usr/src/usr.bin/make/lst.lib/lstInsert.c

/*
 * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Adam de Boor.
 *
 * %sccs.include.redist.c%
 */

#ifndef lint
static char sccsid[] = "@(#)lstInsert.c 5.3 (Berkeley) %G%";
#endif /* not lint */

/*-
 * LstInsert.c --
 *      Insert a new datum before an old one
 */

#include        "lstInt.h"

/*-
 *-----------------------------------------------------------------------
 * Lst_Insert --
 *      Insert a new node with the given piece of data before the given
 *      node in the given list.
 *
 * Results:
 *      SUCCESS or FAILURE.
 *
 * Side Effects:
 *      the firstPtr field will be changed if ln is the first node in the
 *      list.
 *
 *-----------------------------------------------------------------------
 */
ReturnStatus
Lst_Insert (l, ln, d)
    Lst                 l;      /* list to manipulate */
    LstNode             ln;     /* node before which to insert d */
    ClientData          d;      /* datum to be inserted */
{
    register ListNode   nLNode; /* new lnode for d */
    register ListNode   lNode = (ListNode)ln;
    register List       list = (List)l;


    /*
     * check validity of arguments
     */
    if (LstValid (l) && (LstIsEmpty (l) && ln == NILLNODE))
        goto ok;

    if (!LstValid (l) || LstIsEmpty (l) || !LstNodeValid (ln, l)) {
        return (FAILURE);
    }

    ok:
    PAlloc (nLNode, ListNode);

    nLNode->datum = d;
    nLNode->useCount = nLNode->flags = 0;

    if (ln == NILLNODE) {
        if (list->isCirc) {
            nLNode->prevPtr = nLNode->nextPtr = nLNode;
        } else {
            nLNode->prevPtr = nLNode->nextPtr = NilListNode;
        }
        list->firstPtr = list->lastPtr = nLNode;
    } else {
        nLNode->prevPtr = lNode->prevPtr;
        nLNode->nextPtr = lNode;

        if (nLNode->prevPtr != NilListNode) {
            nLNode->prevPtr->nextPtr = nLNode;
        }
        lNode->prevPtr = nLNode;

        if (lNode == list->firstPtr) {
            list->firstPtr = nLNode;
        }
    }

    return (SUCCESS);
}