src/dawn/native/EnumMaskIterator.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 DAWNNATIVE_ENUMMASKITERATOR_H_
#define DAWNNATIVE_ENUMMASKITERATOR_H_

#include "dawn/common/BitSetIterator.h"
#include "dawn/native/EnumClassBitmasks.h"

namespace dawn::native {

    template <typename T>
    class EnumMaskIterator final {
        static constexpr size_t N = EnumBitmaskSize<T>::value;
        static_assert(N > 0);

        using U = std::underlying_type_t<T>;

      public:
        EnumMaskIterator(const T& mask) : mBitSetIterator(std::bitset<N>(static_cast<U>(mask))) {
            // If you hit this ASSERT it means that you forgot to update EnumBitmaskSize<T>::value;
            ASSERT(U(mask) == 0 || Log2(uint64_t(U(mask))) < N);
        }

        class Iterator final {
          public:
            Iterator(const typename BitSetIterator<N, U>::Iterator& iter) : mIter(iter) {
            }

            Iterator& operator++() {
                ++mIter;
                return *this;
            }

            bool operator==(const Iterator& other) const {
                return mIter == other.mIter;
            }

            bool operator!=(const Iterator& other) const {
                return mIter != other.mIter;
            }

            T operator*() const {
                U value = *mIter;
                return static_cast<T>(U(1) << value);
            }

          private:
            typename BitSetIterator<N, U>::Iterator mIter;
        };

        Iterator begin() const {
            return Iterator(mBitSetIterator.begin());
        }

        Iterator end() const {
            return Iterator(mBitSetIterator.end());
        }

      private:
        BitSetIterator<N, U> mBitSetIterator;
    };

    template <typename T>
    EnumMaskIterator<T> IterateEnumMask(const T& mask) {
        return EnumMaskIterator<T>(mask);
    }

}  // namespace dawn::native

#endif  // DAWNNATIVE_ENUMMASKITERATOR_H_