Update step logger

Fixed bugs with multithreading and added protection against data lost with insufficiently accurate setting of the maximum value of the file size

include/spdlog/contrib/sinks/step_file_sink.h

@@ -99,9 +99,12 @@ public:
         _file_helper.open(_current_filename);
         _current_size = _file_helper.size(); // expensive. called only once
 
+        if (!_current_size)
+        {
             _current_size += _file_header.formatted.size();
             if (_current_size) _file_helper.write(_file_header);
         }
+    }
 
     ~step_file_sink()
     {
@@ -123,14 +126,17 @@ protected:
         {
             filename_t new_filename;
             std::tie(new_filename, std::ignore) = FileNameCalc::calc_filename(_base_filename, _tmp_ext);
-            if (new_filename != _current_filename)
-            {
-                close_current_file();
             
-                // std::tie(_current_filename, std::ignore) = FileNameCalc::calc_filename(_base_filename, _tmp_ext);
+            bool change_occured = !details::file_helper::file_exists(new_filename);
+            if (change_occured) close_current_file();
+
+            _current_filename = std::move(new_filename);
+
             _file_helper.open(_current_filename);
             _tp = _next_tp();
 
+            if (change_occured)
+            {
                 _current_size = _file_header.formatted.size();
                 if (_current_size) _file_helper.write(_file_header);
             }