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      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.camera.device;
     18 
     19 import com.android.camera.async.Lifetime;
     20 import com.google.common.util.concurrent.ListenableFuture;
     21 
     22 import javax.annotation.Nullable;
     23 import javax.annotation.concurrent.GuardedBy;
     24 
     25 /**
     26  * This class manages the lifecycle of a single device and API version.
     27  * A single instance deals with multiple requests for the same device
     28  * by canceling previous, uncompleted future requests, and tolerates
     29  * multiple calls to open() and close(). Once the device reaches the
     30  * shutdown phase (Defined as a close event with no pending open
     31  * requests) The object is no longer useful and a new instance should
     32  * be created.
     33  */
     34 public class CameraDeviceLifecycle<TDevice> implements
     35       SingleDeviceLifecycle<TDevice, CameraDeviceKey> {
     36 
     37     private final Object mLock;
     38     private final CameraDeviceKey mDeviceKey;
     39 
     40     @GuardedBy("mLock")
     41     private final SingleDeviceStateMachine<TDevice, CameraDeviceKey> mDeviceState;
     42 
     43     @Nullable
     44     @GuardedBy("mLock")
     45     private SingleDeviceRequest<TDevice> mDeviceRequest;
     46 
     47     // TODO: Consider passing in parent lifetime to ensure this is
     48     // ALWAYS shut down.
     49     public CameraDeviceLifecycle(CameraDeviceKey cameraDeviceKey,
     50           SingleDeviceStateMachine<TDevice, CameraDeviceKey> deviceState) {
     51         mDeviceKey = cameraDeviceKey;
     52         mDeviceState = deviceState;
     53         mLock = new Object();
     54     }
     55 
     56     @Override
     57     public CameraDeviceKey getId() {
     58         return mDeviceKey;
     59     }
     60 
     61     @Override
     62     public ListenableFuture<TDevice> createRequest(Lifetime lifetime) {
     63         synchronized (mLock) {
     64             mDeviceRequest = new SingleDeviceRequest<>(lifetime);
     65             lifetime.add(mDeviceRequest);
     66             mDeviceState.setRequest(mDeviceRequest);
     67 
     68             return mDeviceRequest.getFuture();
     69         }
     70     }
     71 
     72     /**
     73      * Request that the device represented by this lifecycle should
     74      * attempt to reach an open state.
     75      */
     76     @Override
     77     public void open() {
     78         synchronized (mLock) {
     79             mDeviceState.requestOpen();
     80         }
     81     }
     82 
     83     /**
     84      * Request that the device represented by this lifecycle should
     85      * attempt to reach a closed state.
     86      */
     87     @Override
     88     public void close() {
     89         synchronized (mLock) {
     90             if (mDeviceRequest != null) {
     91                 mDeviceRequest.close();
     92                 mDeviceRequest = null;
     93             }
     94             mDeviceState.requestClose();
     95         }
     96     }
     97 }
     98