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.
CameraDeviceLifecycle(CameraDeviceKey cameraDeviceKey, SingleDeviceStateMachine<TDevice, CameraDeviceKey> deviceState)49     public CameraDeviceLifecycle(CameraDeviceKey cameraDeviceKey,
50           SingleDeviceStateMachine<TDevice, CameraDeviceKey> deviceState) {
51         mDeviceKey = cameraDeviceKey;
52         mDeviceState = deviceState;
53         mLock = new Object();
54     }
55 
56     @Override
getId()57     public CameraDeviceKey getId() {
58         return mDeviceKey;
59     }
60 
61     @Override
createRequest(Lifetime lifetime)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
open()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
close()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