/*  * ring_init(), ring_append(), ring_prepend(), ring_detach(), ring_succ(),  * ring_pred() - circular list management utilities.  *   * Author: Wietse Venema.  */#include "lib.h"/* ring_init - initialize ring head */void    ring_init(ring)RING   *ring;{    ring->pred = ring->succ = ring;}/* ring_append - insert entry after ring head */void    ring_append(ring, entry)RING   *ring;RING   *entry;{    entry->succ = ring->succ;    entry->pred = ring;    ring->succ->pred = entry;    ring->succ = entry;}/* ring_prepend - insert new entry before ring head */void    ring_prepend(ring, entry)RING   *ring;RING   *entry;{    entry->pred = ring->pred;    entry->succ = ring;    ring->pred->succ = entry;    ring->pred = entry;}/* ring_detach - remove entry from ring */void    ring_detach(entry)RING   *entry;{    register RING *succ = entry->succ;    register RING *pred = entry->pred;    pred->succ = succ;    succ->pred = pred;}