docs: public final long parseInteger() {
          int pos = off, radix = 10;
          boolean neg = false;
          if (len > 2 && charAt(0) == '0' && charAt(1) == 'x') {
              pos += 2;
              radix = 16;
          } else if (len > 1 && charAt(0) == '0') {
              pos += 1;
              radix = 8;
          } else if (len > 1 && charAt(0) == '-') {
              neg = true;
              pos += 1;
          }
          long res = 0;
          for (; pos < off + len; ++pos) {
              res *= radix;
              res += validate(fb[pos], valueOfHex(fb[pos]), radix);
          }
          return neg ? -res : res;
      }