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/* insque(3C) routines

   This file is in the public domain.  */

/*

NAME

        insque, remque -- insert, remove an element from a queue

SYNOPSIS

        struct qelem {

          struct qelem *q_forw;

          struct qelem *q_back;

          char q_data[];

        };

        void insque (struct qelem *elem, struct qelem *pred)

        void remque (struct qelem *elem)

DESCRIPTION

        Routines to manipulate queues built from doubly linked lists.

        The insque routine inserts ELEM in the queue immediately after

        PRED.  The remque routine removes ELEM from its containing queue.

*/

struct qelem {

  struct qelem *q_forw;

  struct qelem *q_back;

};

void

insque (elem, pred)

  struct qelem *elem;

  struct qelem *pred;

{

  elem -> q_forw = pred -> q_forw;

  pred -> q_forw -> q_back = elem;

  elem -> q_back = pred;

  pred -> q_forw = elem;

}

void

remque (elem)

  struct qelem *elem;

{

  elem -> q_forw -> q_back = elem -> q_back;

  elem -> q_back -> q_forw = elem -> q_forw;

}