stdout_redirector.hpp

Go to the documentation of this file.

/*
Copyright (c) 2025 acrion innovations GmbH
Authors: Stefan Zipproth, s.zipproth@acrion.ch
 
This file is part of Cbeam, see https://github.com/acrion/cbeam and https://cbeam.org
 
Cbeam is offered under a commercial and under the AGPL license.
For commercial licensing, contact us at https://acrion.ch/sales. For AGPL licensing, see below.
 
AGPL licensing:
 
Cbeam is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
 
Cbeam is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
 
You should have received a copy of the GNU Affero General Public License
along with Cbeam. If not, see <https://www.gnu.org/licenses/>.
*/
 
#pragma once
 
#include <cbeam/error/runtime_error.hpp> // for cbeam::error:runtime_error
#include <cbeam/logging/log_manager.hpp> // for CBEAM_LOG_DEBUG
 
#include <cassert> // for assert
#include <cstdio>  // for freopen, fclose, stdout
 
#include <filesystem> // for std::filesystem::path
#include <mutex>      // for std::mutex, std::lock_guard
#include <string>     // for std::operator+
 
#ifdef _WIN32
    #include <cbeam/platform/windows_config.hpp>
    #include <io.h>
#endif
 
namespace cbeam::filesystem
{
    class stdout_redirector
    {
    public:
        explicit stdout_redirector(const std::filesystem::path& file_path)
        {
            std::lock_guard<std::mutex> lock(_mtx);
            if (freopen(file_path.string().c_str(), "w", stdout) == nullptr)
            {
                throw cbeam::error::runtime_error("cbeam::filesystem::stdout_redirector: Could not redirect stdout to file " + file_path.string());
            }
        }

        virtual ~stdout_redirector() noexcept
        {
            try
            {
                std::lock_guard<std::mutex> lock(_mtx);
                auto                        redirected_stdout = stdout;
                fflush(stdout);
                bool done = false;
#ifdef _WIN32
                HANDLE hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
                if (hStdout != INVALID_HANDLE_VALUE)
                {
                    int fdStdout = _open_osfhandle((intptr_t)hStdout, _O_TEXT);
                    if (fdStdout != -1)
                    {
                        FILE* fpStdout = _fdopen(fdStdout, "w");
                        if (fpStdout)
                        {
                            *stdout = *fpStdout;
                            std::setvbuf(stdout, NULL, _IONBF, 0);
                        }
                        else
                        {
                            CBEAM_LOG("cbeam::filesystem::stdout_redirector: Could not set stdout to default (failed to reopen stdout as FILE*)");
                        }
                    }
                    else
                    {
                        CBEAM_LOG("cbeam::filesystem::stdout_redirector: Could not set stdout to default (failed to open osfhandle as file descriptor)");
                    }
                }
                else
                {
                    CBEAM_LOG("cbeam::filesystem::stdout_redirector: Could not set stdout to default (invalid standard output handle)");
                }
#else
                done = freopen("/dev/tty", "w", stdout) != nullptr;
 
                if (!done)
                {
                    CBEAM_LOG("cbeam::filesystem::stdout_redirector: Could not set stdout to default");
                }
#endif
                if (done && redirected_stdout != stdout)
                {
                    assert(fclose(redirected_stdout) == 0);
                }
            }
            catch (const std::system_error& ex)
            {
                CBEAM_LOG("cbeam::filesystem::stdout_redirector: Could not lock the mutex. This indicates a serious (unexpected) bug that must be fixed during development phase.");
                assert(false);
            }
        }
 
    private:
        std::mutex _mtx;
    };
}