the list.
|
|
* @return True if the inserted element is the only one in the list
|
|
* after the call.
|
|
*/
|
|
bool insertHead(T* t) {
|
|
assert(next(t) == nullptr);
|
|
|
|
auto oldHead = head_.load(std::memory_order_relaxed);
|
|
do {
|
|
next(t) = oldHead;
|
|
/* oldHead is updated by the call below.
|
|
|
|
NOTE: we don't use next(t) instead of oldHead directly due to
|
|
compiler bugs (GCC prior to 4.8.3 (bug 60272), clang (bug 18899),
|
|
MSVC (bug 819819); source:
|
|
http://en.cppreference.com/w/cpp/atomic/atomic/compare_exchange */
|
|
} while (!head_.compare_exchange_weak(oldHead, t,
|
|
std::memory_order_release,
|
|
std::memory_order_relaxed));
|
|
|
|
return oldHead == nullptr;
|
|
}
|
|
|
|
/**
|
|
* Repeatedly replaces the head with nullptr,
|
|
* and calls func() on the removed elements in the order from tail to head.
|
|
* Stops when the list is empty.
|
|
*/
|
|
template <typename F>
|
|
void sweep(F&& func) {
|
|
while (auto head = head_.exchange(nullptr)) {
|
|
auto rhead = reverse(head);
|
|
while (rhead != nullptr) {
|
|
auto t = rhead;
|
|
rhead = next(t);
|
|
next(t) = nullptr;
|
|
func(t);
|
|
}
|
|
}
|
|
}
|
|
|
|
private:
|
|
std::atomic<T*> head_{nullptr};
|
|
|
|
static T*& next(T* t) {
|
|
return (t->*HookMember).next;
|
|
}
|
|
|
|
/* Reverses a linked list, returning the pointer to the new head
|
|
(old tail) */
|
|
static T* reverse(T* head) {
|
|
T* rhead = nullptr;
|
|
while (head != nullptr) {
|
|
auto t = head;
|
|
head = next(t);
|
|
next(t) = rhead;
|
|
rhead = t;
|
|
}
|
|
return rhead;
|
|
}
|
|
};
|
|
|
|
} // namespace folly
|