static long saveGZStructureToFile(S file, O o) {

  ret saveGZStructureToFile(getProgramFile(file), o);

}

// returns number of uncompressed bytes written

static long saveGZStructureToFile(File file, O o, structure_Data data default new) ctex {

  File parentFile = file.getParentFile();

  if (parentFile != null)

    parentFile.mkdirs();

  File tempFile = tempFileFor(file);

  if (tempFile.exists()) try {

    S saveName = tempFile.getPath() + ".saved." + now();

    copyFile(tempFile, new File(saveName));

  } catch (Throwable e) { printStackTrace(e); }

  FileOutputStream fileOutputStream = newFileOutputStream(tempFile.getPath());

  CountingOutputStream cos;

  try {

    GZIPOutputStream gos = new GZIPOutputStream(fileOutputStream);

    cos = new CountingOutputStream(gos);

    OutputStreamWriter outputStreamWriter = new OutputStreamWriter(cos, "UTF-8");

    PrintWriter printWriter = new PrintWriter(outputStreamWriter);

    structureToPrintWriter(o, printWriter, data);

    printWriter.close();

    gos.close();

    fileOutputStream.close();

  } catch e {

    fileOutputStream.close();

    tempFile.delete();

    throw rethrow(e);

  }

  if (file.exists() && !file.delete())

    throw new IOException("Can't delete " + file.getPath());

  if (!tempFile.renameTo(file))

    throw new IOException("Can't rename " + tempFile + " to " + file);

  ret cos.getFilePointer();

}