src/connectivity/bluetooth/lib/cpp-type/to_std_array.h

// Copyright 2020 The Fuchsia 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 SRC_CONNECTIVITY_BLUETOOTH_LIB_CPP_TYPE_TO_STD_ARRAY_H_
#define SRC_CONNECTIVITY_BLUETOOTH_LIB_CPP_TYPE_TO_STD_ARRAY_H_

#include <array>
#include <cstddef>
#include <type_traits>

namespace bt_lib_cpp_type {

// For object type T, provide a member |type| = T if T is not an array, otherwise |type| =
// std::array of elements of T (recursively if T is a multidimensional array).
// cv-qualifiers are retained.
template <typename T, typename Enable = void>
struct ToStdArray;  // undefined base case for references, zero length arrays, etc.

template <typename T>
struct ToStdArray<T, std::enable_if_t<std::is_object_v<T> && !std::is_array_v<T>>> {
  using type = T;
};

// Note that this specialization doesn't accept zero-length arrays, i.e. T[0].
template <typename T, size_t N>
struct ToStdArray<T[N]> {
  using type = std::array<typename ToStdArray<T>::type, N>;
};

// This accepts array function parameters and flexible array struct members, but not pointers.
template <typename T>
struct ToStdArray<T[]> {
  using type = std::array<typename ToStdArray<T>::type, 0>;
};

template <typename T>
using ToStdArrayT = typename ToStdArray<T>::type;

}  // namespace bt_lib_cpp_type

#endif  // SRC_CONNECTIVITY_BLUETOOTH_LIB_CPP_TYPE_TO_STD_ARRAY_H_