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

   1 /*      $NetBSD: lstNext.c,v 1.12 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: lstNext.c,v 1.12 2008/12/13 15:19:29 dsl Exp $";
  37 #else
  38 #include <sys/cdefs.h>
  39 #ifndef lint
  40 #if 0
  41 static char sccsid[] = "@(#)lstNext.c   8.1 (Berkeley) 6/6/93";
  42 #else
  43 __RCSID("$NetBSD: lstNext.c,v 1.12 2008/12/13 15:19:29 dsl Exp $");
  44 #endif
  45 #endif /* not lint */
  46 #endif
  47
  48 /*-
  49  * LstNext.c --
  50  *      Return the next node for a list.
  51  *      The sequential functions access the list in a slightly different way.
  52  *      CurPtr points to their idea of the current node in the list and they
  53  *      access the list based on it. Because the list is circular, Lst_Next
  54  *      and Lst_Prev will go around the list forever. Lst_IsAtEnd must be
  55  *      used to determine when to stop.
  56  */
  57
  58 #include        "lstInt.h"
  59
  60 /*-
  61  *-----------------------------------------------------------------------
  62  * Lst_Next --
  63  *      Return the next node for the given list.
  64  *
  65  * Results:
  66  *      The next node or NULL if the list has yet to be opened. Also
  67  *      if the list is non-circular and the end has been reached, NULL
  68  *      is returned.
  69  *
  70  * Side Effects:
  71  *      the curPtr field is updated.
  72  *
  73  *-----------------------------------------------------------------------
  74  */
  75 LstNode
  76 Lst_Next(Lst l)
  77 {
  78     ListNode    tln;
  79     List        list = l;
  80
  81     if ((LstValid (l) == FALSE) ||
  82         (list->isOpen == FALSE)) {
  83             return NULL;
  84     }
  85
  86     list->prevPtr = list->curPtr;
  87
  88     if (list->curPtr == NULL) {
  89         if (list->atEnd == Unknown) {
  90             /*
  91              * If we're just starting out, atEnd will be Unknown.
  92              * Then we want to start this thing off in the right
  93              * direction -- at the start with atEnd being Middle.
  94              */
  95             list->curPtr = tln = list->firstPtr;
  96             list->atEnd = Middle;
  97         } else {
  98             tln = NULL;
  99             list->atEnd = Tail;
 100         }
 101     } else {
 102         tln = list->curPtr->nextPtr;
 103         list->curPtr = tln;
 104
 105         if (tln == list->firstPtr || tln == NULL) {
 106             /*
 107              * If back at the front, then we've hit the end...
 108              */
 109             list->atEnd = Tail;
 110         } else {
 111             /*
 112              * Reset to Middle if gone past first.
 113              */
 114             list->atEnd = Middle;
 115         }
 116     }
 117
 118     return (tln);
 119 }
 120