gecko/dom/workers/Performance.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "Performance.h"
#include "mozilla/dom/PerformanceBinding.h"

#include "WorkerPrivate.h"

BEGIN_WORKERS_NAMESPACE

Performance::Performance(WorkerPrivate* aWorkerPrivate)
  : mWorkerPrivate(aWorkerPrivate)
{
  mWorkerPrivate->AssertIsOnWorkerThread();
}

Performance::~Performance()
{
  mWorkerPrivate->AssertIsOnWorkerThread();
}

JSObject*
Performance::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
{
  return PerformanceBinding_workers::Wrap(aCx, this, aGivenProto);
}

DOMHighResTimeStamp
Performance::Now() const
{
  TimeDuration duration =
    TimeStamp::Now() - mWorkerPrivate->NowBaseTimeStamp();
  double nowTime = duration.ToMilliseconds();
  // Round down to the nearest 5us, because if the timer is too accurate people
  // can do nasty timing attacks with it.  See similar code in the non-worker
  // Performance implementation.
  const double maxResolutionMs = 0.005;
  return floor(nowTime / maxResolutionMs) * maxResolutionMs;
}

// To be removed once bug 1124165 lands
bool
Performance::IsPerformanceTimingAttribute(const nsAString& aName)
{
  // In workers we just support navigationStart.
  return aName.EqualsASCII("navigationStart");
}

DOMHighResTimeStamp
Performance::GetPerformanceTimingFromString(const nsAString& aProperty)
{
  if (!IsPerformanceTimingAttribute(aProperty)) {
    return 0;
  }

  if (aProperty.EqualsLiteral("navigationStart")) {
    return mWorkerPrivate->NowBaseTimeHighRes();
  }

  MOZ_CRASH("IsPerformanceTimingAttribute and GetPerformanceTimingFromString are out of sync");
  return 0;
}

DOMHighResTimeStamp
Performance::DeltaFromNavigationStart(DOMHighResTimeStamp aTime)
{
  if (aTime == 0) {
    return 0;
  }

  return aTime - mWorkerPrivate->NowBaseTimeHighRes();
}

void
Performance::DispatchBufferFullEvent()
{
  // This method is needed just for InsertResourceEntry, but this method is not
  // exposed to workers.
  MOZ_CRASH("This should not be called.");
}

END_WORKERS_NAMESPACE