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/* insque(3C) routines
This file is in the public domain. */
@deftypefn Supplemental void insque (struct qelem *@var{elem}, struct qelem *@var{pred})
@deftypefnx Supplemental void remque (struct qelem *@var{elem})
Routines to manipulate queues built from doubly linked lists. The
@code{insque} routine inserts @var{elem} in the queue immediately
after @var{pred}. The @code{remque} routine removes @var{elem} from
its containing queue. These routines expect to be passed pointers to
structures which have as their first members a forward pointer and a
back pointer, like this prototype (although no prototype is provided):
struct qelem @{
struct qelem *q_forw;
struct qelem *q_back;
char q_data[];
@end example
@end deftypefn
struct qelem {
struct qelem *q_forw;
struct qelem *q_back;
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;
remque (elem)
struct qelem *elem;
elem -> q_forw -> q_back = elem -> q_back;
elem -> q_back -> q_forw = elem -> q_forw;