1 /*
2  * Copyright (C) 2009 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.quicksearchbox;
18 
19 import android.os.SystemClock;
20 
21 /**
22  * Tracks latency in wall-clock time. Since {@link #getLatency} returns an {@code int},
23  * latencies over 2^31 ms (~ 25 days) cannot be measured.
24  * This class uses {@link SystemClock#uptimeMillis} which does not advance during deep sleep.
25  */
26 public class LatencyTracker {
27 
28     /**
29      * Start time, in milliseconds as returned by {@link SystemClock#uptimeMillis}.
30      */
31     private long mStartTime;
32 
33     /**
34      * Creates a new latency tracker and sets the start time.
35      */
LatencyTracker()36     public LatencyTracker() {
37         mStartTime = SystemClock.uptimeMillis();
38     }
39 
40     /**
41      * Resets the start time.
42      */
reset()43     public void reset() {
44         mStartTime = SystemClock.uptimeMillis();
45     }
46 
47     /**
48      * Gets the number of milliseconds since the object was created, or {@link #reset} was called.
49      */
getLatency()50     public int getLatency() {
51         long now = SystemClock.uptimeMillis();
52         return (int) (now - mStartTime);
53     }
54 
55 }
56