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36 * $FreeBSD: src/usr.bin/make/lst.lib/lstConcat.c,v 1.7 1999/08/28 01:03:47 peter Exp $
37 * $DragonFly: src/usr.bin/make/lst.lib/Attic/lstConcat.c,v 1.2 2003/06/17 04:29:29 dillon Exp $
39 * @(#)lstConcat.c 8.1 (Berkeley) 6/6/93
44 * Function to concatentate two lists.
50 *-----------------------------------------------------------------------
52 * Concatenate two lists. New elements are created to hold the data
53 * elements, if specified, but the elements themselves are not copied.
54 * If the elements should be duplicated to avoid confusion with another
55 * list, the Lst_Duplicate function should be called first.
56 * If LST_CONCLINK is specified, the second list is destroyed since
57 * its pointers have been corrupted and the list is no longer useable.
60 * SUCCESS if all went well. FAILURE otherwise.
63 * New elements are created and appended the the first list.
64 *-----------------------------------------------------------------------
67 Lst_Concat (l1, l2, flags)
68 Lst l1; /* The list to which l2 is to be appended */
69 Lst l2; /* The list to append to l1 */
70 int flags; /* LST_CONCNEW if LstNode's should be duplicated
71 * LST_CONCLINK if should just be relinked */
73 register ListNode ln; /* original LstNode */
74 register ListNode nln; /* new LstNode */
75 register ListNode last; /* the last element in the list. Keeps
76 * bookkeeping until the end */
77 register List list1 = (List)l1;
78 register List list2 = (List)l2;
80 if (!LstValid (l1) || !LstValid (l2)) {
84 if (flags == LST_CONCLINK) {
85 if (list2->firstPtr != NilListNode) {
87 * We set the nextPtr of the
88 * last element of list two to be NIL to make the loop easier and
89 * so we don't need an extra case should the first list turn
90 * out to be non-circular -- the final element will already point
91 * to NIL space and the first element will be untouched if it
92 * existed before and will also point to NIL space if it didn't.
94 list2->lastPtr->nextPtr = NilListNode;
96 * So long as the second list isn't empty, we just link the
97 * first element of the second list to the last element of the
98 * first list. If the first list isn't empty, we then link the
99 * last element of the list to the first element of the second list
100 * The last element of the second list, if it exists, then becomes
101 * the last element of the first list.
103 list2->firstPtr->prevPtr = list1->lastPtr;
104 if (list1->lastPtr != NilListNode) {
105 list1->lastPtr->nextPtr = list2->firstPtr;
107 list1->firstPtr = list2->firstPtr;
109 list1->lastPtr = list2->lastPtr;
111 if (list1->isCirc && list1->firstPtr != NilListNode) {
113 * If the first list is supposed to be circular and it is (now)
114 * non-empty, we must make sure it's circular by linking the
115 * first element to the last and vice versa
117 list1->firstPtr->prevPtr = list1->lastPtr;
118 list1->lastPtr->nextPtr = list1->firstPtr;
121 } else if (list2->firstPtr != NilListNode) {
123 * We set the nextPtr of the last element of list 2 to be nil to make
124 * the loop less difficult. The loop simply goes through the entire
125 * second list creating new LstNodes and filling in the nextPtr, and
126 * prevPtr to fit into l1 and its datum field from the
127 * datum field of the corresponding element in l2. The 'last' node
128 * follows the last of the new nodes along until the entire l2 has
129 * been appended. Only then does the bookkeeping catch up with the
130 * changes. During the first iteration of the loop, if 'last' is nil,
131 * the first list must have been empty so the newly-created node is
132 * made the first node of the list.
134 list2->lastPtr->nextPtr = NilListNode;
135 for (last = list1->lastPtr, ln = list2->firstPtr;
139 PAlloc (nln, ListNode);
140 nln->datum = ln->datum;
141 if (last != NilListNode) {
144 list1->firstPtr = nln;
147 nln->flags = nln->useCount = 0;
152 * Finish bookkeeping. The last new element becomes the last element
155 list1->lastPtr = last;
158 * The circularity of both list one and list two must be corrected
159 * for -- list one because of the new nodes added to it; list two
160 * because of the alteration of list2->lastPtr's nextPtr to ease the
164 list1->lastPtr->nextPtr = list1->firstPtr;
165 list1->firstPtr->prevPtr = list1->lastPtr;
167 last->nextPtr = NilListNode;
171 list2->lastPtr->nextPtr = list2->firstPtr;