mfbt/Opaque.h
author Nicholas Nethercote <nnethercote@mozilla.com>
Wed, 09 Aug 2017 20:41:38 +1000
changeset 427564 14de940bb317a497f50f6e80a1b5439fe9d049a6
parent 329986 967dcb05f34702b5fdbc12892c3f92d67fc3450a
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1386103 (part 1, attempt 3) - Specify nsAuto[C]String storage size via template parameter. r=dbaron.

/* -*- 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/. */

/* An opaque integral type supporting only comparison operators. */

#ifndef mozilla_Opaque_h
#define mozilla_Opaque_h

#include "mozilla/TypeTraits.h"

namespace mozilla {

/**
 * Opaque<T> is a replacement for integral T in cases where only comparisons
 * must be supported, and it's desirable to prevent accidental dependency on
 * exact values.
 */
template<typename T>
class Opaque final
{
  static_assert(mozilla::IsIntegral<T>::value,
                "mozilla::Opaque only supports integral types");

  T mValue;

public:
  Opaque() {}
  explicit Opaque(T aValue) : mValue(aValue) {}

  bool operator==(const Opaque& aOther) const {
    return mValue == aOther.mValue;
  }

  bool operator!=(const Opaque& aOther) const {
    return !(*this == aOther);
  }
};

} // namespace mozilla

#endif /* mozilla_Opaque_h */