code: private int findLineBreak(Source source) {
          int index;
          int n = source.find(AbstractEol.AN, false);
          int r = source.find(AbstractEol.AR, false);
          if (n >= 0 && r >= 0) {
              index = Math.min(n, r);
          } else if (n >= 0) {
              index = n;
          } else if (r >= 0) {
              index = r;
          } else {
              index = -1;
          }
          return index;
      }
docs: Find first input of line break
  
  @param source the text source