StreamInserter.hpp

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// The Reactive C++ Toolbox.
// Copyright (C) 2022 Reactive Markets Limited
//
// Licensed 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.
 
#ifndef TOOLBOX_UTIL_STREAMINSERTER_HPP
#define TOOLBOX_UTIL_STREAMINSERTER_HPP
 
#include <utility>
 
namespace toolbox {
inline namespace util {
 
// clang-format off
template <typename OStreamT, typename FnT>
requires std::invocable<FnT, OStreamT&>
// clang-format on
class StreamInserter {
    friend OStreamT& operator<<(OStreamT& os, const StreamInserter& si)
    {
        si.fn_(os);
        return os;
    }
 
  public:
    explicit StreamInserter(FnT fn)
    : fn_{std::move(fn)}
    {
    }
    ~StreamInserter() = default;
 
    // Copy.
    StreamInserter(const StreamInserter&) = delete;
    StreamInserter& operator=(const StreamInserter&) = delete;
 
    // Move.
    StreamInserter(StreamInserter&&) noexcept = default;
    StreamInserter& operator=(StreamInserter&&) noexcept = delete;
 
  private:
    FnT fn_;
};
 
template <typename OStreamT, typename FnT>
auto make_stream_inserter(FnT fn)
{
    return StreamInserter<OStreamT, FnT>{std::move(fn)};
}
 
} // namespace util
} // namespace toolbox
 
#endif // TOOLBOX_UTIL_STREAMINSERTER_HPP