CURLcode curl_easy_setopt(CURL *handle, CURLOPT_STREAM_DEPENDS_E, CURL *dephandle);
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.
CURL *curl = curl_easy_init();
CURL *curl2 = curl_easy_init(); /* a second handle */
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/one");
/* the second depends on the first */
curl_easy_setopt(curl2, CURLOPT_URL, "https://example.com/two");
curl_easy_setopt(curl2, CURLOPT_STREAM_DEPENDS_E, curl);
/* then add both to a multi handle and transfer them! */
}