+/*-
+ * listConcat.c --
+ * Function to concatentate two lists.
+ *
+ * Copyright (c) 1988 by the Regents of the University of California
+ *
+ * Permission to use, copy, modify, and distribute this
+ * software and its documentation for any purpose and without
+ * fee is hereby granted, provided that the above copyright
+ * notice appears in all copies. Neither the University of California nor
+ * Adam de Boor makes any representations about the suitability of this
+ * software for any purpose. It is provided "as is" without
+ * express or implied warranty.
+ *
+ */
+#ifndef lint
+static char *rcsid =
+"$Id: lstConcat.c,v 1.6 89/07/06 12:50:04 adam Exp $ SPRITE (Berkeley)";
+#endif lint
+
+#include "lstInt.h"
+
+/*-
+ *-----------------------------------------------------------------------
+ * Lst_Concat --
+ * Concatenate two lists. New elements are created to hold the data
+ * elements, if specified, but the elements themselves are not copied.
+ * If the elements should be duplicated to avoid confusion with another
+ * list, the Lst_Duplicate function should be called first.
+ * If LST_CONCLINK is specified, the second list is destroyed since
+ * its pointers have been corrupted and the list is no longer useable.
+ *
+ * Results:
+ * SUCCESS if all went well. FAILURE otherwise.
+ *
+ * Side Effects:
+ * New elements are created and appended the the first list.
+ *-----------------------------------------------------------------------
+ */
+ReturnStatus
+Lst_Concat (l1, l2, flags)
+ Lst l1; /* The list to which l2 is to be appended */
+ Lst l2; /* The list to append to l1 */
+ int flags; /* LST_CONCNEW if LstNode's should be duplicated
+ * LST_CONCLINK if should just be relinked */
+{
+ register ListNode ln; /* original LstNode */
+ register ListNode nln; /* new LstNode */
+ register ListNode last; /* the last element in the list. Keeps
+ * bookkeeping until the end */
+ register List list1 = (List)l1;
+ register List list2 = (List)l2;
+
+ if (!LstValid (l1) || !LstValid (l2)) {
+ return (FAILURE);
+ }
+
+ if (flags == LST_CONCLINK) {
+ if (list2->firstPtr != NilListNode) {
+ /*
+ * We set the nextPtr of the
+ * last element of list two to be NIL to make the loop easier and
+ * so we don't need an extra case should the first list turn
+ * out to be non-circular -- the final element will already point
+ * to NIL space and the first element will be untouched if it
+ * existed before and will also point to NIL space if it didn't.
+ */
+ list2->lastPtr->nextPtr = NilListNode;
+ /*
+ * So long as the second list isn't empty, we just link the
+ * first element of the second list to the last element of the
+ * first list. If the first list isn't empty, we then link the
+ * last element of the list to the first element of the second list
+ * The last element of the second list, if it exists, then becomes
+ * the last element of the first list.
+ */
+ list2->firstPtr->prevPtr = list1->lastPtr;
+ if (list1->lastPtr != NilListNode) {
+ list1->lastPtr->nextPtr = list2->firstPtr;
+ }
+ list1->lastPtr = list2->lastPtr;
+ }
+ if (list1->isCirc && list1->firstPtr != NilListNode) {
+ /*
+ * If the first list is supposed to be circular and it is (now)
+ * non-empty, we must make sure it's circular by linking the
+ * first element to the last and vice versa
+ */
+ list1->firstPtr->prevPtr = list1->lastPtr;
+ list1->lastPtr->nextPtr = list1->firstPtr;
+ }
+ free ((Address)l2);
+ } else if (list2->firstPtr != NilListNode) {
+ /*
+ * We set the nextPtr of the last element of list 2 to be nil to make
+ * the loop less difficult. The loop simply goes through the entire
+ * second list creating new LstNodes and filling in the nextPtr, and
+ * prevPtr to fit into l1 and its datum field from the
+ * datum field of the corresponding element in l2. The 'last' node
+ * follows the last of the new nodes along until the entire l2 has
+ * been appended. Only then does the bookkeeping catch up with the
+ * changes. During the first iteration of the loop, if 'last' is nil,
+ * the first list must have been empty so the newly-created node is
+ * made the first node of the list.
+ */
+ list2->lastPtr->nextPtr = NilListNode;
+ for (last = list1->lastPtr, ln = list2->firstPtr;
+ ln != NilListNode;
+ ln = ln->nextPtr)
+ {
+ PAlloc (nln, ListNode);
+ nln->datum = ln->datum;
+ if (last != NilListNode) {
+ last->nextPtr = nln;
+ } else {
+ list1->firstPtr = nln;
+ }
+ nln->prevPtr = last;
+ nln->flags = nln->useCount = 0;
+ last = nln;
+ }
+
+ /*
+ * Finish bookkeeping. The last new element becomes the last element
+ * of list one.
+ */
+ list1->lastPtr = last;
+
+ /*
+ * The circularity of both list one and list two must be corrected
+ * for -- list one because of the new nodes added to it; list two
+ * because of the alteration of list2->lastPtr's nextPtr to ease the
+ * above for loop.
+ */
+ if (list1->isCirc) {
+ list1->lastPtr->nextPtr = list1->firstPtr;
+ list1->firstPtr->prevPtr = list1->lastPtr;
+ } else {
+ last->nextPtr = NilListNode;
+ }
+
+ if (list2->isCirc) {
+ list2->lastPtr->nextPtr = list2->firstPtr;
+ }
+ }
+
+ return (SUCCESS);
+}
+
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