Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 1 | // Copyright 2013 the V8 project authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef V8_BASE_PLATFORM_ELAPSED_TIMER_H_ |
| 6 | #define V8_BASE_PLATFORM_ELAPSED_TIMER_H_ |
| 7 | |
| 8 | #include "src/base/logging.h" |
| 9 | #include "src/base/platform/time.h" |
| 10 | |
| 11 | namespace v8 { |
| 12 | namespace base { |
| 13 | |
| 14 | class ElapsedTimer FINAL { |
| 15 | public: |
| 16 | #ifdef DEBUG |
| 17 | ElapsedTimer() : started_(false) {} |
| 18 | #endif |
| 19 | |
| 20 | // Starts this timer. Once started a timer can be checked with |
| 21 | // |Elapsed()| or |HasExpired()|, and may be restarted using |Restart()|. |
| 22 | // This method must not be called on an already started timer. |
| 23 | void Start() { |
| 24 | DCHECK(!IsStarted()); |
| 25 | start_ticks_ = Now(); |
| 26 | #ifdef DEBUG |
| 27 | started_ = true; |
| 28 | #endif |
| 29 | DCHECK(IsStarted()); |
| 30 | } |
| 31 | |
| 32 | // Stops this timer. Must not be called on a timer that was not |
| 33 | // started before. |
| 34 | void Stop() { |
| 35 | DCHECK(IsStarted()); |
| 36 | start_ticks_ = TimeTicks(); |
| 37 | #ifdef DEBUG |
| 38 | started_ = false; |
| 39 | #endif |
| 40 | DCHECK(!IsStarted()); |
| 41 | } |
| 42 | |
| 43 | // Returns |true| if this timer was started previously. |
| 44 | bool IsStarted() const { |
| 45 | DCHECK(started_ || start_ticks_.IsNull()); |
| 46 | DCHECK(!started_ || !start_ticks_.IsNull()); |
| 47 | return !start_ticks_.IsNull(); |
| 48 | } |
| 49 | |
| 50 | // Restarts the timer and returns the time elapsed since the previous start. |
| 51 | // This method is equivalent to obtaining the elapsed time with |Elapsed()| |
| 52 | // and then starting the timer again, but does so in one single operation, |
| 53 | // avoiding the need to obtain the clock value twice. It may only be called |
| 54 | // on a previously started timer. |
| 55 | TimeDelta Restart() { |
| 56 | DCHECK(IsStarted()); |
| 57 | TimeTicks ticks = Now(); |
| 58 | TimeDelta elapsed = ticks - start_ticks_; |
| 59 | DCHECK(elapsed.InMicroseconds() >= 0); |
| 60 | start_ticks_ = ticks; |
| 61 | DCHECK(IsStarted()); |
| 62 | return elapsed; |
| 63 | } |
| 64 | |
| 65 | // Returns the time elapsed since the previous start. This method may only |
| 66 | // be called on a previously started timer. |
| 67 | TimeDelta Elapsed() const { |
| 68 | DCHECK(IsStarted()); |
| 69 | TimeDelta elapsed = Now() - start_ticks_; |
| 70 | DCHECK(elapsed.InMicroseconds() >= 0); |
| 71 | return elapsed; |
| 72 | } |
| 73 | |
| 74 | // Returns |true| if the specified |time_delta| has elapsed since the |
| 75 | // previous start, or |false| if not. This method may only be called on |
| 76 | // a previously started timer. |
| 77 | bool HasExpired(TimeDelta time_delta) const { |
| 78 | DCHECK(IsStarted()); |
| 79 | return Elapsed() >= time_delta; |
| 80 | } |
| 81 | |
| 82 | private: |
| 83 | static V8_INLINE TimeTicks Now() { |
| 84 | TimeTicks now = TimeTicks::HighResolutionNow(); |
| 85 | DCHECK(!now.IsNull()); |
| 86 | return now; |
| 87 | } |
| 88 | |
| 89 | TimeTicks start_ticks_; |
| 90 | #ifdef DEBUG |
| 91 | bool started_; |
| 92 | #endif |
| 93 | }; |
| 94 | |
| 95 | } } // namespace v8::base |
| 96 | |
| 97 | #endif // V8_BASE_PLATFORM_ELAPSED_TIMER_H_ |