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

   1 /*      $NetBSD: lstDeQueue.c,v 1.13 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: lstDeQueue.c,v 1.13 2008/12/13 15:19:29 dsl Exp $";
  37 #else
  38 #include <sys/cdefs.h>
  39 #ifndef lint
  40 #if 0
  41 static char sccsid[] = "@(#)lstDeQueue.c        8.1 (Berkeley) 6/6/93";
  42 #else
  43 __RCSID("$NetBSD: lstDeQueue.c,v 1.13 2008/12/13 15:19:29 dsl Exp $");
  44 #endif
  45 #endif /* not lint */
  46 #endif
  47
  48 /*-
  49  * LstDeQueue.c --
  50  *      Remove the node and return its datum from the head of the list
  51  */
  52
  53 #include        "lstInt.h"
  54
  55 /*-
  56  *-----------------------------------------------------------------------
  57  * Lst_DeQueue --
  58  *      Remove and return the datum at the head of the given list.
  59  *
  60  * Results:
  61  *      The datum in the node at the head or NULL if the list
  62  *      is empty.
  63  *
  64  * Side Effects:
  65  *      The head node is removed from the list.
  66  *
  67  *-----------------------------------------------------------------------
  68  */
  69 void *
  70 Lst_DeQueue(Lst l)
  71 {
  72     void *rd;
  73     ListNode    tln;
  74
  75     tln = Lst_First(l);
  76     if (tln == NULL) {
  77         return NULL;
  78     }
  79
  80     rd = tln->datum;
  81     if (Lst_Remove(l, tln) == FAILURE) {
  82         return NULL;
  83     } else {
  84         return (rd);
  85     }
  86 }
  87