void getChars(int start, int end, char @NotNull [] dest, int destPos) {
      int cesure = head.length();
      if (end <= cesure) {
        ImmutableText.getChars(head, start, end, dest, destPos);
      }
      else if (start >= cesure) {
        ImmutableText.getChars(tail, start - cesure, end - cesure, dest, destPos);
      }
      else { // Overlaps head and tail.
        ImmutableText.getChars(head, start, cesure, dest, destPos);
        ImmutableText.getChars(tail, 0, end - cesure, dest, destPos + cesure - start);
      }
    }
void getChars(int start, int end, char @NotNull [] dest, int destPos)