72 lines
2.0 KiB
C++
72 lines
2.0 KiB
C++
/*
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* Copyright (C) 2022 The Android Open Source Project
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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 <sys/epoll.h>
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#include <memory>
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#include <optional>
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#include <set>
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#include <shared_mutex>
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#include "common/libs/fs/shared_fd.h"
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#include "common/libs/utils/result.h"
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namespace cuttlefish {
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struct EpollEvent {
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SharedFD fd;
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uint32_t events;
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};
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class Epoll {
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public:
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static Result<Epoll> Create();
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Epoll(); // Invalid instance
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Epoll(Epoll&&);
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Epoll& operator=(Epoll&&);
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Result<void> Add(SharedFD fd, uint32_t events);
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Result<void> Modify(SharedFD fd, uint32_t events);
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Result<void> AddOrModify(SharedFD fd, uint32_t events);
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Result<void> Delete(SharedFD fd);
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Result<std::optional<EpollEvent>> Wait();
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private:
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Epoll(SharedFD);
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/**
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* This read-write mutex is read-locked to perform epoll operations, and
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* write-locked to replace the file descriptor.
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*
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* A read-write mutex is used here to make it possible to update the watched
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* set while the epoll resource is being waited on by another thread, while
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* excluding the possibility of the move constructor or assignment constructor
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* from stealing the file descriptor out from under waiting threads.
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*/
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std::shared_mutex epoll_mutex_;
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SharedFD epoll_fd_;
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/**
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* This read-write mutex is read-locked when interacting with it as a const
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* std::set, and write-locked when interacting with it as a std::set.
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*/
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std::shared_mutex watched_mutex_;
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std::set<SharedFD> watched_;
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};
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} // namespace cuttlefish
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