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Annotation of 43BSDReno/usr.bin/make/lst.lib/lstNext.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
                      3:  * All rights reserved.
                      4:  *
                      5:  * This code is derived from software contributed to Berkeley by
                      6:  * Adam de Boor.
                      7:  *
                      8:  * Redistribution and use in source and binary forms are permitted
                      9:  * provided that: (1) source distributions retain this entire copyright
                     10:  * notice and comment, and (2) distributions including binaries display
                     11:  * the following acknowledgement:  ``This product includes software
                     12:  * developed by the University of California, Berkeley and its contributors''
                     13:  * in the documentation or other materials provided with the distribution
                     14:  * and in all advertising materials mentioning features or use of this
                     15:  * software. Neither the name of the University nor the names of its
                     16:  * contributors may be used to endorse or promote products derived
                     17:  * from this software without specific prior written permission.
                     18:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     19:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     20:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     21:  */
                     22: 
                     23: #ifndef lint
                     24: static char sccsid[] = "@(#)lstNext.c  5.3 (Berkeley) 6/1/90";
                     25: #endif /* not lint */
                     26: 
                     27: /*-
                     28:  * LstNext.c --
                     29:  *     Return the next node for a list.
                     30:  *     The sequential functions access the list in a slightly different way.
                     31:  *     CurPtr points to their idea of the current node in the list and they
                     32:  *     access the list based on it. Because the list is circular, Lst_Next
                     33:  *     and Lst_Prev will go around the list forever. Lst_IsAtEnd must be
                     34:  *     used to determine when to stop.
                     35:  */
                     36: 
                     37: #include       "lstInt.h"
                     38: 
                     39: /*-
                     40:  *-----------------------------------------------------------------------
                     41:  * Lst_Next --
                     42:  *     Return the next node for the given list.
                     43:  *
                     44:  * Results:
                     45:  *     The next node or NILLNODE if the list has yet to be opened. Also
                     46:  *     if the list is non-circular and the end has been reached, NILLNODE
                     47:  *     is returned.
                     48:  *
                     49:  * Side Effects:
                     50:  *     the curPtr field is updated.
                     51:  *
                     52:  *-----------------------------------------------------------------------
                     53:  */
                     54: LstNode
                     55: Lst_Next (l)
                     56:     Lst                  l;
                     57: {
                     58:     register ListNode  tln;
                     59:     register List      list = (List)l;
                     60:     
                     61:     if ((LstValid (l) == FALSE) ||
                     62:        (list->isOpen == FALSE)) {
                     63:            return (NILLNODE);
                     64:     }
                     65:     
                     66:     list->prevPtr = list->curPtr;
                     67:     
                     68:     if (list->curPtr == NilListNode) {
                     69:        if (list->atEnd == Unknown) {
                     70:            /*
                     71:             * If we're just starting out, atEnd will be Unknown.
                     72:             * Then we want to start this thing off in the right
                     73:             * direction -- at the start with atEnd being Middle.
                     74:             */
                     75:            list->curPtr = tln = list->firstPtr;
                     76:            list->atEnd = Middle;
                     77:        } else {
                     78:            tln = NilListNode;
                     79:            list->atEnd = Tail;
                     80:        }
                     81:     } else {
                     82:        tln = list->curPtr->nextPtr;
                     83:        list->curPtr = tln;
                     84: 
                     85:        if (tln == list->firstPtr || tln == NilListNode) {
                     86:            /*
                     87:             * If back at the front, then we've hit the end...
                     88:             */
                     89:            list->atEnd = Tail;
                     90:        } else {
                     91:            /*
                     92:             * Reset to Middle if gone past first.
                     93:             */
                     94:            list->atEnd = Middle;
                     95:        }
                     96:     }
                     97:     
                     98:     return ((LstNode)tln);
                     99: }
                    100: 

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