text: // Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
  // Distributed under the MIT License (http://opensource.org/licenses/MIT)
  
  #pragma once
  
  #include <spdlog/sinks/base_sink.h>
  #include <spdlog/details/file_helper.h>
  #include <spdlog/details/null_mutex.h>
  #include <spdlog/details/synchronous_factory.h>
  
  #include <chrono>
  #include <mutex>
  #include <string>
  
  namespace spdlog {
  namespace sinks {
  
  //
  // Rotating file sink based on size
  //
  template<typename Mutex>
  class rotating_file_sink final : public base_sink<Mutex>
  {
  public:
      rotating_file_sink(filename_t base_filename, std::size_t max_size, std::size_t max_files, bool rotate_on_open = false);
      static filename_t calc_filename(const filename_t &filename, std::size_t index);
      const filename_t &filename();
  
  protected:
      void sink_it_(const details::log_msg &msg) override;
      void flush_() override;
  
  private:
      // Rotate files:
      // log.txt -> log.1.txt
      // log.1.txt -> log.2.txt
      // log.2.txt -> log.3.txt
      // log.3.txt -> delete
      void rotate_();
  
      // delete the target if exists, and rename the src file  to target
      // return true on success, false otherwise.
      bool rename_file_(const filename_t &src_filename, const filename_t &target_filename);
  
      filename_t base_filename_;
      std::size_t max_size_;
      std::size_t max_files_;
      std::size_t current_size_;
      details::file_helper file_helper_;
  };
  
  using rotating_file_sink_mt = rotating_file_sink<std::mutex>;
  using rotating_file_sink_st = rotating_file_sink<details::null_mutex>;
  
  } // namespace sinks
  
  //
  // factory functions
  //
  
  template<typename Factory = spdlog::synchronous_factory>
  inline std::shared_ptr<logger> rotating_logger_mt(
      const std::string &logger_name, const filename_t &filename, size_t max_file_size, size_t max_files, bool rotate_on_open = false)
  {
      return Factory::template create<sinks::rotating_file_sink_mt>(logger_name, filename, max_file_size, max_files, rotate_on_open);
  }
  
  template<typename Factory = spdlog::synchronous_factory>
  inline std::shared_ptr<logger> rotating_logger_st(
      const std::string &logger_name, const filename_t &filename, size_t max_file_size, size_t max_files, bool rotate_on_open = false)
  {
      return Factory::template create<sinks::rotating_file_sink_st>(logger_name, filename, max_file_size, max_files, rotate_on_open);
  }
  } // namespace spdlog
  
  #ifdef SPDLOG_HEADER_ONLY
  #include "rotating_file_sink-inl.h"
  #endif
  