FileObserver.java revision 60d8762413e8daba5f73559786312a9ec5e3b827 
1/*
2 * Copyright (C) 2006 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
17package android.os;
18
19import android.util.Log;
20
21import com.android.internal.os.RuntimeInit;
22
23import java.lang.ref.WeakReference;
24import java.util.ArrayList;
25import java.util.HashMap;
26
27public abstract class FileObserver {
28    /** File was accessed */
29    public static final int ACCESS = 0x00000001;
30    /** File was modified */
31    public static final int MODIFY = 0x00000002;
32    /** Metadata changed */
33    public static final int ATTRIB = 0x00000004;
34    /** Writable file was closed */
35    public static final int CLOSE_WRITE = 0x00000008;
36    /** Unwrittable file closed */
37    public static final int CLOSE_NOWRITE = 0x00000010;
38    /** File was opened */
39    public static final int OPEN = 0x00000020;
40    /** File was moved from X */
41    public static final int MOVED_FROM = 0x00000040;
42    /** File was moved to Y */
43    public static final int MOVED_TO = 0x00000080;
44    /** Subfile was created */
45    public static final int CREATE = 0x00000100;
46    /** Subfile was deleted */
47    public static final int DELETE = 0x00000200;
48    /** Self was deleted */
49    public static final int DELETE_SELF = 0x00000400;
50    /** Self was moved */
51    public static final int MOVE_SELF = 0x00000800;
52
53    public static final int ALL_EVENTS = ACCESS | MODIFY | ATTRIB | CLOSE_WRITE
54            | CLOSE_NOWRITE | OPEN | MOVED_FROM | MOVED_TO | DELETE | CREATE
55	    | DELETE_SELF | MOVE_SELF;
56
57    private static final String LOG_TAG = "FileObserver";
58
59    private static class ObserverThread extends Thread {
60	private HashMap<Integer, WeakReference> m_observers = new HashMap<Integer, WeakReference>();
61	private int m_fd;
62
63	public ObserverThread() {
64	    super("FileObserver");
65	    m_fd = init();
66	}
67
68	public void run() {
69	    observe(m_fd);
70	}
71
72	public int startWatching(String path, int mask, FileObserver observer) {
73	    int wfd = startWatching(m_fd, path, mask);
74
75	    Integer i = new Integer(wfd);
76	    if (wfd >= 0) {
77		synchronized (m_observers) {
78		    m_observers.put(i, new WeakReference(observer));
79		}
80	    }
81
82	    return i;
83	}
84
85	public void stopWatching(int descriptor) {
86	    stopWatching(m_fd, descriptor);
87	}
88
89    public void onEvent(int wfd, int mask, String path) {
90        // look up our observer, fixing up the map if necessary...
91        FileObserver observer;
92
93        synchronized (m_observers) {
94            WeakReference weak = m_observers.get(wfd);
95            observer = (FileObserver) weak.get();
96            if (observer == null) {
97                m_observers.remove(wfd);
98            }
99        }
100
101        // ...then call out to the observer without the sync lock held
102        if (observer != null) {
103            try {
104                observer.onEvent(mask, path);
105            } catch (Throwable throwable) {
106                Log.wtf(LOG_TAG, "Unhandled exception in FileObserver " + observer, throwable);
107            }
108        }
109    }
110
111	private native int init();
112	private native void observe(int fd);
113	private native int startWatching(int fd, String path, int mask);
114	private native void stopWatching(int fd, int wfd);
115    }
116
117    private static ObserverThread s_observerThread;
118
119    static {
120	s_observerThread = new ObserverThread();
121	s_observerThread.start();
122    }
123
124    // instance
125    private String m_path;
126    private Integer m_descriptor;
127    private int m_mask;
128
129    public FileObserver(String path) {
130	this(path, ALL_EVENTS);
131    }
132
133    public FileObserver(String path, int mask) {
134	m_path = path;
135	m_mask = mask;
136	m_descriptor = -1;
137    }
138
139    protected void finalize() {
140	stopWatching();
141    }
142
143    public void startWatching() {
144	if (m_descriptor < 0) {
145	    m_descriptor = s_observerThread.startWatching(m_path, m_mask, this);
146	}
147    }
148
149    public void stopWatching() {
150	if (m_descriptor >= 0) {
151	    s_observerThread.stopWatching(m_descriptor);
152	    m_descriptor = -1;
153	}
154    }
155
156    public abstract void onEvent(int event, String path);
157}
158