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/* ========================================================================== **
* ubi_sLinkList.c
*
* Copyright (C) 1997, 1998 by Christopher R. Hertel
*
* Email: crh@ubiqx.mn.org
* -------------------------------------------------------------------------- **
* This module implements a simple singly-linked list.
* -------------------------------------------------------------------------- **
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* -------------------------------------------------------------------------- **
*
* Log: ubi_sLinkList.c,v
* Revision 0.4 1998/03/10 02:23:20 crh
* Combined ubi_StackQueue and ubi_sLinkList into one module. Redesigned
* the functions and macros. Not a complete rewrite but close to it.
*
* Revision 0.3 1998/01/03 01:59:52 crh
* Added ubi_slCount() macro.
*
* Revision 0.2 1997/10/21 03:35:18 crh
* Added parameter <After> in function Insert(). Made necessary changes
* to macro AddHead() and added macro AddHere().
*
* Revision 0.1 1997/10/16 02:53:45 crh
* Initial Revision.
*
* -------------------------------------------------------------------------- **
* This module implements a singly-linked list which may also be used as a
* queue or a stack. For a queue, entries are added at the tail and removed
* from the head of the list. For a stack, the entries are entered and
* removed from the head of the list. A traversal of the list will always
* start at the head of the list and proceed toward the tail. This is all
* mind-numbingly simple, but I'm surprised by the number of programs out
* there which re-implement this a dozen or so times.
*
* Notes: When the list header is initialized, the Tail pointer is set to
* point to the Head pointer. This simplifies things a great deal,
* except that you can't initialize a stack or queue by simply
* zeroing it out. One sure way to initialize the header is to call
* ubi_slInit(). Another option would be something like this:
*
* static ubi_slList MyList = { NULL, (ubi_slNodePtr)&MyList, 0 };
*
* See ubi_slInit() and the ubi_slList structure for more info.
*
* + Also, note that this module is similar to the ubi_dLinkList
* module. There are three key differences:
* - This is a singly-linked list, the other is a doubly-linked
* list.
* - In this module, if the list is empty, the tail pointer will
* point back to the head of the list as described above. This
* is not done in ubi_dLinkList.
* - The ubi_slRemove() function, by necessity, removed the 'next'
* node. In ubi_dLinkList, the ubi_dlRemove() function removes
* the 'current' node.
*
* ========================================================================== **
*/
#include "ubi_sLinkList.h"
/* ========================================================================== **
* Functions...
*/
ubi_slListPtr ubi_slInitList( ubi_slListPtr ListPtr )
/* ------------------------------------------------------------------------ **
* Initialize a singly-linked list header.
*
* Input: ListPtr - A pointer to the list structure that is to be
* initialized for use.
*
* Output: A pointer to the initialized list header (i.e., same as
* <ListPtr>).
*
* ------------------------------------------------------------------------ **
*/
{
ListPtr->Head = NULL;
ListPtr->Tail = (ubi_slNodePtr)ListPtr;
ListPtr->count = 0;
return( ListPtr );
} /* ubi_slInitList */
ubi_slNodePtr ubi_slInsert( ubi_slListPtr ListPtr,
ubi_slNodePtr New,
ubi_slNodePtr After )
/* ------------------------------------------------------------------------ **
* Add a node to the list.
*
* Input: ListPtr - A pointer to the list into which the node is to
* be inserted.
* New - Pointer to the node that is to be added to the list.
* After - Pointer to a list in a node after which the new node
* will be inserted. If NULL, then the new node will
* be added at the head of the list.
*
* Output: A pointer to the node that was inserted into the list (i.e.,
* the same as <New>).
*
* ------------------------------------------------------------------------ **
*/
{
After = After ? After : (ubi_slNodePtr)ListPtr;
New->Next = After->Next;
After->Next = New;
if( !(New->Next) )
ListPtr->Tail = New;
(ListPtr->count)++;
return( New );
} /* ubi_slInsert */
ubi_slNodePtr ubi_slRemove( ubi_slListPtr ListPtr, ubi_slNodePtr After )
/* ------------------------------------------------------------------------ **
* Remove the node followng <After>. If <After> is NULL, remove from the
* head of the list.
*
* Input: ListPtr - A pointer to the list from which the node is to be
* removed.
* After - Pointer to the node preceeding the node to be
* removed.
*
* Output: A pointer to the node that was removed, or NULL if the list is
* empty.
*
* ------------------------------------------------------------------------ **
*/
{
ubi_slNodePtr DelNode;
After = After ? After : (ubi_slNodePtr)ListPtr;
DelNode = After->Next;
if( DelNode )
{
if( !(DelNode->Next) )
ListPtr->Tail = After;
After->Next = DelNode->Next;
(ListPtr->count)--;
}
return( DelNode );
} /* ubi_slRemove */
/* ================================ The End ================================= */
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