// 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 <type_traits>
#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) {
if constexpr (std::is_floating_point_v<std::decay_t<Head>>) {
// Avoid losing precision when printing floating point numbers
stream << std::to_string(head);
} else {
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