third_party/base/cxx17_backports.h

// 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 THIRD_PARTY_BASE_CXX17_BACKPORTS_H_
#define THIRD_PARTY_BASE_CXX17_BACKPORTS_H_

#include <stddef.h>

#include <functional>

#include "third_party/base/check.h"

namespace pdfium {

// C++14 implementation of C++17's std::size():
// http://en.cppreference.com/w/cpp/iterator/size
template <typename Container>
constexpr auto size(const Container& c) -> decltype(c.size()) {
  return c.size();
}

template <typename T, size_t N>
constexpr size_t size(const T (&array)[N]) noexcept {
  return N;
}

// 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 pdfium::clamp(v, lo, hi, std::less<T>{});
}

}  // namespace pdfium

#endif  // THIRD_PARTY_BASE_CXX17_BACKPORTS_H_