class to delegate file output file actions

src/OutputFileHandler.h

+#ifndef OUTPUTFILEHANDLER_H
+#define OUTPUTFILEHANDLER_H
+
+#include <cstdint>
+#include <cstdio>
+#include <string>
+
+class OutputFileHandler {
+ public:
+  OutputFileHandler(const std::string filename_base_path, const std::string filename_prefix)
+      : filename_base_path_(filename_base_path),
+        filename_prefix_(filename_prefix),
+        working_files_basepath_(filename_base_path_ + "/" + working_dir_) {
+    create_output_directory_maybe(working_files_basepath_);
+  }
+  virtual ~OutputFileHandler() {}
+
+  void open_file(uint32_t index,
+                 uint32_t run);  // Used for fixedNorbits per file option
+  {
+    // Create a new file
+    std::string output_directory = my_output_filename_base + "/" + working_dir;
+    create_output_directory(output_directory);
+    std::string current_filename_a =
+        output_directory + "/" +
+        format_run_file_stem(my_output_filename_prefix, current_run_number, index_);
+    std::string filename =
+        output_directory + "/" +
+        format_run_file_stem(my_output_filename_prefix, control.run_number, index_);
+    LOG(INFO) << "opening file with index " << index_;
+    outFile.setFile(fopen(filename.c_str(), "w"));
+    outFile.setIndex(index_);
+    if (outFile.getFile() == NULL) {
+      std::string err = tools::strerror("ERROR when creating file '" + current_filename_a + "'");
+      LOG(ERROR) << err;
+      throw std::runtime_error(err);
+    }
+  }
+
+ private:
+  void create_output_directory_maybe(std::string &output_directory);
+
+  // name of subdir where the files are stored before they are moved to the
+  // final destination
+  static constexpr std::string working_dir_{"in_progress"};
+  // name of the journal file. Note: Filename prefix is added making the final
+  // filename
+  static constexpr std::string journal_file_{"index.journal"};
+
+  std::string filename_base_path_;
+  std::string filename_prefix_;
+  std::string working_files_basepath_;
+  uint32_t current_run_number_;
+  FILE *current_file_;
+  int32_t current_index_;
+};
+#endif