1 /* $NetBSD: lstConcat.c,v 1.16 2008/12/13 15:19:29 dsl Exp $ */
2
3 /*
4 * Copyright (c) 1988, 1989, 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Adam de Boor.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #ifndef MAKE_NATIVE
36 static char rcsid[] = "$NetBSD: lstConcat.c,v 1.16 2008/12/13 15:19:29 dsl Exp $";
37 #else
38 #include <sys/cdefs.h>
39 #ifndef lint
40 #if 0
41 static char sccsid[] = "@(#)lstConcat.c 8.1 (Berkeley) 6/6/93";
42 #else
43 __RCSID("$NetBSD: lstConcat.c,v 1.16 2008/12/13 15:19:29 dsl Exp $");
44 #endif
45 #endif /* not lint */
46 #endif
47
48 /*-
49 * listConcat.c --
50 * Function to concatentate two lists.
51 */
52
53 #include "lstInt.h"
54
55 /*-
56 *-----------------------------------------------------------------------
57 * Lst_Concat --
58 * Concatenate two lists. New elements are created to hold the data
59 * elements, if specified, but the elements themselves are not copied.
60 * If the elements should be duplicated to avoid confusion with another
61 * list, the Lst_Duplicate function should be called first.
62 * If LST_CONCLINK is specified, the second list is destroyed since
63 * its pointers have been corrupted and the list is no longer useable.
64 *
65 * Input:
66 * l1 The list to which l2 is to be appended
67 * l2 The list to append to l1
68 * flags LST_CONCNEW if LstNode's should be duplicated
69 * LST_CONCLINK if should just be relinked
70 *
71 * Results:
72 * SUCCESS if all went well. FAILURE otherwise.
73 *
74 * Side Effects:
75 * New elements are created and appended the first list.
76 *-----------------------------------------------------------------------
77 */
78 ReturnStatus
Lst_Concat(Lst l1,Lst l2,int flags)79 Lst_Concat(Lst l1, Lst l2, int flags)
80 {
81 ListNode ln; /* original LstNode */
82 ListNode nln; /* new LstNode */
83 ListNode last; /* the last element in the list. Keeps
84 * bookkeeping until the end */
85 List list1 = l1;
86 List list2 = l2;
87
88 if (!LstValid (l1) || !LstValid (l2)) {
89 return (FAILURE);
90 }
91
92 if (flags == LST_CONCLINK) {
93 if (list2->firstPtr != NULL) {
94 /*
95 * We set the nextPtr of the
96 * last element of list two to be NIL to make the loop easier and
97 * so we don't need an extra case should the first list turn
98 * out to be non-circular -- the final element will already point
99 * to NIL space and the first element will be untouched if it
100 * existed before and will also point to NIL space if it didn't.
101 */
102 list2->lastPtr->nextPtr = NULL;
103 /*
104 * So long as the second list isn't empty, we just link the
105 * first element of the second list to the last element of the
106 * first list. If the first list isn't empty, we then link the
107 * last element of the list to the first element of the second list
108 * The last element of the second list, if it exists, then becomes
109 * the last element of the first list.
110 */
111 list2->firstPtr->prevPtr = list1->lastPtr;
112 if (list1->lastPtr != NULL) {
113 list1->lastPtr->nextPtr = list2->firstPtr;
114 } else {
115 list1->firstPtr = list2->firstPtr;
116 }
117 list1->lastPtr = list2->lastPtr;
118 }
119 if (list1->isCirc && list1->firstPtr != NULL) {
120 /*
121 * If the first list is supposed to be circular and it is (now)
122 * non-empty, we must make sure it's circular by linking the
123 * first element to the last and vice versa
124 */
125 list1->firstPtr->prevPtr = list1->lastPtr;
126 list1->lastPtr->nextPtr = list1->firstPtr;
127 }
128 free(l2);
129 } else if (list2->firstPtr != NULL) {
130 /*
131 * We set the nextPtr of the last element of list 2 to be nil to make
132 * the loop less difficult. The loop simply goes through the entire
133 * second list creating new LstNodes and filling in the nextPtr, and
134 * prevPtr to fit into l1 and its datum field from the
135 * datum field of the corresponding element in l2. The 'last' node
136 * follows the last of the new nodes along until the entire l2 has
137 * been appended. Only then does the bookkeeping catch up with the
138 * changes. During the first iteration of the loop, if 'last' is nil,
139 * the first list must have been empty so the newly-created node is
140 * made the first node of the list.
141 */
142 list2->lastPtr->nextPtr = NULL;
143 for (last = list1->lastPtr, ln = list2->firstPtr;
144 ln != NULL;
145 ln = ln->nextPtr)
146 {
147 PAlloc (nln, ListNode);
148 nln->datum = ln->datum;
149 if (last != NULL) {
150 last->nextPtr = nln;
151 } else {
152 list1->firstPtr = nln;
153 }
154 nln->prevPtr = last;
155 nln->flags = nln->useCount = 0;
156 last = nln;
157 }
158
159 /*
160 * Finish bookkeeping. The last new element becomes the last element
161 * of list one.
162 */
163 list1->lastPtr = last;
164
165 /*
166 * The circularity of both list one and list two must be corrected
167 * for -- list one because of the new nodes added to it; list two
168 * because of the alteration of list2->lastPtr's nextPtr to ease the
169 * above for loop.
170 */
171 if (list1->isCirc) {
172 list1->lastPtr->nextPtr = list1->firstPtr;
173 list1->firstPtr->prevPtr = list1->lastPtr;
174 } else {
175 last->nextPtr = NULL;
176 }
177
178 if (list2->isCirc) {
179 list2->lastPtr->nextPtr = list2->firstPtr;
180 }
181 }
182
183 return (SUCCESS);
184 }
185
186