code: private void updateOnlyHeaderBuildDigest(Mac digest) throws IllegalStateException, UnsupportedEncodingException {
          digest.update(Validator.notNull(apiKey, "apiKey not null").getBytes(charset));
          digest.update(delimiter);
          digest.update(Validator.notNull(contentType, "contentType not null").getBytes(charset));
          digest.update(delimiter);
          digest.update(Validator.notNull(date, "date not null").getBytes(charset));
          digest.update(delimiter);
          digest.update(Validator.notNull(host, "host not null").getBytes(charset));
          digest.update(delimiter);
          digest.update(Validator.notNull(method, "method not null").getBytes(charset));
          digest.update(delimiter);
          digest.update(Validator.notNull(nonce, "nonce not null").getBytes(charset));
          digest.update(delimiter);
          digest.update(Validator.notNull(resource, "resource not null").getBytes(charset));
          digest.update(delimiter);
          digest.update(Validator.notNull(scheme, "scheme not null").getBytes(charset));
          digest.update(delimiter);
      }
docs: 仅包含请求头的数据运算