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76 lines
2.4 KiB
76 lines
2.4 KiB
4 months ago
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/*
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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 <mutex>
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#include <binder/IBinder.h>
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#include <utils/StrongPointer.h>
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namespace android {
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namespace media {
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// Must be pre-declared, or else there isn't a good way to generate a header
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// library.
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class ICaptureStateListener;
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}
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// A utility for managing capture state change notifications.
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//
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// We are making some strong assumptions, for the sake of simplicity:
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// - There is no way to explicitly unregister listeners. The only way for a
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// listener to unregister is by dying.
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// - There's only at most one listener at a given time. Attempting to register
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// a second listener will cause a crash.
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// - This class isn't really meant to ever be destroyed. We expose a destructor
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// because it is convenient to use this class as a global instance or a member
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// of another class, but it will crash if destroyed while a listener is
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// registered.
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//
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// All of these assumptions can be lifted if there is ever a need.
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//
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// This class is thread-safe.
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class CaptureStateNotifier {
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public:
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// Ctor.
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// Accepts the initial active state.
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explicit CaptureStateNotifier(bool initialActive);
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// Register a listener to be notified of state changes.
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// The current state is returned and from that point on any change will be
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// notified of.
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bool RegisterListener(const sp<media::ICaptureStateListener>& listener);
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// Change the current capture state.
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// Active means "actively capturing".
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void setCaptureState(bool active);
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// Dtor. Do not actually call at runtime. Will cause a crash if a listener
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// is registered.
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~CaptureStateNotifier();
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private:
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std::mutex mMutex;
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sp<media::ICaptureStateListener> mListener;
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sp<IBinder::DeathRecipient> mDeathRecipient;
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bool mActive;
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class DeathRecipient;
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void binderDied();
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};
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} // namespace android
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