release 2.1 of pmake

[unix-history] / usr / src / usr.bin / make / lst.lib / lstRemove.c

/*-
* LstRemove.c --
*      Remove an element from a list
*
* Copyright (c) 1988 by University of California Regents
*
* Permission to use, copy, modify, and distribute this
* software and its documentation for any purpose and without
* fee is hereby granted, provided that the above copyright
* notice appears in all copies.  Neither the University of California nor
* Adam de Boor makes any representations about the suitability of this
* software for any purpose.  It is provided "as is" without
* express or implied warranty.
*/
#ifndef lint
static char *rcsid =
"$Id: lstRemove.c,v 1.7 89/06/13 15:01:51 adam Exp $ SPRITE (Berkeley)";
#endif lint

#include        "lstInt.h"

/*-
*-----------------------------------------------------------------------
* Lst_Remove --
*      Remove the given node from the given list.
*
* Results:
*      SUCCESS or FAILURE.
*
* Side Effects:
*      The list's firstPtr will be set to NilListNode if ln is the last
*      node on the list. firsPtr and lastPtr will be altered if ln is
*      either the first or last node, respectively, on the list.
*
*-----------------------------------------------------------------------
*/
ReturnStatus
Lst_Remove (l, ln)
   Lst                 l;
   LstNode             ln;
{
   register List       list = (List) l;
   register ListNode   lNode = (ListNode) ln;

   if (!LstValid (l) ||
       !LstNodeValid (ln, l)) {
           return (FAILURE);
   }
   
   /*
    * unlink it from the list
    */
   if (lNode->nextPtr != NilListNode) {
       lNode->nextPtr->prevPtr = lNode->prevPtr;
   }
   if (lNode->prevPtr != NilListNode) {
       lNode->prevPtr->nextPtr = lNode->nextPtr;
   }
   
   /*
    * if either the firstPtr or lastPtr of the list point to this node,
    * adjust them accordingly
    */
   if (list->firstPtr == lNode) {
       list->firstPtr = lNode->nextPtr;
   }
   if (list->lastPtr == lNode) {
       list->lastPtr = lNode->prevPtr;
   }

   /*
    * Sequential access stuff. If the node we're removing is the current
    * node in the list, reset the current node to the previous one. If the
    * previous one was non-existent (prevPtr == NilListNode), we set the
    * end to be Unknown, since it is.
    */
   if (list->isOpen && (list->curPtr == lNode)) {
       list->curPtr = list->prevPtr;
       if (list->curPtr == NilListNode) {
           list->atEnd = Unknown;
       }
   }

   /*
    * the only way firstPtr can still point to ln is if ln is the last
    * node on the list (the list is circular, so lNode->nextptr == lNode in
    * this case). The list is, therefore, empty and is marked as such
    */
   if (list->firstPtr == lNode) {
       list->firstPtr = NilListNode;
   }
   
   /*
    * note that the datum is unmolested. The caller must free it as
    * necessary and as expected.
    */
   if (lNode->useCount == 0) {
       free ((Address)ln);
   } else {
       lNode->flags |= LN_DELETED;
   }
   
   return (SUCCESS);
}