misc/insremque.c

   1 /* Copyright (C) 1992, 1995, 1996, 2006 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <stddef.h>
  20 #include <search.h>
  21
  22 /* Insert ELEM into a doubly-linked list, after PREV.  */
  23
  24 void
  25 insque (void *elem, void *prev)
  26 {
  27   if (prev == NULL)
  28     {
  29       ((struct qelem *) elem)->q_forw = NULL;
  30       ((struct qelem *) elem)->q_back = NULL;
  31     }
  32   else
  33     {
  34       struct qelem *next = ((struct qelem *) prev)->q_forw;
  35       ((struct qelem *) prev)->q_forw = (struct qelem *) elem;
  36       if (next != NULL)
  37         next->q_back = (struct qelem *) elem;
  38       ((struct qelem *) elem)->q_forw = next;
  39       ((struct qelem *) elem)->q_back = (struct qelem *) prev;
  40     }
  41 }
  42
  43 /* Unlink ELEM from the doubly-linked list that it is in.  */
  44
  45 void
  46 remque (void *elem)
  47 {
  48   struct qelem *next = ((struct qelem *) elem)->q_forw;
  49   struct qelem *prev = ((struct qelem *) elem)->q_back;
  50   if (next != NULL)
  51     next->q_back = prev;
  52   if (prev != NULL)
  53     prev->q_forw = (struct qelem *) next;
  54 }