gnu/dist/gdb6/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}, struct qelem *@var{pred})
   7 @deftypefnx Supplemental void remque (struct qelem *@var{elem})
   8
   9 Routines to manipulate queues built from doubly linked lists.  The
  10 @code{insque} routine inserts @var{elem} in the queue immediately
  11 after @var{pred}.  The @code{remque} routine removes @var{elem} from
  12 its containing queue.  These routines expect to be passed pointers to
  13 structures which have as their first members a forward pointer and a
  14 back pointer, like this prototype (although no prototype is provided):
  15
  16 @example
  17 struct qelem @{
  18   struct qelem *q_forw;
  19   struct qelem *q_back;
  20   char q_data[];
  21 @};
  22 @end example
  23
  24 @end deftypefn
  25
  26 */
  27
  28
  29 struct qelem {
  30   struct qelem *q_forw;
  31   struct qelem *q_back;
  32 };
  33
  34
  35 void
  36 insque (struct qelem *elem, struct qelem *pred)
  37 {
  38   elem -> q_forw = pred -> q_forw;
  39   pred -> q_forw -> q_back = elem;
  40   elem -> q_back = pred;
  41   pred -> q_forw = elem;
  42 }
  43
  44
  45 void
  46 remque (struct qelem *elem)
  47 {
  48   elem -> q_forw -> q_back = elem -> q_back;
  49   elem -> q_back -> q_forw = elem -> q_forw;
  50 }