73 lines
2.3 KiB
C++
73 lines
2.3 KiB
C++
/*
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* 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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*/
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#pragma once
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#include <map>
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#include <folly/ThreadLocal.h>
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#include <folly/executors/GlobalExecutor.h>
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#include <folly/io/async/EventBase.h>
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namespace folly {
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/*
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* IOObjectCache manages objects of type T that are dependent on an EventBase
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* provided by the global IOExecutor.
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*
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* Provide a factory that creates T objects given an EventBase, and get() will
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* lazily create T objects based on an EventBase from the global IOExecutor.
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* These are stored thread locally - for a given pair of event base and calling
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* thread there will only be one T object created.
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*
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* The primary use case is for managing objects that need to do async IO on an
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* event base (e.g. thrift clients) that can be used outside the IO thread
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* without much hassle. For instance, you could use this to manage Thrift
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* clients that are only ever called from within other threads without the
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* calling thread needing to know anything about the IO threads that the clients
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* will do their work on.
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*/
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template <class T>
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class IOObjectCache {
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public:
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typedef std::function<std::shared_ptr<T>(folly::EventBase*)> TFactory;
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IOObjectCache() = default;
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explicit IOObjectCache(TFactory factory) : factory_(std::move(factory)) {}
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std::shared_ptr<T> get() {
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CHECK(factory_);
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auto eb = getIOExecutor()->getEventBase();
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CHECK(eb);
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auto it = cache_->find(eb);
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if (it == cache_->end()) {
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auto p = cache_->insert(std::make_pair(eb, factory_(eb)));
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it = p.first;
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}
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return it->second;
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}
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void setFactory(TFactory factory) {
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factory_ = std::move(factory);
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}
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private:
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folly::ThreadLocal<std::map<folly::EventBase*, std::shared_ptr<T>>> cache_;
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TFactory factory_;
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};
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} // namespace folly
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