misc/insremque.c

   1 /* Copyright (C) 1992 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 Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 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 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <stddef.h>
  21
  22 struct qelem
  23   {
  24     struct qelem *q_forw;
  25     struct qelem *q_back;
  26     char q_data[1];
  27   };
  28
  29 /* Insert ELEM into a doubly-linked list, after PREV.  */
  30
  31 void
  32 DEFUN(insque, (elem, prev) ,
  33       struct qelem *elem AND struct qelem *prev)
  34 {
  35   struct qelem *next = prev->q_forw;
  36   prev->q_forw = elem;
  37   if (next != NULL)
  38     next->q_back = elem;
  39   elem->q_forw = next;
  40   elem->q_back = prev;
  41 }
  42
  43 /* Unlink ELEM from the doubly-linked list that it is in.  */
  44
  45 void
  46 DEFUN(remque, (elem),
  47       struct qelem *elem)
  48 {
  49   struct qelem *next = elem->q_forw;
  50   struct qelem *prev = elem->q_back;
  51   if (next != NULL)
  52     next->q_back = prev;
  53   if (prev != NULL)
  54     prev->q_forw = next;
  55 }