C++ TimeDuration::IsZero方法代码示例

void
TimeoutManager::RunTimeout(const TimeStamp& aNow, const TimeStamp& aTargetDeadline)
{
  MOZ_DIAGNOSTIC_ASSERT(!aNow.IsNull());
  MOZ_DIAGNOSTIC_ASSERT(!aTargetDeadline.IsNull());

  MOZ_ASSERT_IF(mWindow.IsFrozen(), mWindow.IsSuspended());
  if (mWindow.IsSuspended()) {
    return;
  }

  // Limit the overall time spent in RunTimeout() to reduce jank.
  uint32_t totalTimeLimitMS = std::max(1u, gMaxConsecutiveCallbacksMilliseconds);
  const TimeDuration totalTimeLimit =
    TimeDuration::Min(TimeDuration::FromMilliseconds(totalTimeLimitMS),
                      TimeDuration::Max(TimeDuration(), mExecutionBudget));

  // Allow up to 25% of our total time budget to be used figuring out which
  // timers need to run.  This is the initial loop in this method.
  const TimeDuration initialTimeLimit =
    TimeDuration::FromMilliseconds(totalTimeLimit.ToMilliseconds() / 4);

  // Ammortize overhead from from calling TimeStamp::Now() in the initial
  // loop, though, by only checking for an elapsed limit every N timeouts.
  const uint32_t kNumTimersPerInitialElapsedCheck = 100;

  // Start measuring elapsed time immediately.  We won't potentially expire
  // the time budget until at least one Timeout has run, though.
  TimeStamp now(aNow);
  TimeStamp start = now;

  uint32_t firingId = CreateFiringId();
  auto guard = MakeScopeExit([&] {
    DestroyFiringId(firingId);
  });

  // Make sure that the window and the script context don't go away as
  // a result of running timeouts
  nsCOMPtr<nsIScriptGlobalObject> windowKungFuDeathGrip(&mWindow);
  // Silence the static analysis error about windowKungFuDeathGrip.  Accessing
  // members of mWindow here is safe, because the lifetime of TimeoutManager is
  // the same as the lifetime of the containing nsGlobalWindow.
  Unused << windowKungFuDeathGrip;

  // A native timer has gone off. See which of our timeouts need
  // servicing
  TimeStamp deadline;

  if (aTargetDeadline > now) {
    // The OS timer fired early (which can happen due to the timers
    // having lower precision than TimeStamp does).  Set |deadline| to
    // be the time when the OS timer *should* have fired so that any
    // timers that *should* have fired *will* be fired now.

    deadline = aTargetDeadline;
  } else {
    deadline = now;
  }

  TimeStamp nextDeadline;
  uint32_t numTimersToRun = 0;

  // The timeout list is kept in deadline order. Discover the latest timeout
  // whose deadline has expired. On some platforms, native timeout events fire
  // "early", but we handled that above by setting deadline to aTargetDeadline
  // if the timer fired early.  So we can stop walking if we get to timeouts
  // whose When() is greater than deadline, since once that happens we know
  // nothing past that point is expired.
  {
    // Use a nested scope in order to make sure the strong references held by
    // the iterator are freed after the loop.
    OrderedTimeoutIterator expiredIter(mNormalTimeouts, mTrackingTimeouts);

    while (true) {
      Timeout* timeout = expiredIter.Next();
      if (!timeout || totalTimeLimit.IsZero() || timeout->When() > deadline) {
        if (timeout) {
          nextDeadline = timeout->When();
        }
        break;
      }

      if (IsInvalidFiringId(timeout->mFiringId)) {
        // Mark any timeouts that are on the list to be fired with the
        // firing depth so that we can reentrantly run timeouts
        timeout->mFiringId = firingId;

        numTimersToRun += 1;

        // Run only a limited number of timers based on the configured maximum.
        if (numTimersToRun % kNumTimersPerInitialElapsedCheck == 0) {
          now = TimeStamp::Now();
          TimeDuration elapsed(now - start);
          if (elapsed >= initialTimeLimit) {
            nextDeadline = timeout->When();
            break;
          }
        }
      }

//.........这里部分代码省略.........