How to modify a single line in a large file?

Question

I have a large .csv file where I need to edit a single value. Is there a way to do that without writing the entire file again?

I know that I can read a file line-by-line like this:

await for (var event in file
      .openRead()
      .transform(utf8.decoder)
      .transform(LineSplitter())) {
    if (isLineToEdit) {
      //edit the line
      break;
    }
  }

However I don't know a way to edit a single line and write that to the file without having to write the entire file again. As far as I know, the only way to write to a file is by either overwriting it (FileMode.write) or by appending at the end (FileMode.append). Am I missing something? Is there some way to do that in dart?