source: trunk/src/kmk/lst.lib/lstConcat.c@ 19

/*
 * Copyright (c) 1988, 1989, 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Adam de Boor.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * @(#)lstConcat.c      8.1 (Berkeley) 6/6/93
 */

#ifndef lint
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/usr.bin/make/lst.lib/lstConcat.c,v 1.11 2002/10/09 02:00:22 jmallett Exp $");
#endif /* not lint */

/*-
 * listConcat.c --
 *      Function to concatentate two lists.
 */

#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 != NULL) {
            /*
             * We set the nextPtr of the
             * last element of list two to be NULL 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 NULL space and the first element will be untouched if it
             * existed before and will also point to NULL space if it didn't.
             */
            list2->lastPtr->nextPtr = NULL;
            /*
             * 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 != NULL) {
                list1->lastPtr->nextPtr = list2->firstPtr;
            } else {
                list1->firstPtr = list2->firstPtr;
            }
            list1->lastPtr = list2->lastPtr;
        }
        if (list1->isCirc && list1->firstPtr != NULL) {
            /*
             * 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 (l2);
    } else if (list2->firstPtr != NULL) {
        /*
         * We set the nextPtr of the last element of list 2 to be NULL 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 NULL,
         * the first list must have been empty so the newly-created node is
         * made the first node of the list.
         */
        list2->lastPtr->nextPtr = NULL;
        for (last = list1->lastPtr, ln = list2->firstPtr;
             ln != NULL;
             ln = ln->nextPtr)
        {
            PAlloc (nln, ListNode);
            nln->datum = ln->datum;
            if (last != NULL) {
                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 = NULL;
        }

        if (list2->isCirc) {
            list2->lastPtr->nextPtr = list2->firstPtr;
        }
    }

    return (SUCCESS);
}