int nghttp2_submit_data(nghttp2_session *session, uint8_t flags, int32_t stream_id, const nghttp2_data_provider *data_prd)
Submits one or more DATA frames to the stream stream_id. The data to be sent are provided by data_prd. If flags contains
nghttp2_flag.NGHTTP2_FLAG_END_STREAM, the last DATA frame has END_STREAM flag set.
This function does not take ownership of the data_prd. The function copies the members of the data_prd.
This function returns 0 if it succeeds, or one of the following negative error codes:
Out of memory.
DATA or HEADERS has been already submitted and not fully processed yet.
The stream_id is 0.
The stream was already closed; or the stream_id is invalid.
Currently, only one DATA or HEADERS is allowed for a stream at a time. Submitting these frames more than once before first DATA or HEADERS is finished results in
nghttp2_error.NGHTTP2_ERR_DATA_EXISTerror code. The earliest callback which tells that previous frame is done is
nghttp2_on_frame_send_callback. In side that callback, new data can be submitted using
nghttp2_submit_data(). Of course, all data except for last one must not have
nghttp2_flag.NGHTTP2_FLAG_END_STREAMflag set in flags. This sounds a bit complicated, and we recommend to use
nghttp2_submit_response()to avoid this cascading issue. The experience shows that for HTTP use, these two functions are enough to implement both client and server.