65 lines
1.8 KiB
C++
65 lines
1.8 KiB
C++
// Copyright 2021 The Tint Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SRC_TINT_UTILS_REVERSE_H_
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#define SRC_TINT_UTILS_REVERSE_H_
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#include <iterator>
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namespace tint {
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namespace utils {
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namespace detail {
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/// Used by utils::Reverse to hold the underlying iterable.
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/// begin(ReverseIterable<T>) and end(ReverseIterable<T>) are automatically
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/// called for range-for loops, via argument-dependent lookup.
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/// See https://en.cppreference.com/w/cpp/language/range-for
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template <typename T>
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struct ReverseIterable {
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/// The wrapped iterable object.
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T& iterable;
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};
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template <typename T>
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auto begin(ReverseIterable<T> r_it) {
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return std::rbegin(r_it.iterable);
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}
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template <typename T>
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auto end(ReverseIterable<T> r_it) {
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return std::rend(r_it.iterable);
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}
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} // namespace detail
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/// Reverse returns an iterable wrapper that when used in range-for loops,
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/// performs a reverse iteration over the object `iterable`.
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/// Example:
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/// ```
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/// /* Equivalent to:
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/// * for (auto it = vec.rbegin(); i != vec.rend(); ++it) {
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/// * auto v = *it;
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/// */
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/// for (auto v : utils::Reverse(vec)) {
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/// }
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/// ```
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template <typename T>
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detail::ReverseIterable<T> Reverse(T&& iterable) {
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return {iterable};
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}
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} // namespace utils
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} // namespace tint
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#endif // SRC_TINT_UTILS_REVERSE_H_
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