// 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 #pragma once #include #include #include #include #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 sstream_; std::ostream& ostream_; }; } // namespace detail template void StringBuilderRecursive(std::ostream& stream, Head&& head) { stream << head; } template void StringBuilderRecursive(std::ostream& stream, Head&& head, Tail&&... tail) { StringBuilderRecursive(stream, std::forward(head)); StringBuilderRecursive(stream, std::forward(tail)...); } template std::string StringBuilder(Args&&... args) { detail::StringStreamWrapper ss; StringBuilderRecursive(ss.stream(), std::forward(args)...); return ss.str(); } /// CRTP helper for declaring string representation. Defines operator<< template class ToStringOstreamable { public: ~ToStringOstreamable() { static_assert( std::is_same().ToString()), std::string>::value, "ToStringOstreamable depends on the method T::ToString() const"); } private: const T& cast() const { return static_cast(*this); } friend inline std::ostream& operator<<(std::ostream& os, const ToStringOstreamable& t) { return os << t.cast().ToString(); } }; } // namespace util } // namespace arrow