base/cxx17_backports.h

// Copyright 2021 The Chromium Authors
// 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 "polyfills/base/check.h"

namespace gurl_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 GURL_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) {
  GURL_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 gurl_base::clamp(v, lo, hi, std::less<T>{});
}

}  // namespace base

#endif  // BASE_CXX17_BACKPORTS_H_