src/dawn/common/Range.h

// Copyright 2023 The Dawn & Tint Authors
//
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#ifndef SRC_DAWN_COMMON_RANGE_H_
#define SRC_DAWN_COMMON_RANGE_H_

#include <type_traits>
#include <utility>

namespace dawn {

// An iterator over a range of numbers. Simplified version of Python's range() iterator that works
// with any integer type (including ityp).
//
// Iterates over [0, end) in order:
//
//   for (auto i : Range(end)) { ... }
//
// Iterates over [start, end) in order:
//
//   for (auto i = Range(start, end)) { ... }
template <typename Integer>
class BeginEndRange {
  public:
    BeginEndRange(Integer begin, Integer end) : mBegin(begin), mEnd(end) {}

    class Iterator final {
      public:
        explicit Iterator(Integer value) : mValue(value) {}
        bool operator==(const Iterator& other) const { return other.mValue == mValue; }
        bool operator!=(const Iterator& other) const { return !(*this == other); }
        Iterator& operator++() {
            mValue++;
            return *this;
        }
        Integer operator*() const { return mValue; }

      private:
        Integer mValue;
    };

    Iterator begin() const { return Iterator(mBegin); }
    Iterator end() const { return Iterator(mEnd); }

  private:
    Integer mBegin;
    Integer mEnd;
};

template <typename Integer>
BeginEndRange<Integer> Range(Integer end) {
    return {Integer{}, end};
}
template <typename Integer>
BeginEndRange<Integer> Range(Integer begin, Integer end) {
    return {begin, end};
}

}  // namespace dawn

#endif  // SRC_DAWN_COMMON_RANGE_H_