1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556 |
- // Copyright 2021 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #ifndef BASE_CXX17_BACKPORTS_H_
- #define BASE_CXX17_BACKPORTS_H_
- #include <functional>
- #include <tuple>
- #include <type_traits>
- #include <utility>
- #include "base/check.h"
- #include "base/functional/invoke.h"
- namespace base {
- // C++14 implementation of C++17's std::clamp():
- // https://en.cppreference.com/w/cpp/algorithm/clamp
- // Please note that the C++ spec makes it undefined behavior to call std::clamp
- // with a value of `lo` that compares greater than the value of `hi`. This
- // implementation uses a CHECK to enforce this as a hard restriction.
- template <typename T, typename Compare>
- constexpr const T& clamp(const T& v, const T& lo, const T& hi, Compare comp) {
- CHECK(!comp(hi, lo));
- return comp(v, lo) ? lo : comp(hi, v) ? hi : v;
- }
- template <typename T>
- constexpr const T& clamp(const T& v, const T& lo, const T& hi) {
- return base::clamp(v, lo, hi, std::less<T>{});
- }
- // C++14 implementation of C++17's std::apply():
- // https://en.cppreference.com/w/cpp/utility/apply
- namespace internal {
- template <class F, class Tuple, std::size_t... I>
- constexpr decltype(auto) apply_impl(F&& f,
- Tuple&& t,
- std::index_sequence<I...>) {
- return base::invoke(std::forward<F>(f),
- std::get<I>(std::forward<Tuple>(t))...);
- }
- } // namespace internal
- template <class F, class Tuple>
- constexpr decltype(auto) apply(F&& f, Tuple&& t) {
- return internal::apply_impl(
- std::forward<F>(f), std::forward<Tuple>(t),
- std::make_index_sequence<
- std::tuple_size<std::remove_reference_t<Tuple>>::value>{});
- }
- } // namespace base
- #endif // BASE_CXX17_BACKPORTS_H_
|