nghttp2多部分POST消息

我目前正在尝试使用nghttp2构建多部分消息.该消息应该如下所示.

我应该使用nghttp2_submit_request(here)函数,nva作为我的HTTP/2标头,以及nghttp2_data_provider *data_prd我的数据.但是,我仍然不明白我究竟能创建两条消息(带有两个消息头).

更新:

我可以在源代码中描述我的想法吗？请看下面.在这里,我nghttp2_data_provider用来打开一个音频文件,然后写入缓冲区.

ssize_t data_prd_read_callback(
    nghttp2_session *session, int32_t stream_id, uint8_t *buf, size_t length,
    uint32_t *data_flags, nghttp2_data_source *source, void *user_data) 
{

  printf("[INFO] C ----------------------------> S (DATA post body), length:%zu\n", length);

  int fd = source->fd;
  ssize_t r;
// writting my opened audio file into buffer
  while ((r = read(fd, buf, length)) == -1 && errno == EINTR); 
  printf("stream_id:%d, nread:%zu\r\n", stream_id, r);
  return nread;
}



void submit_postAudio(http2_session_data *session_data) {
  int32_t stream_id;
  http2_stream_data *stream_data = session_data->stream_data[STREAM_ID_REQUESTAUDIO];
  const char *uri = stream_data->uri;
  const struct http_parser_url *u = stream_data->u;
  char byLength = 0;

  const nghttp2_nv hdrs[] = {
  MAKE_NV(":method", "POST"),   MAKE_NV_CS(":path", stream_data->path),
  MAKE_NV(":scheme", "https"), MAKE_NV("accept", "*/*"),    
  MAKE_NV_CS("authorization", stream_data->access_token),
  MAKE_NV("content-type", "multipart/form-data; boundary=abcdefg123")
  };

  fprintf(stderr, "Request headers:\n");
  print_headers(stderr, hdrs, ARRLEN(hdrs));

  int fileDescriptor = open ("/my_audio.wmv", O_APPEND);  // open my audio file 
  nghttp2_data_provider data_prd;
  data_prd.source.fd = fileDescriptor   // set the file descriptor 
  data_prd.source.ptr = NULL;
  data_prd.read_callback = data_prd_read_callback;

  stream_id = nghttp2_submit_request(session_data->session, NULL, hdrs,
                                     ARRLEN(hdrs), &data_prd, stream_data);
  if (stream_id <0) {
    errx(1, "Could not submit HTTP request: %s", nghttp2_strerror(stream_id));
  }

  stream_data->stream_id = stream_id;
}

困扰我的是1)如何向音频添加标题(更具体的消息标题).2)如何在我的Json文件后追加它.