src/common/ityp_array.h

// Copyright 2020 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef COMMON_ITYP_ARRAY_H_
#define COMMON_ITYP_ARRAY_H_

#include "common/TypedInteger.h"
#include "common/UnderlyingType.h"

#include <array>
#include <cstddef>
#include <type_traits>

namespace ityp {

    // ityp::array is a helper class that wraps std::array with the restriction that
    // indices must be a particular type |Index|. Dawn uses multiple flat maps of
    // index-->data, and this class helps ensure an indices cannot be passed interchangably
    // to a flat map of a different type.
    template <typename Index, typename Value, size_t Size>
    class array : private std::array<Value, Size> {
        using I = UnderlyingType<Index>;
        using Base = std::array<Value, Size>;

        static_assert(Size <= std::numeric_limits<I>::max(), "");

      public:
        constexpr array() = default;

        template <typename... Values>
        constexpr array(Values&&... values) : Base{std::forward<Values>(values)...} {
        }

        Value& operator[](Index i) {
            I index = static_cast<I>(i);
            ASSERT(index >= 0 && index < I(Size));
            return Base::operator[](index);
        }

        constexpr const Value& operator[](Index i) const {
            I index = static_cast<I>(i);
            ASSERT(index >= 0 && index < I(Size));
            return Base::operator[](index);
        }

        Value& at(Index i) {
            I index = static_cast<I>(i);
            ASSERT(index >= 0 && index < I(Size));
            return Base::at(index);
        }

        constexpr const Value& at(Index i) const {
            I index = static_cast<I>(i);
            ASSERT(index >= 0 && index < I(Size));
            return Base::at(index);
        }

        typename Base::iterator begin() noexcept {
            return Base::begin();
        }

        typename Base::const_iterator begin() const noexcept {
            return Base::begin();
        }

        typename Base::iterator end() noexcept {
            return Base::end();
        }

        typename Base::const_iterator end() const noexcept {
            return Base::end();
        }

        constexpr Index size() const {
            return Index(I(Size));
        }

        using Base::back;
        using Base::data;
        using Base::empty;
        using Base::fill;
        using Base::front;
    };

}  // namespace ityp

#endif  // COMMON_ITYP_ARRAY_H_