141 lines
3.7 KiB
C++
141 lines
3.7 KiB
C++
// Copyright (c) Facebook, Inc. and its affiliates.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#pragma once
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#include <atomic>
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#include <functional>
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#include <mutex>
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#include "yarpl/Refcounted.h"
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#include "yarpl/single/SingleSubscription.h"
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namespace yarpl {
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namespace single {
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/**
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* Implementation that allows checking if a Subscription is cancelled.
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*/
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class AtomicBoolSingleSubscription : public SingleSubscription {
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public:
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void cancel() override {
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cancelled_ = true;
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}
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bool isCancelled() const {
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return cancelled_;
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}
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private:
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std::atomic_bool cancelled_{false};
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};
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/**
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* Implementation that gets a callback when cancellation occurs.
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*/
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class CallbackSingleSubscription : public SingleSubscription {
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public:
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explicit CallbackSingleSubscription(std::function<void()> onCancel)
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: onCancel_(std::move(onCancel)) {}
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void cancel() override {
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bool expected = false;
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// mark cancelled 'true' and only if successful invoke 'onCancel()'
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if (cancelled_.compare_exchange_strong(expected, true)) {
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onCancel_();
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}
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}
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bool isCancelled() const {
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return cancelled_;
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}
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private:
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std::atomic_bool cancelled_{false};
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std::function<void()> onCancel_;
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};
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/**
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* Implementation that can be cancelled with or without
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* a delegate, and when the delegate exists (before or after cancel)
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* it will be cancelled in a thread-safe manner.
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*/
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class DelegateSingleSubscription : public SingleSubscription {
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public:
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explicit DelegateSingleSubscription() {}
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void cancel() override {
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bool shouldCancelDelegate = false;
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{
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std::lock_guard<std::mutex> g(m_);
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cancelled_ = true;
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if (delegate_) {
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shouldCancelDelegate = true;
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}
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}
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// cancel without holding lock
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if (shouldCancelDelegate) {
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delegate_->cancel();
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}
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}
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bool isCancelled() const {
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std::lock_guard<std::mutex> g(m_);
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return cancelled_;
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}
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/**
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* This can be called once.
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*/
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void setDelegate(std::shared_ptr<SingleSubscription> d) {
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bool shouldCancelDelegate = false;
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{
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std::lock_guard<std::mutex> g(m_);
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if (delegate_) {
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throw std::runtime_error("Delegate already set. Only one permitted.");
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}
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delegate_ = std::move(d);
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if (cancelled_) {
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shouldCancelDelegate = true;
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}
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}
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// cancel without holding lock
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if (shouldCancelDelegate) {
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delegate_->cancel();
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}
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}
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private:
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// all must be protected by a mutex
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mutable std::mutex m_;
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bool cancelled_{false};
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std::shared_ptr<SingleSubscription> delegate_;
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};
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class SingleSubscriptions {
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public:
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static std::shared_ptr<CallbackSingleSubscription> create(
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std::function<void()> onCancel) {
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return std::make_shared<CallbackSingleSubscription>(std::move(onCancel));
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}
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static std::shared_ptr<CallbackSingleSubscription> create(
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std::atomic_bool& cancelled) {
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return create([&cancelled]() { cancelled = true; });
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}
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static std::shared_ptr<SingleSubscription> empty() {
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return std::make_shared<AtomicBoolSingleSubscription>();
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}
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static std::shared_ptr<AtomicBoolSingleSubscription>
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atomicBoolSubscription() {
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return std::make_shared<AtomicBoolSingleSubscription>();
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}
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};
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} // namespace single
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} // namespace yarpl
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