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// Copyright 2021 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
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//
// 3. Neither the name of the copyright holder nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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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_