#include <nghttp2/nghttp2.h>

int32_t nghttp2_submit_headers(nghttp2_session *session, uint8_t flags, int32_t stream_id, const nghttp2_priority_spec *pri_spec, const nghttp2_nv *nva, size_t nvlen, void *stream_user_data)

Submits HEADERS frame. The flags is bitwise OR of the following values:

If flags includes nghttp2_flag.NGHTTP2_FLAG_END_STREAM, this frame has END_STREAM flag set.

The library handles the CONTINUATION frame internally and it correctly sets END_HEADERS to the last sequence of the PUSH_PROMISE or CONTINUATION frame.

If the stream_id is -1, this frame is assumed as request (i.e., request HEADERS frame which opens new stream). In this case, the assigned stream ID will be returned. Otherwise, specify stream ID in stream_id.

The pri_spec is a deprecated priority specification of this request. NULL means the default priority (see nghttp2_priority_spec_default_init()). To specify the priority, use nghttp2_priority_spec_init(). If pri_spec is not NULL, this function will copy its data members. In the future release after the end of 2024, this function will ignore pri_spec and behave as if NULL is given.

The pri_spec->weight must be in [NGHTTP2_MIN_WEIGHT, NGHTTP2_MAX_WEIGHT], inclusive. If pri_spec->weight is strictly less than NGHTTP2_MIN_WEIGHT, it becomes NGHTTP2_MIN_WEIGHT. If it is strictly greater than NGHTTP2_MAX_WEIGHT, it becomes NGHTTP2_MAX_WEIGHT.

If nghttp2_settings_id.NGHTTP2_SETTINGS_NO_RFC7540_PRIORITIES of value of 1 is received by a remote endpoint, pri_spec is ignored, and treated as if NULL is specified.

The nva is an array of name/value pair nghttp2_nv with nvlen elements. The application is responsible to include required pseudo-header fields (header field whose name starts with ":") in nva and must place pseudo-headers before regular header fields.

This function creates copies of all name/value pairs in nva. It also lower-cases all names in nva. The order of elements in nva is preserved. For header fields with nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_NAME and nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_VALUE are set, header field name and value are not copied respectively. With nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_NAME, application is responsible to pass header field name in lowercase. The application should maintain the references to them until nghttp2_on_frame_send_callback or nghttp2_on_frame_not_send_callback is called.

The stream_user_data is a pointer to an arbitrary data which is associated to the stream this frame will open. Therefore it is only used if this frame opens streams, in other words, it changes stream state from idle or reserved to open.

This function is low-level in a sense that the application code can specify flags directly. For usual HTTP request, nghttp2_submit_request2() is useful. Likewise, for HTTP response, prefer nghttp2_submit_response2().

This function returns newly assigned stream ID if it succeeds and stream_id is -1. Otherwise, this function returns 0 if it succeeds, or one of the following negative error codes:


Out of memory.


No stream ID is available because maximum stream ID was reached.


The stream_id is 0; or trying to depend on itself (stream ID equals pri_spec->stream_id).


DATA or HEADERS has been already submitted and not fully processed yet. This happens if stream denoted by stream_id is in reserved state.


The stream_id is -1, and session is server session.


This function returns assigned stream ID if it succeeds and stream_id is -1. But that stream is not opened yet. The application must not submit frame to that stream ID before nghttp2_before_frame_send_callback is called for this frame.