libiberty/insque.c

   1 /* insque(3C) routines
   2    This file is in the public domain.  */
   3
   4 /*
   5
   6 @deftypefn Supplemental void insque (struct qelem *@var{elem}, @
   7   struct qelem *@var{pred})
   8 @deftypefnx Supplemental void remque (struct qelem *@var{elem})
   9
  10 Routines to manipulate queues built from doubly linked lists.  The
  11 @code{insque} routine inserts @var{elem} in the queue immediately
  12 after @var{pred}.  The @code{remque} routine removes @var{elem} from
  13 its containing queue.  These routines expect to be passed pointers to
  14 structures which have as their first members a forward pointer and a
  15 back pointer, like this prototype (although no prototype is provided):
  16
  17 @example
  18 struct qelem @{
  19   struct qelem *q_forw;
  20   struct qelem *q_back;
  21   char q_data[];
  22 @};
  23 @end example
  24
  25 @end deftypefn
  26
  27 */
  28
  29
  30 struct qelem {
  31   struct qelem *q_forw;
  32   struct qelem *q_back;
  33 };
  34
  35
  36 void
  37 insque (struct qelem *elem, struct qelem *pred)
  38 {
  39   elem -> q_forw = pred -> q_forw;
  40   pred -> q_forw -> q_back = elem;
  41   elem -> q_back = pred;
  42   pred -> q_forw = elem;
  43 }
  44
  45
  46 void
  47 remque (struct qelem *elem)
  48 {
  49   elem -> q_forw -> q_back = elem -> q_back;
  50   elem -> q_back -> q_forw = elem -> q_forw;
  51 }