CURLOPT_STREAM_DEPENDS_E man page
CURLOPT_STREAM_DEPENDS_E — set stream this transfer depends on execlusively
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_STREAM_DEPENDS_E, CURL *dephandle);
Pass a CURL * pointer in dephandle to identify the stream within the same connection that this stream is depending upon exclusively. That means it depends on it and sets the Exclusive bit.
The spec says "Including a dependency expresses a preference to allocate resources to the identified stream rather than to the dependent stream."
Setting a dependency with the exclusive flag for a reprioritized stream causes all the dependencies of the new parent stream to become dependent on the reprioritized stream.
This option can be set during transfer.
dephandle must not be the same as handle, that will cause this function to return an error. It must be another easy handle, and it also needs to be a handle of a transfer that will be sent over the same HTTP/2 connection for this option to have an actual effect.
Added in 7.46.0
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
curl_easy_setopt(3), CURLOPT_STREAM_DEPENDS(3), CURLOPT_STREAM_WEIGHT(3).