projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 44c1a173 WJ |
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, with or without | |
| 9 | * modification, are permitted provided that the following conditions | |
| 10 | * are met: | |
| 11 | * 1. Redistributions of source code must retain the above copyright | |
| 12 | * notice, this list of conditions and the following disclaimer. | |
| 13 | * 2. Redistributions in binary form must reproduce the above copyright | |
| 14 | * notice, this list of conditions and the following disclaimer in the | |
| 15 | * documentation and/or other materials provided with the distribution. | |
| 16 | * 3. All advertising materials mentioning features or use of this software | |
| 17 | * must display the following acknowledgement: | |
| 18 | * This product includes software developed by the University of | |
| 19 | * California, Berkeley and its contributors. | |
| 20 | * 4. Neither the name of the University nor the names of its contributors | |
| 21 | * may be used to endorse or promote products derived from this software | |
| 22 | * without specific prior written permission. | |
| 23 | * | |
| 24 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
| 25 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 26 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 27 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
| 28 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 29 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
| 30 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
| 31 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
| 32 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
| 33 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
| 34 | * SUCH DAMAGE. | |
| 35 | */ | |
| 36 | ||
| 37 | #ifndef lint | |
| 38 | static char sccsid[] = "@(#)lstNext.c 5.3 (Berkeley) 6/1/90"; | |
| 39 | #endif /* not lint */ | |
| 40 | ||
| 41 | /*- | |
| 42 | * LstNext.c -- | |
| 43 | * Return the next node for a list. | |
| 44 | * The sequential functions access the list in a slightly different way. | |
| 45 | * CurPtr points to their idea of the current node in the list and they | |
| 46 | * access the list based on it. Because the list is circular, Lst_Next | |
| 47 | * and Lst_Prev will go around the list forever. Lst_IsAtEnd must be | |
| 48 | * used to determine when to stop. | |
| 49 | */ | |
| 50 | ||
| 51 | #include "lstInt.h" | |
| 52 | ||
| 53 | /*- | |
| 54 | *----------------------------------------------------------------------- | |
| 55 | * Lst_Next -- | |
| 56 | * Return the next node for the given list. | |
| 57 | * | |
| 58 | * Results: | |
| 59 | * The next node or NILLNODE if the list has yet to be opened. Also | |
| 60 | * if the list is non-circular and the end has been reached, NILLNODE | |
| 61 | * is returned. | |
| 62 | * | |
| 63 | * Side Effects: | |
| 64 | * the curPtr field is updated. | |
| 65 | * | |
| 66 | *----------------------------------------------------------------------- | |
| 67 | */ | |
| 68 | LstNode | |
| 69 | Lst_Next (l) | |
| 70 | Lst l; | |
| 71 | { | |
| 72 | register ListNode tln; | |
| 73 | register List list = (List)l; | |
| 74 | ||
| 75 | if ((LstValid (l) == FALSE) || | |
| 76 | (list->isOpen == FALSE)) { | |
| 77 | return (NILLNODE); | |
| 78 | } | |
| 79 | ||
| 80 | list->prevPtr = list->curPtr; | |
| 81 | ||
| 82 | if (list->curPtr == NilListNode) { | |
| 83 | if (list->atEnd == Unknown) { | |
| 84 | /* | |
| 85 | * If we're just starting out, atEnd will be Unknown. | |
| 86 | * Then we want to start this thing off in the right | |
| 87 | * direction -- at the start with atEnd being Middle. | |
| 88 | */ | |
| 89 | list->curPtr = tln = list->firstPtr; | |
| 90 | list->atEnd = Middle; | |
| 91 | } else { | |
| 92 | tln = NilListNode; | |
| 93 | list->atEnd = Tail; | |
| 94 | } | |
| 95 | } else { | |
| 96 | tln = list->curPtr->nextPtr; | |
| 97 | list->curPtr = tln; | |
| 98 | ||
| 99 | if (tln == list->firstPtr || tln == NilListNode) { | |
| 100 | /* | |
| 101 | * If back at the front, then we've hit the end... | |
| 102 | */ | |
| 103 | list->atEnd = Tail; | |
| 104 | } else { | |
| 105 | /* | |
| 106 | * Reset to Middle if gone past first. | |
| 107 | */ | |
| 108 | list->atEnd = Middle; | |
| 109 | } | |
| 110 | } | |
| 111 | ||
| 112 | return ((LstNode)tln); | |
| 113 | } | |
| 114 |