static File lcCompressFilePart(File file, File archiveFile, long startIndex, int length, O... _) {
  optPar bool balancing = true;
  optPar bool fullCompression;
  optPar bool verbose;

  length = toInt(min(length, l(file)-startIndex));
  print("Compressing " + file + " [" + startIndex + "/" + length + "]");
  time "Compressed" {
    new LineCompCompressor compressor;
    compressor.byteMode = true;
    compressor.fullCompression = fullCompression;
    if (fullCompression) print("full compression");
    print("byte mode");
    compressor.verboseCompressionSteps = print(+verbose);
    compressor.balancing = true;
    if (compressor.balancing) print("balancing mode");
    compressor.verify = false;
    compressor.verboseStats = true;
    compressor.loadTexts(litmap(str(startIndex), loadTextFilePart_rawBytes(file, startIndex, startIndex+length));
    compressor.run();
    lcSaveToFile(compressor, archiveFile);
  }
  ret printFileInfo(archiveFile);
}

Began life as a copy of #1029266