mfbt/EnumeratedArray.h
author Narcis Beleuzu <nbeleuzu@mozilla.com>
Thu, 21 Jun 2018 16:51:55 +0300
changeset 477502 59322b179c0fdb4423d42b624da7bf64ee5a2327
parent 475188 bb85c5ee5afc151be0d07ecc48318dc69cfef446
child 502575 79148f9b36487274b734e30b48a18608e250cc99
permissions -rw-r--r--
Backed out 4 changesets (bug 1268889) for Windows GTest failures. CLOSED TREE Backed out changeset da427a67372e (bug 1268889) Backed out changeset 97528847b7b7 (bug 1268889) Backed out changeset b2320061fbcb (bug 1268889) Backed out changeset dd3b7047ea6f (bug 1268889)

/* -*- 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/. */

/* EnumeratedArray is like Array, but indexed by a typed enum. */

#ifndef mozilla_EnumeratedArray_h
#define mozilla_EnumeratedArray_h

#include "mozilla/Array.h"
#include "mozilla/Move.h"

namespace mozilla {

/**
 * EnumeratedArray is a fixed-size array container for use when an
 * array is indexed by a specific enum class.
 *
 * This provides type safety by guarding at compile time against accidentally
 * indexing such arrays with unrelated values. This also removes the need
 * for manual casting when using a typed enum value to index arrays.
 *
 * Aside from the typing of indices, EnumeratedArray is similar to Array.
 *
 * Example:
 *
 *   enum class AnimalSpecies {
 *     Cow,
 *     Sheep,
 *     Count
 *   };
 *
 *   EnumeratedArray<AnimalSpecies, AnimalSpecies::Count, int> headCount;
 *
 *   headCount[AnimalSpecies::Cow] = 17;
 *   headCount[AnimalSpecies::Sheep] = 30;
 *
 */
template<typename IndexType,
         IndexType SizeAsEnumValue,
         typename ValueType>
class EnumeratedArray
{
public:
  static const size_t kSize = size_t(SizeAsEnumValue);

private:
  typedef Array<ValueType, kSize> ArrayType;

  ArrayType mArray;

public:
  EnumeratedArray() {}

  template <typename... Args>
  MOZ_IMPLICIT EnumeratedArray(Args&&... aArgs)
    : mArray{std::forward<Args>(aArgs)...}
  {}

  explicit EnumeratedArray(const EnumeratedArray& aOther)
  {
    for (size_t i = 0; i < kSize; i++) {
      mArray[i] = aOther.mArray[i];
    }
  }

  EnumeratedArray(EnumeratedArray&& aOther)
  {
    for (size_t i = 0; i < kSize; i++) {
      mArray[i] = std::move(aOther.mArray[i]);
    }
  }

  ValueType& operator[](IndexType aIndex)
  {
    return mArray[size_t(aIndex)];
  }

  const ValueType& operator[](IndexType aIndex) const
  {
    return mArray[size_t(aIndex)];
  }

  EnumeratedArray& operator =(EnumeratedArray&& aOther)
  {
    for (size_t i = 0; i < kSize; i++) {
      mArray[i] = std::move(aOther.mArray[i]);
    }
    return *this;
  }

  typedef typename ArrayType::iterator               iterator;
  typedef typename ArrayType::const_iterator         const_iterator;
  typedef typename ArrayType::reverse_iterator       reverse_iterator;
  typedef typename ArrayType::const_reverse_iterator const_reverse_iterator;

  // Methods for range-based for loops.
  iterator begin() { return mArray.begin(); }
  const_iterator begin() const { return mArray.begin(); }
  const_iterator cbegin() const { return mArray.cbegin(); }
  iterator end() { return mArray.end(); }
  const_iterator end() const { return mArray.end(); }
  const_iterator cend() const { return mArray.cend(); }

  // Methods for reverse iterating.
  reverse_iterator rbegin() { return mArray.rbegin(); }
  const_reverse_iterator rbegin() const { return mArray.rbegin(); }
  const_reverse_iterator crbegin() const { return mArray.crbegin(); }
  reverse_iterator rend() { return mArray.rend(); }
  const_reverse_iterator rend() const { return mArray.rend(); }
  const_reverse_iterator crend() const { return mArray.crend(); }
};

} // namespace mozilla

#endif // mozilla_EnumeratedArray_h