1 /* ========================================================================== **
4 * Copyright (C) 1997, 1998 by Christopher R. Hertel
6 * Email: crh@ubiqx.mn.org
7 * -------------------------------------------------------------------------- **
8 * This module implements a simple singly-linked list.
9 * -------------------------------------------------------------------------- **
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.
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.
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.
25 * -------------------------------------------------------------------------- **
27 * Log: ubi_sLinkList.c,v
28 * Revision 0.5 1998/05/20 04:38:05 crh
29 * The C file now includes ubi_null.h. See ubi_null.h for more info.
31 * Revision 0.4 1998/03/10 02:23:20 crh
32 * Combined ubi_StackQueue and ubi_sLinkList into one module. Redesigned
33 * the functions and macros. Not a complete rewrite but close to it.
35 * Revision 0.3 1998/01/03 01:59:52 crh
36 * Added ubi_slCount() macro.
38 * Revision 0.2 1997/10/21 03:35:18 crh
39 * Added parameter <After> in function Insert(). Made necessary changes
40 * to macro AddHead() and added macro AddHere().
42 * Revision 0.1 1997/10/16 02:53:45 crh
45 * -------------------------------------------------------------------------- **
46 * This module implements a singly-linked list which may also be used as a
47 * queue or a stack. For a queue, entries are added at the tail and removed
48 * from the head of the list. For a stack, the entries are entered and
49 * removed from the head of the list. A traversal of the list will always
50 * start at the head of the list and proceed toward the tail. This is all
51 * mind-numbingly simple, but I'm surprised by the number of programs out
52 * there which re-implement this a dozen or so times.
54 * Notes: When the list header is initialized, the Tail pointer is set to
55 * point to the Head pointer. This simplifies things a great deal,
56 * except that you can't initialize a stack or queue by simply
57 * zeroing it out. One sure way to initialize the header is to call
58 * ubi_slInit(). Another option would be something like this:
60 * static ubi_slList MyList = { NULL, (ubi_slNodePtr)&MyList, 0 };
62 * See ubi_slInit() and the ubi_slList structure for more info.
64 * + Also, note that this module is similar to the ubi_dLinkList
65 * module. There are three key differences:
66 * - This is a singly-linked list, the other is a doubly-linked
68 * - In this module, if the list is empty, the tail pointer will
69 * point back to the head of the list as described above. This
70 * is not done in ubi_dLinkList.
71 * - The ubi_slRemove() function, by necessity, removed the 'next'
72 * node. In ubi_dLinkList, the ubi_dlRemove() function removes
75 * ========================================================================== **
78 #include "ubi_null.h" /* ubiqx NULL source. */
79 #include "ubi_sLinkList.h" /* Header for *this* module. */
81 /* ========================================================================== **
85 ubi_slListPtr ubi_slInitList( ubi_slListPtr ListPtr )
86 /* ------------------------------------------------------------------------ **
87 * Initialize a singly-linked list header.
89 * Input: ListPtr - A pointer to the list structure that is to be
90 * initialized for use.
92 * Output: A pointer to the initialized list header (i.e., same as
95 * ------------------------------------------------------------------------ **
99 ListPtr->Tail = (ubi_slNodePtr)ListPtr;
102 } /* ubi_slInitList */
104 ubi_slNodePtr ubi_slInsert( ubi_slListPtr ListPtr,
106 ubi_slNodePtr After )
107 /* ------------------------------------------------------------------------ **
108 * Add a node to the list.
110 * Input: ListPtr - A pointer to the list into which the node is to
112 * New - Pointer to the node that is to be added to the list.
113 * After - Pointer to a list in a node after which the new node
114 * will be inserted. If NULL, then the new node will
115 * be added at the head of the list.
117 * Output: A pointer to the node that was inserted into the list (i.e.,
118 * the same as <New>).
120 * ------------------------------------------------------------------------ **
123 After = After ? After : (ubi_slNodePtr)ListPtr;
124 New->Next = After->Next;
132 ubi_slNodePtr ubi_slRemove( ubi_slListPtr ListPtr, ubi_slNodePtr After )
133 /* ------------------------------------------------------------------------ **
134 * Remove the node followng <After>. If <After> is NULL, remove from the
137 * Input: ListPtr - A pointer to the list from which the node is to be
139 * After - Pointer to the node preceeding the node to be
142 * Output: A pointer to the node that was removed, or NULL if the list is
145 * ------------------------------------------------------------------------ **
148 ubi_slNodePtr DelNode;
150 After = After ? After : (ubi_slNodePtr)ListPtr;
151 DelNode = After->Next;
154 if( !(DelNode->Next) )
155 ListPtr->Tail = After;
156 After->Next = DelNode->Next;
162 /* ================================ The End ================================= */