code: @Override
      public final int readMapB(DeMember member, byte[] typevals, Decodeable keyDecoder, Decodeable valuedecoder) {
          return readArrayB(member, typevals, keyDecoder);
      }
docs: 判断下一个非空白字符是否为{
  
  @param member       DeMember
  @param typevals     byte[]
  @param keyDecoder   Decodeable
  @param valuedecoder Decodeable
  
  @return SIGN_NOLENGTH 或 SIGN_NULL