Catch2/src/catch2/internal/catch_reusable_string_stream.cpp

//              Copyright Catch2 Authors
// Distributed under the Boost Software License, Version 1.0.
//   (See accompanying file LICENSE_1_0.txt or copy at
//        https://www.boost.org/LICENSE_1_0.txt)

// SPDX-License-Identifier: BSL-1.0
#include <catch2/internal/catch_reusable_string_stream.hpp>
#include <catch2/internal/catch_singletons.hpp>
#include <catch2/internal/catch_unique_ptr.hpp>

#include <cstdio>
#include <sstream>
#include <vector>

namespace Catch {

    // This class encapsulates the idea of a pool of ostringstreams that can be reused.
    struct StringStreams {
        std::vector<Detail::unique_ptr<std::ostringstream>> m_streams;
        std::vector<std::size_t> m_unused;
        std::ostringstream m_referenceStream; // Used for copy state/ flags from

        auto add() -> std::size_t {
            if( m_unused.empty() ) {
                m_streams.push_back( Detail::make_unique<std::ostringstream>() );
                return m_streams.size()-1;
            }
            else {
                auto index = m_unused.back();
                m_unused.pop_back();
                return index;
            }
        }

        void release( std::size_t index ) {
            m_streams[index]->copyfmt( m_referenceStream ); // Restore initial flags and other state
            m_unused.push_back(index);
        }
    };

    ReusableStringStream::ReusableStringStream()
    :   m_index( Singleton<StringStreams>::getMutable().add() ),
        m_oss( Singleton<StringStreams>::getMutable().m_streams[m_index].get() )
    {}

    ReusableStringStream::~ReusableStringStream() {
        static_cast<std::ostringstream*>( m_oss )->str("");
        m_oss->clear();
        Singleton<StringStreams>::getMutable().release( m_index );
    }

    std::string ReusableStringStream::str() const {
        return static_cast<std::ostringstream*>( m_oss )->str();
    }

    void ReusableStringStream::str( std::string const& str ) {
        static_cast<std::ostringstream*>( m_oss )->str( str );
    }


}