g->prb_color = PRB_RED;
f->prb_color = PRB_BLACK;

g->prb_link[1] = f->prb_link[0];
f->prb_link[0] = g;
h->prb_link[h->prb_link[0] != g] = f;

f->prb_parent = g->prb_parent;
g->prb_parent = f;
if (g->prb_link[1] != NULL)
  g->prb_link[1]->prb_parent = g;
