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.util;
18
19import java.io.FileDescriptor;
20import java.io.PrintWriter;
21import java.time.LocalDateTime;
22import java.util.ArrayDeque;
23import java.util.Deque;
24import java.util.Iterator;
25
26/**
27 * @hide
28 */
29public final class LocalLog {
30
31    private final Deque<String> mLog;
32    private final int mMaxLines;
33
34    public LocalLog(int maxLines) {
35        mMaxLines = Math.max(0, maxLines);
36        mLog = new ArrayDeque<>(mMaxLines);
37    }
38
39    public void log(String msg) {
40        if (mMaxLines <= 0) {
41            return;
42        }
43        append(String.format("%s - %s", LocalDateTime.now(), msg));
44    }
45
46    private synchronized void append(String logLine) {
47        while (mLog.size() >= mMaxLines) {
48            mLog.remove();
49        }
50        mLog.add(logLine);
51    }
52
53    public synchronized void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
54        Iterator<String> itr = mLog.iterator();
55        while (itr.hasNext()) {
56            pw.println(itr.next());
57        }
58    }
59
60    public synchronized void reverseDump(FileDescriptor fd, PrintWriter pw, String[] args) {
61        Iterator<String> itr = mLog.descendingIterator();
62        while (itr.hasNext()) {
63            pw.println(itr.next());
64        }
65    }
66
67    public static class ReadOnlyLocalLog {
68        private final LocalLog mLog;
69        ReadOnlyLocalLog(LocalLog log) {
70            mLog = log;
71        }
72        public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
73            mLog.dump(fd, pw, args);
74        }
75        public void reverseDump(FileDescriptor fd, PrintWriter pw, String[] args) {
76            mLog.reverseDump(fd, pw, args);
77        }
78    }
79
80    public ReadOnlyLocalLog readOnlyLocalLog() {
81        return new ReadOnlyLocalLog(this);
82    }
83}
84