113 lines
3.2 KiB
C++
113 lines
3.2 KiB
C++
/*
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* Copyright (C) 2017 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <wtf/Atomics.h>
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#include <wtf/Noncopyable.h>
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namespace WTF {
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// This a simple single consumer, multiple producer Bag data structure.
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template<typename T>
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class LocklessBag final {
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WTF_MAKE_FAST_ALLOCATED;
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WTF_MAKE_NONCOPYABLE(LocklessBag);
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public:
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struct Node {
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WTF_MAKE_FAST_ALLOCATED;
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public:
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T data;
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Node* next;
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};
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LocklessBag()
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: m_head(nullptr)
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{
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}
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enum PushResult { Empty, NonEmpty };
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PushResult add(T&& element)
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{
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Node* newNode = new Node();
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newNode->data = std::forward<T>(element);
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Node* oldHead;
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m_head.transaction([&] (Node*& head) {
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oldHead = head;
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newNode->next = head;
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head = newNode;
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return true;
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});
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return oldHead == nullptr ? Empty : NonEmpty;
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}
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// CONSUMER FUNCTIONS: Everything below here is only safe to call from the consumer thread.
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// This function is actually safe to call from more than one thread, but ONLY if no thread can call consumeAll.
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template<typename Functor>
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void iterate(const Functor& func)
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{
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Node* node = m_head.load();
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while (node) {
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const T& data = node->data;
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func(data);
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node = node->next;
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}
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}
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template<typename Functor>
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void consumeAll(const Functor& func)
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{
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consumeAllWithNode([&] (T&& data, Node* node) {
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func(WTFMove(data));
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delete node;
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});
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}
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template<typename Functor>
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void consumeAllWithNode(const Functor& func)
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{
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Node* node = m_head.exchange(nullptr);
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while (node) {
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Node* oldNode = node;
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node = node->next;
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func(WTFMove(oldNode->data), oldNode);
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}
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}
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~LocklessBag()
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{
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consumeAll([] (T&&) { });
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}
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private:
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Atomic<Node*> m_head;
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};
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} // namespace WTF
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