1 
2 /**
3  *    Copyright (C) 2018-present MongoDB, Inc.
4  *
5  *    This program is free software: you can redistribute it and/or modify
6  *    it under the terms of the Server Side Public License, version 1,
7  *    as published by MongoDB, Inc.
8  *
9  *    This program is distributed in the hope that it will be useful,
10  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
11  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  *    Server Side Public License for more details.
13  *
14  *    You should have received a copy of the Server Side Public License
15  *    along with this program. If not, see
16  *    <http://www.mongodb.com/licensing/server-side-public-license>.
17  *
18  *    As a special exception, the copyright holders give permission to link the
19  *    code of portions of this program with the OpenSSL library under certain
20  *    conditions as described in each individual source file and distribute
21  *    linked combinations including the program with the OpenSSL library. You
22  *    must comply with the Server Side Public License in all respects for
23  *    all of the code used other than as permitted herein. If you modify file(s)
24  *    with this exception, you may extend this exception to your version of the
25  *    file(s), but you are not obligated to do so. If you do not wish to do so,
26  *    delete this exception statement from your version. If you delete this
27  *    exception statement from all source files in the program, then also delete
28  *    it in the license file.
29  */
30 
31 #pragma once
32 
33 #include "mongo/util/time_support.h"
34 
35 namespace mongo {
36 
37 class TickSource;
38 
39 /**
40  * Time tracking object.
41  */
42 class Timer {
43 public:
44     /**
45      * Creates a timer with the system default tick source. Should not be created before global
46      * initialization completes.
47      */
48     Timer();
49 
50     /**
51      * Creates a timer using the specified tick source. Caller retains ownership of TickSource and
52      * must keep it in scope until Timer goes out of scope.
53      */
54     explicit Timer(TickSource* tickSource);
55 
micros()56     long long micros() const {
57         return static_cast<long long>((now() - _old) * _microsPerCount);
58     }
millis()59     int millis() const {
60         return static_cast<int>(micros() / 1000);
61     }
seconds()62     int seconds() const {
63         return static_cast<int>(micros() / 1000000);
64     }
minutes()65     int minutes() const {
66         return seconds() / 60;
67     }
68 
elapsed()69     Microseconds elapsed() const {
70         return Microseconds{micros()};
71     }
72 
reset()73     void reset() {
74         _old = now();
75     }
76 
77 private:
78     TickSource* const _tickSource;
79 
80     // Derived value from _countsPerSecond. This represents the conversion ratio
81     // from clock ticks to microseconds.
82     const double _microsPerCount;
83 
84     long long now() const;
85 
86     long long _old;
87 };
88 
89 }  // namespace mongo
90