/* -*- 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 "nsMemoryPressure.h"

#include "mozilla/Assertions.h"

#include "mozilla/Atomics.h"

#include "nsThreadUtils.h"

using namespace mozilla;

static Atomic<int32_t, Relaxed> sMemoryPressurePending;

static_assert(MemPressure_None == 0,

              "Bad static initialization with the default constructor.");

MemoryPressureState

NS_GetPendingMemoryPressure()

{

  int32_t value = sMemoryPressurePending.exchange(MemPressure_None);

  return MemoryPressureState(value);

}

void

NS_DispatchEventualMemoryPressure(MemoryPressureState aState)

{

  /*

   * A new memory pressure event erases an ongoing (or stop of) memory pressure,

   * but an existing "new" memory pressure event takes precedence over a new

   * "ongoing" or "stop" memory pressure event.

   */

  switch (aState) {

    case MemPressure_None:

      sMemoryPressurePending = MemPressure_None;

      break;

    case MemPressure_New:

      sMemoryPressurePending = MemPressure_New;

      break;

    case MemPressure_Ongoing:

    case MemPressure_Stopping:

      sMemoryPressurePending.compareExchange(MemPressure_None,

                                             aState);

      break;

  }

}

nsresult

NS_DispatchMemoryPressure(MemoryPressureState aState)

{

  NS_DispatchEventualMemoryPressure(aState);

  nsCOMPtr<nsIRunnable> event = new Runnable("NS_DispatchEventualMemoryPressure");

  return NS_DispatchToMainThread(event);

}