code: private byte[] digestWithoutSalt(InputStream data, int bufferLength) throws IOException {
  		final byte[] buffer = new byte[bufferLength];
  		int read;
  		while ((read = data.read(buffer, 0, bufferLength)) > -1) {
  			this.digest.update(buffer, 0, read);
  		}
  		return this.digest.digest();
  	}
docs: 生成摘要
  
  @param data {@link InputStream} 数据流
  @param bufferLength 缓存长度，不足1使用 {@link IoUtil#DEFAULT_BUFFER_SIZE} 做为默认值
  @return 摘要bytes
  @throws IOException 从流中读取数据引发的IO异常