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// Copyright 2021 The Tint 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 SRC_TINT_UTILS_REVERSE_H_
#define SRC_TINT_UTILS_REVERSE_H_
#include <iterator>
namespace tint::utils {
namespace detail {
/// Used by utils::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 : utils::Reverse(vec)) {
/// }
/// ```
template <typename T>
detail::ReverseIterable<T> Reverse(T&& iterable) {
return {iterable};
}
} // namespace tint::utils
#endif // SRC_TINT_UTILS_REVERSE_H_