FreeBSD/Linux Kernel Cross Reference
sys/kern/queue.c

     /* 
      * Mach Operating System
      * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
      * All Rights Reserved.
      * 
      * Permission to use, copy, modify and distribute this software and its
      * documentation is hereby granted, provided that both the copyright
      * notice and this permission notice appear in all copies of the
      * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     * 
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
     * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     * 
     * Carnegie Mellon requests users of this software to return to
     * 
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     * 
     * any improvements or extensions that they make and grant Carnegie Mellon
     * the rights to redistribute these changes.
     */
    /*
     * HISTORY
     * $Log:        queue.c,v $
     * Revision 2.8  93/03/09  10:55:20  danner
     *      Fixed remque not to typecast. ANSI C.
     *      [93/03/05            af]
     * 
     * Revision 2.7  93/01/27  09:35:03  danner
     *      Remove ifdef sun around insque and remque.
     *      [93/01/25            danner]
     * 
     * Revision 2.6  92/08/03  17:38:50  jfriedl
     *      removed silly prototypes
     *      [92/08/02            jfriedl]
     * 
     * Revision 2.5  92/05/21  17:15:19  jfriedl
     *      Added void to fcns that still needed it.
     *      [92/05/20            jfriedl]
     * 
     * Revision 2.4  91/05/14  16:45:45  mrt
     *      Correcting copyright
     * 
     * Revision 2.3  91/05/08  12:48:22  dbg
     *      Compile queue routines on vax.
     *      [91/03/26            dbg]
     * 
     * Revision 2.2  91/02/05  17:28:38  mrt
     *      Changed to new Mach copyright
     *      [91/02/01  16:16:22  mrt]
     * 
     * Revision 2.1  89/08/03  15:51:47  rwd
     * Created.
     * 
     * 17-Mar-87  David Golub (dbg) at Carnegie-Mellon University
     *      Created from routines written by David L. Black.
     *
     */ 
    
    /*
     *      Routines to implement queue package.
     */
    
    #include <kern/queue.h>
    
    
    
    /*
     *      Insert element at head of queue.
     */
    void enqueue_head(
            register queue_t        que,
            register queue_entry_t  elt)
    {
            elt->next = que->next;
            elt->prev = que;
            elt->next->prev = elt;
            que->next = elt;
    }
    
    /*
     *      Insert element at tail of queue.
     */
    void enqueue_tail(
            register queue_t        que,
            register queue_entry_t  elt)
    {
            elt->next = que;
            elt->prev = que->prev;
            elt->prev->next = elt;
            que->prev = elt;
    }
    
    /*
     *      Remove and return element at head of queue.
    */
   queue_entry_t dequeue_head(
           register queue_t        que)
   {
           register queue_entry_t  elt;
   
           if (que->next == que)
                   return((queue_entry_t)0);
   
           elt = que->next;
           elt->next->prev = que;
           que->next = elt->next;
           return(elt);
   }
   
   /*
    *      Remove and return element at tail of queue.
    */
   queue_entry_t dequeue_tail(
           register queue_t        que)
   {
           register queue_entry_t  elt;
   
           if (que->prev == que)
                   return((queue_entry_t)0);
   
           elt = que->prev;
           elt->prev->next = que;
           que->prev = elt->prev;
           return(elt);
   }
   
   /*
    *      Remove arbitrary element from queue.
    *      Does not check whether element is on queue - the world
    *      will go haywire if it isn't.
    */
   
   /*ARGSUSED*/
   void remqueue(
           queue_t                 que,
           register queue_entry_t  elt)
   {
           elt->next->prev = elt->prev;
           elt->prev->next = elt->next;
   }
   
   /*
    *      Routines to directly imitate the VAX hardware queue
    *      package.
    */
   void insque(
           register struct queue_entry *entry,
           register struct queue_entry *pred)
   {
           entry->next = pred->next;
           entry->prev = pred;
           (pred->next)->prev = entry;
           pred->next = entry;
   }
   
   struct queue_entry
   *remque(
           register struct queue_entry *elt)
   {
           (elt->next)->prev = elt->prev;
           (elt->prev)->next = elt->next;
           return(elt);
   }
   

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