cef/include/base/cef_cxx17_backports.h

// Copyright (c) 2021 Marshall A. Greenblatt. Portions copyright (c) 2021
// Google Inc. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//    * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//    * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//    * Neither the name of Google Inc. nor the name Chromium Embedded
// Framework nor the names of its contributors may be used to endorse
// or promote products derived from this software without specific prior
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//

#ifndef CEF_INCLUDE_BASE_CEF_CXX17_BACKPORTS_H_
#define CEF_INCLUDE_BASE_CEF_CXX17_BACKPORTS_H_
#pragma once

#if defined(USING_CHROMIUM_INCLUDES)
// When building CEF include the Chromium header directly.
// TODO(cef): Change to "base/cxx17_backports.h" in M93.
#include "base/stl_util.h"
#else  // !USING_CHROMIUM_INCLUDES
// The following is substantially similar to the Chromium implementation.
// If the Chromium implementation diverges the below implementation should be
// updated to match.

#include <array>
#include <initializer_list>
#include <memory>
#include <string>

namespace base {

// 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::empty():
// http://en.cppreference.com/w/cpp/iterator/empty
template <typename Container>
constexpr auto empty(const Container& c) -> decltype(c.empty()) {
  return c.empty();
}

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

template <typename T>
constexpr bool empty(std::initializer_list<T> il) noexcept {
  return il.size() == 0;
}

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

// std::basic_string::data() had no mutable overload prior to C++17 [1].
// Hence this overload is provided.
// Note: str[0] is safe even for empty strings, as they are guaranteed to be
// null-terminated [2].
//
// [1] http://en.cppreference.com/w/cpp/string/basic_string/data
// [2] http://en.cppreference.com/w/cpp/string/basic_string/operator_at
template <typename CharT, typename Traits, typename Allocator>
CharT* data(std::basic_string<CharT, Traits, Allocator>& str) {
  return std::addressof(str[0]);
}

template <typename Container>
constexpr auto data(const Container& c) -> decltype(c.data()) {
  return c.data();
}

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

template <typename T>
constexpr const T* data(std::initializer_list<T> il) noexcept {
  return il.begin();
}

// std::array::data() was not constexpr prior to C++17 [1].
// Hence these overloads are provided.
//
// [1] https://en.cppreference.com/w/cpp/container/array/data
template <typename T, size_t N>
constexpr T* data(std::array<T, N>& array) noexcept {
  return !array.empty() ? &array[0] : nullptr;
}

template <typename T, size_t N>
constexpr const T* data(const std::array<T, N>& array) noexcept {
  return !array.empty() ? &array[0] : nullptr;
}

}  // namespace base

#endif  // !USING_CHROMIUM_INCLUDES

#endif  // CEF_INCLUDE_BASE_CEF_CXX17_BACKPORTS_H_