docs: protected void load_raw_characters(StringBuilder sb) throws IOException
      {
          int c = read_char();
          for (;;) {
              c = read_char();
              switch (c) {
              case CharacterSequence.CHAR_SEQ_ESCAPED_NEWLINE_SEQUENCE_1:
              case CharacterSequence.CHAR_SEQ_ESCAPED_NEWLINE_SEQUENCE_2:
              case CharacterSequence.CHAR_SEQ_ESCAPED_NEWLINE_SEQUENCE_3:
              // WAS: case IonTokenConstsX.ESCAPED_NEWLINE_SEQUENCE:
                  continue;
              case -1:
                  return;
              default:
                  if (!IonTokenConstsX.is7bitValue(c)) {
                      c = read_large_char_sequence(c);
                  }
              }
              if (IonUTF8.needsSurrogateEncoding(c)) {
                  sb.append(IonUTF8.highSurrogate(c));
                  c = IonUTF8.lowSurrogate(c);
              }
              sb.append((char)c);
          }
      }