IoTracker.java revision 118de16ee0529955eaca8cc5ce864cac49598c86 
1/*
2 * Copyright (C) 2016 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 libcore.io;
18
19import dalvik.system.BlockGuard;
20
21/**
22 * Used to detect unbuffered I/O.
23 * @hide
24 */
25public final class IoTracker {
26    private int opCount;
27    private int totalByteCount;
28    private boolean isOpen = true;
29    private Mode mode = Mode.READ;
30
31    public void trackIo(int byteCount) {
32        ++opCount;
33        totalByteCount += byteCount;
34        if (isOpen && opCount > 10 && totalByteCount < 10*512) {
35            BlockGuard.getThreadPolicy().onUnbufferedIO();
36            isOpen = false;
37        }
38    }
39
40    public void trackIo(int byteCount, Mode mode) {
41        if (this.mode != mode) {
42            reset();
43            this.mode = mode;
44        }
45        trackIo(byteCount);
46    }
47
48    /**
49     * Resets the state of the IoTracker, except {@link #isOpen} as it is not required to notify
50     * again and again about the same stream.
51     * This is primarily used by RandomAccessFile to consider a case when {@link
52     * java.io.RandomAccessFile#seek seek} is called.
53     */
54    public void reset() {
55        opCount = 0;
56        totalByteCount = 0;
57    }
58
59    public enum Mode {
60        READ,
61        WRITE
62    }
63}
64