code: public void write(ByteBuffer buffer, int len) {
          if (len < 1) return;
          if (count >= content.length - len) {
              byte[] ns = new byte[content.length + len];
              System.arraycopy(content, 0, ns, 0, count);
              this.content = ns;
          }
          buffer.get(content, count, len);
          count += len;
      }
docs: 写入ByteBuffer指定长度的数据
  
  @param buffer 数据
  @param len    指定长度