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1 | /* |
2 | * Copyright (c) 1988, 1989, 1990 The Regents of the University of California. | |
3 | * All rights reserved. | |
c65fedcf | 4 | * |
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5 | * This code is derived from software contributed to Berkeley by |
6 | * Adam de Boor. | |
c65fedcf | 7 | * |
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8 | * Redistribution and use in source and binary forms are permitted |
9 | * provided that the above copyright notice and this paragraph are | |
10 | * duplicated in all such forms and that any documentation, | |
11 | * advertising materials, and other materials related to such | |
12 | * distribution and use acknowledge that the software was developed | |
13 | * by the University of California, Berkeley. The name of the | |
14 | * University may not be used to endorse or promote products derived | |
15 | * from this software without specific prior written permission. | |
16 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR | |
17 | * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED | |
18 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. | |
c65fedcf | 19 | */ |
bb2109e7 | 20 | |
c65fedcf | 21 | #ifndef lint |
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22 | static char sccsid[] = "@(#)lstConcat.c 5.2 (Berkeley) %G%"; |
23 | #endif /* not lint */ | |
24 | ||
25 | /*- | |
26 | * listConcat.c -- | |
27 | * Function to concatentate two lists. | |
28 | */ | |
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29 | |
30 | #include "lstInt.h" | |
31 | ||
32 | /*- | |
33 | *----------------------------------------------------------------------- | |
34 | * Lst_Concat -- | |
35 | * Concatenate two lists. New elements are created to hold the data | |
36 | * elements, if specified, but the elements themselves are not copied. | |
37 | * If the elements should be duplicated to avoid confusion with another | |
38 | * list, the Lst_Duplicate function should be called first. | |
39 | * If LST_CONCLINK is specified, the second list is destroyed since | |
40 | * its pointers have been corrupted and the list is no longer useable. | |
41 | * | |
42 | * Results: | |
43 | * SUCCESS if all went well. FAILURE otherwise. | |
44 | * | |
45 | * Side Effects: | |
46 | * New elements are created and appended the the first list. | |
47 | *----------------------------------------------------------------------- | |
48 | */ | |
49 | ReturnStatus | |
50 | Lst_Concat (l1, l2, flags) | |
51 | Lst l1; /* The list to which l2 is to be appended */ | |
52 | Lst l2; /* The list to append to l1 */ | |
53 | int flags; /* LST_CONCNEW if LstNode's should be duplicated | |
54 | * LST_CONCLINK if should just be relinked */ | |
55 | { | |
56 | register ListNode ln; /* original LstNode */ | |
57 | register ListNode nln; /* new LstNode */ | |
58 | register ListNode last; /* the last element in the list. Keeps | |
59 | * bookkeeping until the end */ | |
60 | register List list1 = (List)l1; | |
61 | register List list2 = (List)l2; | |
62 | ||
63 | if (!LstValid (l1) || !LstValid (l2)) { | |
64 | return (FAILURE); | |
65 | } | |
66 | ||
67 | if (flags == LST_CONCLINK) { | |
68 | if (list2->firstPtr != NilListNode) { | |
69 | /* | |
70 | * We set the nextPtr of the | |
71 | * last element of list two to be NIL to make the loop easier and | |
72 | * so we don't need an extra case should the first list turn | |
73 | * out to be non-circular -- the final element will already point | |
74 | * to NIL space and the first element will be untouched if it | |
75 | * existed before and will also point to NIL space if it didn't. | |
76 | */ | |
77 | list2->lastPtr->nextPtr = NilListNode; | |
78 | /* | |
79 | * So long as the second list isn't empty, we just link the | |
80 | * first element of the second list to the last element of the | |
81 | * first list. If the first list isn't empty, we then link the | |
82 | * last element of the list to the first element of the second list | |
83 | * The last element of the second list, if it exists, then becomes | |
84 | * the last element of the first list. | |
85 | */ | |
86 | list2->firstPtr->prevPtr = list1->lastPtr; | |
87 | if (list1->lastPtr != NilListNode) { | |
88 | list1->lastPtr->nextPtr = list2->firstPtr; | |
89 | } | |
90 | list1->lastPtr = list2->lastPtr; | |
91 | } | |
92 | if (list1->isCirc && list1->firstPtr != NilListNode) { | |
93 | /* | |
94 | * If the first list is supposed to be circular and it is (now) | |
95 | * non-empty, we must make sure it's circular by linking the | |
96 | * first element to the last and vice versa | |
97 | */ | |
98 | list1->firstPtr->prevPtr = list1->lastPtr; | |
99 | list1->lastPtr->nextPtr = list1->firstPtr; | |
100 | } | |
101 | free ((Address)l2); | |
102 | } else if (list2->firstPtr != NilListNode) { | |
103 | /* | |
104 | * We set the nextPtr of the last element of list 2 to be nil to make | |
105 | * the loop less difficult. The loop simply goes through the entire | |
106 | * second list creating new LstNodes and filling in the nextPtr, and | |
107 | * prevPtr to fit into l1 and its datum field from the | |
108 | * datum field of the corresponding element in l2. The 'last' node | |
109 | * follows the last of the new nodes along until the entire l2 has | |
110 | * been appended. Only then does the bookkeeping catch up with the | |
111 | * changes. During the first iteration of the loop, if 'last' is nil, | |
112 | * the first list must have been empty so the newly-created node is | |
113 | * made the first node of the list. | |
114 | */ | |
115 | list2->lastPtr->nextPtr = NilListNode; | |
116 | for (last = list1->lastPtr, ln = list2->firstPtr; | |
117 | ln != NilListNode; | |
118 | ln = ln->nextPtr) | |
119 | { | |
120 | PAlloc (nln, ListNode); | |
121 | nln->datum = ln->datum; | |
122 | if (last != NilListNode) { | |
123 | last->nextPtr = nln; | |
124 | } else { | |
125 | list1->firstPtr = nln; | |
126 | } | |
127 | nln->prevPtr = last; | |
128 | nln->flags = nln->useCount = 0; | |
129 | last = nln; | |
130 | } | |
131 | ||
132 | /* | |
133 | * Finish bookkeeping. The last new element becomes the last element | |
134 | * of list one. | |
135 | */ | |
136 | list1->lastPtr = last; | |
137 | ||
138 | /* | |
139 | * The circularity of both list one and list two must be corrected | |
140 | * for -- list one because of the new nodes added to it; list two | |
141 | * because of the alteration of list2->lastPtr's nextPtr to ease the | |
142 | * above for loop. | |
143 | */ | |
144 | if (list1->isCirc) { | |
145 | list1->lastPtr->nextPtr = list1->firstPtr; | |
146 | list1->firstPtr->prevPtr = list1->lastPtr; | |
147 | } else { | |
148 | last->nextPtr = NilListNode; | |
149 | } | |
150 | ||
151 | if (list2->isCirc) { | |
152 | list2->lastPtr->nextPtr = list2->firstPtr; | |
153 | } | |
154 | } | |
155 | ||
156 | return (SUCCESS); | |
157 | } | |
158 |