src/tint/utils/containers/reverse.h

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#ifndef SRC_TINT_UTILS_CONTAINERS_REVERSE_H_
#define SRC_TINT_UTILS_CONTAINERS_REVERSE_H_

#include <iterator>

namespace tint {

namespace detail {
/// Used by tint::Reverse to hold the underlying iterable.
/// begin(ReverseIterable<T>) and end(ReverseIterable<T>) are automatically
/// called for range-for loops, via argument-dependent lookup.
/// See https://en.cppreference.com/w/cpp/language/range-for
template <typename T>
struct ReverseIterable {
    /// The wrapped iterable object.
    T& iterable;
};

template <typename T>
auto begin(ReverseIterable<T> r_it) {
    return std::rbegin(r_it.iterable);
}

template <typename T>
auto end(ReverseIterable<T> r_it) {
    return std::rend(r_it.iterable);
}
}  // namespace detail

/// Reverse returns an iterable wrapper that when used in range-for loops,
/// performs a reverse iteration over the object `iterable`.
/// Example:
/// ```
/// /* Equivalent to:
///  * for (auto it = vec.rbegin(); i != vec.rend(); ++it) {
///  *   auto v = *it;
///  */
/// for (auto v : tint::Reverse(vec)) {
/// }
/// ```
/// @param iterable the object to iterate
/// @returns the reverse iterable object
template <typename T>
detail::ReverseIterable<T> Reverse(T&& iterable) {
    return {iterable};
}

}  // namespace tint

#endif  // SRC_TINT_UTILS_CONTAINERS_REVERSE_H_