nsExpirationState.h

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/* -*- 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/. */

#ifndef nsExpirationState_h_

#define nsExpirationState_h_

#include <cstdint>

// Data used to track the expiration state of an object with nsExpirationTracker

struct nsExpirationState {

  enum {

    NOT_TRACKED = (1U << 4) - 1,

    MAX_INDEX_IN_GENERATION = (1U << 28) - 1

};

  constexpr nsExpirationState()

      : mGeneration(NOT_TRACKED), mIndexInGeneration(0) {}

  bool IsTracked() const { return mGeneration != NOT_TRACKED; }

  // The generation that this object belongs to, or NOT_TRACKED.

  uint32_t mGeneration : 4;

  uint32_t mIndexInGeneration : 28;

};

// We promise that this is 32 bits so that objects that includes this as a

// field can pad and align efficiently.

static_assert(sizeof(nsExpirationState) == sizeof(uint32_t));

#endif