| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License. template <typename T> |
| |
| #pragma once |
| |
| #include <memory> |
| #include <ostream> |
| #include <string> |
| #include <utility> |
| |
| #include "arrow/util/visibility.h" |
| |
| namespace arrow { |
| namespace util { |
| |
| namespace detail { |
| |
| class ARROW_EXPORT StringStreamWrapper { |
| public: |
| StringStreamWrapper(); |
| ~StringStreamWrapper(); |
| |
| std::ostream& stream() { return ostream_; } |
| std::string str(); |
| |
| protected: |
| std::unique_ptr<std::ostringstream> sstream_; |
| std::ostream& ostream_; |
| }; |
| |
| } // namespace detail |
| |
| template <typename Head> |
| void StringBuilderRecursive(std::ostream& stream, Head&& head) { |
| stream << head; |
| } |
| |
| template <typename Head, typename... Tail> |
| void StringBuilderRecursive(std::ostream& stream, Head&& head, Tail&&... tail) { |
| StringBuilderRecursive(stream, std::forward<Head>(head)); |
| StringBuilderRecursive(stream, std::forward<Tail>(tail)...); |
| } |
| |
| template <typename... Args> |
| std::string StringBuilder(Args&&... args) { |
| detail::StringStreamWrapper ss; |
| StringBuilderRecursive(ss.stream(), std::forward<Args>(args)...); |
| return ss.str(); |
| } |
| |
| /// CRTP helper for declaring string representation. Defines operator<< |
| template <typename T> |
| class ToStringOstreamable { |
| public: |
| ~ToStringOstreamable() { |
| static_assert( |
| std::is_same<decltype(std::declval<const T>().ToString()), std::string>::value, |
| "ToStringOstreamable depends on the method T::ToString() const"); |
| } |
| |
| private: |
| const T& cast() const { return static_cast<const T&>(*this); } |
| |
| friend inline std::ostream& operator<<(std::ostream& os, const ToStringOstreamable& t) { |
| return os << t.cast().ToString(); |
| } |
| }; |
| |
| } // namespace util |
| } // namespace arrow |
