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/**
* Copyright (C) 2022-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <algorithm>
#include <functional>
namespace mongo {
/**
* Work-alike to C++20 constexpr std::is_sorted_until.
*
* Implementation from: https://en.cppreference.com/w/cpp/algorithm/is_sorted_until
*/
template <class ForwardIt, class Compare>
constexpr ForwardIt constexprIsSortedUntil(ForwardIt first, ForwardIt last, Compare comp) {
#if __cpp_lib_constexpr_algorithms >= 201806L
return std::is_sorted_until(first, last, comp);
#else
if (first != last) {
ForwardIt next = first;
while (++next != last) {
if (comp(*next, *first))
return next;
first = next;
}
}
return last;
#endif
}
/**
* Work-alike to C++20 constexpr std::is_sorted_until.
*/
template <typename ForwardIt>
constexpr bool constexprIsSortedUntil(ForwardIt first, ForwardIt last) {
return constexprIsSortedUntil(first, last, std::less<>{});
}
/**
* Work-alike to C++20 constexpr std::is_sorted.
*
* Implementation from: https://en.cppreference.com/w/cpp/algorithm/is_sorted
*/
template <typename ForwardIt, typename Compare>
constexpr bool constexprIsSorted(ForwardIt first, ForwardIt last, Compare comp) {
#if __cpp_lib_constexpr_algorithms >= 201806L
return std::is_sorted(first, last, comp);
#else
return constexprIsSortedUntil(first, last, comp) == last;
#endif
}
/**
* Work-alike to C++20 constexpr std::is_sorted.
*/
template <typename ForwardIt>
constexpr bool constexprIsSorted(ForwardIt first, ForwardIt last) {
return constexprIsSorted(first, last, std::less<>{});
}
} // namespace mongo
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