code: @Override
      public int readArrayB(DeMember member, byte[] typevals, Decodeable componentDecoder) { //componentDecoder可能为null
          short bt = readShort();
          if (bt == Reader.SIGN_NULL) return bt;
          int rs = (bt & 0xffff) << 16 | ((content[++this.position] & 0xff) << 8) | (content[++this.position] & 0xff);
          if (componentDecoder != null && componentDecoder != ByteSimpledCoder.instance) {
              byte comval = readByte();
              if (typevals != null) typevals[0] = comval;
          }
          return rs;
      }
docs: 判断下一个非空白字节是否为[
  
  @return 数组长度或SIGN_NULL