CSE2410 Fall 2014 Bounce

// Copyright 2013 the V8 project authors. All rights reserved.

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are

// met:

//

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above

//       copyright notice, this list of conditions and the following

//       disclaimer in the documentation and/or other materials provided

//       with the distribution.

//     * Neither the name of Google Inc. nor the names of its

//       contributors may be used to endorse or promote products derived

//       from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef V8_PLATFORM_ELAPSED_TIMER_H_

#define V8_PLATFORM_ELAPSED_TIMER_H_

#include "../checks.h"

#include "time.h"

namespace v8 {

namespace internal {

class ElapsedTimer V8_FINAL BASE_EMBEDDED {

 public:

#ifdef DEBUG

  ElapsedTimer() : started_(false) {}

#endif

  // Starts this timer. Once started a timer can be checked with

  // |Elapsed()| or |HasExpired()|, and may be restarted using |Restart()|.

  // This method must not be called on an already started timer.

  void Start() {

    ASSERT(!IsStarted());

    start_ticks_ = Now();

#ifdef DEBUG

    started_ = true;

#endif

    ASSERT(IsStarted());

  }

  // Stops this timer. Must not be called on a timer that was not

  // started before.

  void Stop() {

    ASSERT(IsStarted());

    start_ticks_ = TimeTicks();

#ifdef DEBUG

    started_ = false;

#endif

    ASSERT(!IsStarted());

  }

  // Returns |true| if this timer was started previously.

  bool IsStarted() const {

    ASSERT(started_ || start_ticks_.IsNull());

    ASSERT(!started_ || !start_ticks_.IsNull());

    return !start_ticks_.IsNull();

  }

  // Restarts the timer and returns the time elapsed since the previous start.

  // This method is equivalent to obtaining the elapsed time with |Elapsed()|

  // and then starting the timer again, but does so in one single operation,

  // avoiding the need to obtain the clock value twice. It may only be called

  // on a previously started timer.

  TimeDelta Restart() {

    ASSERT(IsStarted());

    TimeTicks ticks = Now();

    TimeDelta elapsed = ticks - start_ticks_;

    ASSERT(elapsed.InMicroseconds() >= 0);

    start_ticks_ = ticks;

    ASSERT(IsStarted());

    return elapsed;

  }

  // Returns the time elapsed since the previous start. This method may only

  // be called on a previously started timer.

  TimeDelta Elapsed() const {

    ASSERT(IsStarted());

    TimeDelta elapsed = Now() - start_ticks_;

    ASSERT(elapsed.InMicroseconds() >= 0);

    return elapsed;

  }

  // Returns |true| if the specified |time_delta| has elapsed since the

  // previous start, or |false| if not. This method may only be called on

  // a previously started timer.

  bool HasExpired(TimeDelta time_delta) const {

    ASSERT(IsStarted());

    return Elapsed() >= time_delta;

  }

 private:

  static V8_INLINE TimeTicks Now() {

    TimeTicks now = TimeTicks::HighResolutionNow();

    ASSERT(!now.IsNull());

    return now;

  }

  TimeTicks start_ticks_;

#ifdef DEBUG

  bool started_;

#endif

};

} }  // namespace v8::internal

#endif  // V8_PLATFORM_ELAPSED_TIMER_H_