usr.bin/make/lst.lib/lstConcat.c

   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
  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