Add nghttp2_session_{set,get}_next_stream_id API function

lib/includes/nghttp2/nghttp2.h

@@ -2435,6 +2435,32 @@ int nghttp2_session_terminate_session2(nghttp2_session *session,
 uint32_t nghttp2_session_get_remote_settings(nghttp2_session *session,
                                              nghttp2_settings_id id);
 
+/**
+ * @function
+ *
+ * Tells the |session| that next stream ID is |next_stream_id|.  The
+ * |next_stream_id| must be equal or greater than the value returned
+ * by `nghttp2_session_get_next_stream_id()`.
+ *
+ * This function returns 0 if it succeeds, or one of the following
+ * negative error codes:
+ *
+ * :enum:`NGHTTP2_ERR_INVALID_ARGUMENT`
+ *     The |next_stream_id| is strictly less than the value
+ *     `nghttp2_session_get_next_stream_id()` returns.
+ */
+int nghttp2_session_set_next_stream_id(nghttp2_session *session,
+                                       int32_t next_stream_id);
+
+/**
+ * @function
+ *
+ * Returns the next outgoing stream ID.  Notice that return type is
+ * uint32_t.  If we run out of stream ID for this session, this
+ * function returns 1 << 31.
+ */
+uint32_t nghttp2_session_get_next_stream_id(nghttp2_session *session);
+
 /**
  * @function
  *

lib/nghttp2_session.c

@@ -6158,3 +6158,18 @@ int nghttp2_session_consume(nghttp2_session *session, int32_t stream_id,
 
   return 0;
 }
+
+int nghttp2_session_set_next_stream_id(nghttp2_session *session,
+                                       int32_t next_stream_id) {
+  if (next_stream_id < 0 ||
+      session->next_stream_id > (uint32_t)next_stream_id) {
+    return NGHTTP2_ERR_INVALID_ARGUMENT;
+  }
+
+  session->next_stream_id = next_stream_id;
+  return 0;
+}
+
+uint32_t nghttp2_session_get_next_stream_id(nghttp2_session *session) {
+  return session->next_stream_id;
+}