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.messaging.util;
18 
19 
20 import android.annotation.TargetApi;
21 import android.os.Build;
22 
23 /**
24  * Helper class for systrace (see http://developer.android.com/tools/help/systrace.html).<p>
25  * To enable, set log.tag.Bugle_Trace (defined by {@link #TAG} to VERBOSE before
26  * the process starts.<p>
27  * Note that this will run only on JBMR2 or later; on earlier platforms or if the log
28  * tag isn't set, calls to {@link #beginSection(String)} or {@link #endSection()} are no-ops. <p>
29  * Internally, calls dispatch to either a class that actually does work or a class that doesn't.
30  * This avoids Dalvik complaining when it loads the class on earlier platforms that the
31  * opcodes aren't available, and, according to the Dalvik team, using vtable dispatching for
32  * something like this should be faster than if (OsUtil.isAtLeast...()) on each call.
33  */
34 public final class Trace {
35     private static final String TAG = "Bugle_Trace";
36     private abstract static class AbstractTrace {
beginSection(String sectionName)37         abstract void beginSection(String sectionName);
endSection()38         abstract void endSection();
39     }
40 
41     private static final AbstractTrace sTrace;
42 
43     // Static initializer to pick the correct trace class to handle tracing.
44     static {
45         // Use android.util.Log instead of LogUtil here to avoid pulling in Gservices
46         // too early in app startup.
47         if (OsUtil.isAtLeastJB_MR2() &&
48                 android.util.Log.isLoggable(TAG, android.util.Log.VERBOSE)) {
49             sTrace = new TraceJBMR2();
50         } else {
51             sTrace = new TraceShim();
52         }
53     }
54 
55     /**
56      * Writes a trace message to indicate that a given section of code has begun. This call must
57      * be followed by a corresponding call to {@link #endSection()} on the same thread.
58      *
59      * <p class="note"> At this time the vertical bar character '|', newline character '\n', and
60      * null character '\0' are used internally by the tracing mechanism.  If sectionName contains
61      * these characters they will be replaced with a space character in the trace.
62      *
63      * @param sectionName The name of the code section to appear in the trace.  This may be at
64      * most 127 Unicode code units long.
65      */
beginSection(String sectionName)66     public static void beginSection(String sectionName) {
67         if (LogUtil.isLoggable(TAG, LogUtil.VERBOSE)) {
68             LogUtil.v(TAG, "beginSection() " + sectionName);
69         }
70         sTrace.beginSection(sectionName);
71     }
72 
73     /**
74      * Writes a trace message to indicate that a given section of code has ended. This call must
75      * be preceeded by a corresponding call to {@link #beginSection(String)}. Calling this method
76      * will mark the end of the most recently begun section of code, so care must be taken to
77      * ensure that beginSection / endSection pairs are properly nested and called from the same
78      * thread.
79      */
endSection()80     public static void endSection() {
81         sTrace.endSection();
82         if (LogUtil.isLoggable(TAG, LogUtil.VERBOSE)) {
83             LogUtil.v(TAG, "endSection()");
84         }
85     }
86 
87     /**
88      * Internal class that we use if we really did enable tracing.
89      */
90     @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR2)
91     private static final class TraceJBMR2 extends AbstractTrace {
92         @Override
beginSection(String sectionName)93         void beginSection(String sectionName) {
94             android.os.Trace.beginSection(sectionName);
95         }
96 
97         @Override
endSection()98         void endSection() {
99             android.os.Trace.endSection();
100         }
101     }
102 
103     /**
104      * Placeholder class that we use if we aren't really tracing.
105      */
106     private static final class TraceShim extends AbstractTrace {
107         @Override
beginSection(String sectionName)108         void beginSection(String sectionName) {
109         }
110 
111         @Override
endSection()112         void endSection() {
113         }
114     }
115 }
116