gecko-dev/mfbt/Array.h

/* -*- 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/. */

/* A compile-time constant-length array with bounds-checking assertions. */

#ifndef mozilla_Array_h
#define mozilla_Array_h

#include <stddef.h>

#include <iterator>
#include <ostream>
#include <utility>

#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/Likely.h"

namespace mozilla {

template <typename T, size_t _Length>
class Array {
  T mArr[_Length];

 public:
  using ElementType = T;
  static constexpr size_t Length = _Length;

  constexpr Array() = default;

  template <typename... Args>
  MOZ_IMPLICIT constexpr Array(Args&&... aArgs)
      : mArr{std::forward<Args>(aArgs)...} {
    static_assert(sizeof...(aArgs) == Length,
                  "The number of arguments should be equal to the template "
                  "parameter Length");
  }

  constexpr T& operator[](size_t aIndex) {
    if (MOZ_UNLIKELY(aIndex >= Length)) {
      detail::InvalidArrayIndex_CRASH(aIndex, Length);
    }
    return mArr[aIndex];
  }

  constexpr const T& operator[](size_t aIndex) const {
    if (MOZ_UNLIKELY(aIndex >= Length)) {
      detail::InvalidArrayIndex_CRASH(aIndex, Length);
    }
    return mArr[aIndex];
  }

  bool operator==(const Array<T, Length>& aOther) const {
    for (size_t i = 0; i < Length; i++) {
      if (mArr[i] != aOther[i]) {
        return false;
      }
    }
    return true;
  }

  typedef T* iterator;
  typedef const T* const_iterator;
  typedef std::reverse_iterator<T*> reverse_iterator;
  typedef std::reverse_iterator<const T*> const_reverse_iterator;

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

  // Method for std::size.
  constexpr size_t size() const { return Length; }

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

template <typename T>
class Array<T, 0> {
 public:
  T& operator[](size_t aIndex) { MOZ_CRASH("indexing into zero-length array"); }

  const T& operator[](size_t aIndex) const {
    MOZ_CRASH("indexing into zero-length array");
  }
};

// MOZ_DBG support

template <typename T, size_t Length>
std::ostream& operator<<(std::ostream& aOut, const Array<T, Length>& aArray) {
  return aOut << Span(aArray);
}

} /* namespace mozilla */

#endif /* mozilla_Array_h */