70 lines
1.8 KiB
C++
70 lines
1.8 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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#include <folly/detail/StaticSingletonManager.h>
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#include <mutex>
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#include <typeindex>
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#include <unordered_map>
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namespace folly {
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namespace detail {
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namespace {
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class StaticSingletonManagerWithRttiImpl {
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public:
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using Make = void*();
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using Cache = std::atomic<void*>;
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void* create(std::type_info const& key, Make& make, Cache& cache) {
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auto const ptr = entry(key).get(make);
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cache.store(ptr, std::memory_order_release);
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return ptr;
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}
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private:
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struct Entry {
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void* ptr{};
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std::mutex mutex;
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void* get(Make& make) {
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std::lock_guard<std::mutex> lock(mutex);
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return ptr ? ptr : (ptr = make());
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}
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};
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Entry& entry(std::type_info const& key) {
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std::lock_guard<std::mutex> lock(mutex_);
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auto& e = map_[key];
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return e ? *e : *(e = new Entry());
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}
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std::unordered_map<std::type_index, Entry*> map_;
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std::mutex mutex_;
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};
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} // namespace
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void* StaticSingletonManagerWithRtti::create_(Arg& arg) {
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// This Leaky Meyers Singleton must always live in the .cpp file.
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static auto& instance = *new StaticSingletonManagerWithRttiImpl();
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return instance.create(*arg.key, arg.make, arg.cache);
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}
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} // namespace detail
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} // namespace folly
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