src/dawn/native/EnumMaskIterator.h

// Copyright 2020 The Dawn & Tint Authors
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#ifndef SRC_DAWN_NATIVE_ENUMMASKITERATOR_H_
#define SRC_DAWN_NATIVE_ENUMMASKITERATOR_H_

#include "dawn/common/ityp_bitset.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:
    explicit EnumMaskIterator(const T& mask) : mBitSet(static_cast<U>(mask)) {
        // If you hit this DAWN_ASSERT it means that you forgot to update EnumBitmaskSize<T>::value;
        DAWN_ASSERT(U(mask) == 0 || Log2(uint64_t(U(mask))) < N);
    }

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

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

        bool operator==(const Iterator& other) const = default;

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

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

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

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

  private:
    ityp::bitset<U, N> mBitSet;
};

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

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_ENUMMASKITERATOR_H_