arrow/util/type_traits.h

0001 // Licensed to the Apache Software Foundation (ASF) under one
0002 // or more contributor license agreements.  See the NOTICE file
0003 // distributed with this work for additional information
0004 // regarding copyright ownership.  The ASF licenses this file
0005 // to you under the Apache License, Version 2.0 (the
0006 // "License"); you may not use this file except in compliance
0007 // with the License.  You may obtain a copy of the License at
0008 //
0009 //   http://www.apache.org/licenses/LICENSE-2.0
0010 //
0011 // Unless required by applicable law or agreed to in writing,
0012 // software distributed under the License is distributed on an
0013 // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
0014 // KIND, either express or implied.  See the License for the
0015 // specific language governing permissions and limitations
0016 // under the License.
0017
0018 #pragma once
0019
0020 #include <cstdint>
0021 #include <type_traits>
0022
0023 namespace arrow {
0024 namespace internal {
0025
0026 /// \brief Metafunction to allow checking if a type matches any of another set of types
0027 template <typename...>
0028 struct IsOneOf : std::false_type {};  /// Base case: nothing has matched
0029
0030 template <typename T, typename U, typename... Args>
0031 struct IsOneOf<T, U, Args...> {
0032   /// Recursive case: T == U or T matches any other types provided (not including U).
0033   static constexpr bool value = std::is_same<T, U>::value || IsOneOf<T, Args...>::value;
0034 };
0035
0036 /// \brief Shorthand for using IsOneOf + std::enable_if
0037 template <typename T, typename... Args>
0038 using EnableIfIsOneOf = typename std::enable_if<IsOneOf<T, Args...>::value, T>::type;
0039
0040 /// \brief is_null_pointer from C++17
0041 template <typename T>
0042 struct is_null_pointer : std::is_same<std::nullptr_t, typename std::remove_cv<T>::type> {
0043 };
0044
0045 }  // namespace internal
0046 }  // namespace arrow