source/ubi_dLinkList.c

   1 /* ========================================================================== **
   2  *                              ubi_dLinkList.c
   3  *
   4  *  Copyright (C) 1997 by Christopher R. Hertel
   5  *
   6  *  Email: crh@ubiqx.mn.org
   7  * -------------------------------------------------------------------------- **
   8  *  This module implements simple doubly-linked lists.
   9  * -------------------------------------------------------------------------- **
  10  *
  11  *  This library is free software; you can redistribute it and/or
  12  *  modify it under the terms of the GNU Library General Public
  13  *  License as published by the Free Software Foundation; either
  14  *  version 2 of the License, or (at your option) any later version.
  15  *
  16  *  This library is distributed in the hope that it will be useful,
  17  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19  *  Library General Public License for more details.
  20  *
  21  *  You should have received a copy of the GNU Library General Public
  22  *  License along with this library; if not, write to the Free
  23  *  Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  24  *
  25  * -------------------------------------------------------------------------- **
  26  *
  27  * Revision 0.3  1997/10/15 03:05:39  crh
  28  * Added some handy type casting to the macros.  Added AddHere and RemThis
  29  * macros.
  30  *
  31  * Revision 0.2  1997/10/08 03:07:21  crh
  32  * Fixed a few forgotten link-ups in Insert(), and fixed the AddHead()
  33  * macro, which was passing the wrong value for <After> to Insert().
  34  *
  35  * Revision 0.1  1997/10/07 04:34:07  crh
  36  * Initial Revision.
  37  *
  38  *
  39  * ========================================================================== **
  40  */
  41
  42 #include "ubi_dLinkList.h"
  43
  44 /* ========================================================================== **
  45  * Functions...
  46  */
  47
  48 ubi_dlListPtr ubi_dlInitList( ubi_dlListPtr ListPtr )
  49   /* ------------------------------------------------------------------------ **
  50    * Initialize a doubly-linked list header.
  51    *
  52    *  Input:  ListPtr - A pointer to the list structure that is to be
  53    *                    initialized for use.
  54    *
  55    *  Output: A pointer to the initialized list header (i.e., same as
  56    *          <ListPtr>).
  57    *
  58    * ------------------------------------------------------------------------ **
  59    */
  60   {
  61   ListPtr->Head  = NULL;
  62   ListPtr->Tail  = NULL;
  63   ListPtr->count = 0;
  64   return( ListPtr );
  65   } /* ubi_dlInitList */
  66
  67 ubi_dlNodePtr ubi_dlInsert( ubi_dlListPtr ListPtr,
  68                             ubi_dlNodePtr New,
  69                             ubi_dlNodePtr After )
  70   /* ------------------------------------------------------------------------ **
  71    * Insert a new node into the list.
  72    *
  73    *  Input:  ListPtr - A pointer to the list into which the node is to
  74    *                    be inserted.
  75    *          New     - Pointer to the new node.
  76    *          After   - NULL, or a pointer to a node that is already in the
  77    *                    list.
  78    *                    If NULL, then <New> will be added at the head of the
  79    *                    list, else it will be added following <After>.
  80    *
  81    *  Output: A pointer to the node that was inserted into the list (i.e.,
  82    *          the same as <New>).
  83    *
  84    * ------------------------------------------------------------------------ **
  85    */
  86   {
  87   if( NULL == After )
  88     {
  89     New->Next           = ListPtr->Head;
  90     New->Prev           = NULL;
  91     if( NULL != ListPtr->Head )
  92       ListPtr->Head->Prev = New;
  93     else
  94       ListPtr->Tail       = New;
  95     ListPtr->Head       = New;
  96     }
  97   else
  98     {
  99     New->Next         = After->Next;
 100     New->Prev         = After;
 101     if( NULL != After->Next )
 102       After->Next->Prev = New;
 103     else
 104       ListPtr->Tail       = New;
 105     After->Next       = New;
 106     }
 107
 108   ++(ListPtr->count);
 109
 110   return( New );
 111   } /* ubi_dlInsert */
 112
 113 ubi_dlNodePtr ubi_dlRemove( ubi_dlListPtr ListPtr, ubi_dlNodePtr Old )
 114   /* ------------------------------------------------------------------------ **
 115    * Remove a node from the list.
 116    *
 117    *  Input:  ListPtr - A pointer to the list from which <Old> is to be
 118    *                    removed.
 119    *          Old     - A pointer to the node that is to be removed from the
 120    *                    list.
 121    *
 122    *  Output: A pointer to the node that was removed (i.e., <Old>).
 123    *
 124    * ------------------------------------------------------------------------ **
 125    */
 126   {
 127   if( NULL != Old )
 128     {
 129     if( Old->Next )
 130       Old->Next->Prev = Old->Prev;
 131     else
 132       ListPtr->Tail = Old->Prev;
 133
 134     if( Old->Prev )
 135       Old->Prev->Next = Old->Next;
 136     else
 137       ListPtr->Head = Old->Next;
 138
 139     --(ListPtr->count);
 140     }
 141
 142   return( Old );
 143   } /* ubi_dlRemove */
 144
 145
 146 /* ================================ The End ================================= */