oldXMenu/insque.c

   1 /*
   2 Copyright (C) 1993-1998, 2001-2017 Free Software Foundation, Inc.
   3
   4 This program is free software: you can redistribute it and/or modify
   5 it under the terms of the GNU General Public License as published by
   6 the Free Software Foundation, either version 3 of the License, or (at
   7 your option) any later version.
   8
   9 This program 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
  12 GNU General Public License for more details.
  13
  14 You should have received a copy of the GNU General Public License
  15 along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  16
  17 /* This file implements the emacs_insque and emacs_remque functions,
  18    clones of the insque and remque functions of BSD.  They and all
  19    their callers have been renamed to emacs_mumble to allow us to
  20    include this file in the menu library on all systems.  */
  21
  22 #include "XMenuInt.h"
  23
  24 struct qelem {
  25   struct    qelem *q_forw;
  26   struct    qelem *q_back;
  27   char q_data[1];
  28 };
  29
  30 /* Insert ELEM into a doubly-linked list, after PREV.  */
  31
  32 void
  33 emacs_insque (void *velem, void *vprev)
  34 {
  35   struct qelem *elem = velem;
  36   struct qelem *prev = vprev;
  37   struct qelem *next = prev->q_forw;
  38   prev->q_forw = elem;
  39   if (next)
  40     next->q_back = elem;
  41   elem->q_forw = next;
  42   elem->q_back = prev;
  43 }
  44
  45 /* Unlink ELEM from the doubly-linked list that it is in.  */
  46
  47 void
  48 emacs_remque (void *velem)
  49 {
  50   struct qelem *elem = velem;
  51   struct qelem *next = elem->q_forw;
  52   struct qelem *prev = elem->q_back;
  53   if (next)
  54     next->q_back = prev;
  55   if (prev)
  56     prev->q_forw = next;
  57 }