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59 lines
1.9 KiB
59 lines
1.9 KiB
/*
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* Copyright (C) 2020 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/system_properties.h>
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#include <atomic>
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#include <condition_variable>
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#include <functional>
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#include <mutex>
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#include <string>
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#include <unordered_map>
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using PropertyMonitorCallback = bool(std::string value);
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struct PropertyMonitorData {
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std::function<PropertyMonitorCallback> callback;
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const prop_info* prop_info;
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uint32_t serial;
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};
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// This class is thread-unsafe: all operations must be guarded by mutexes if they can occur on
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// different threads.
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struct PropertyMonitor {
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PropertyMonitor() = default;
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~PropertyMonitor() = default;
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// Register a callback on a specified property, and immediately invoke it on the current value.
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// If the property is not defined, the callback will be invoked with the empty string.
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//
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// Only one callback can be registered on a property at once: subsequent registrations will
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// delete the original callback.
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void Add(std::string property, std::function<PropertyMonitorCallback> callback);
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// Run the PropertyMonitor indefinitely.
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//
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// This will run until a callback returns false. If a callback returns false, this does not
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// return immediately: it will run the other callbacks for changed properties first.
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void Run();
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private:
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std::unordered_map<std::string, PropertyMonitorData> properties_;
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uint32_t last_serial_ = 0;
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};
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