libkern/i386/OSAtomic.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25  /*
  26  * Copyright (c) 1999 Apple Computer, Inc.
  27  *
  28  *
  29  * HISTORY
  30  *
  31  * wgulland  23 Jul 99 - Bogus implementation!
  32  */
  33 #include <libkern/OSAtomic.h>
  34
  35 #warning Bogus OSCompareAndSwap() for i386
  36 int OSCompareAndSwap( UInt32 oldVal,
  37         UInt32 newVal, UInt32 * addr )
  38 {
  39     /*
  40      * This should be
  41      * EAX = oldVal
  42      * Lock:CMPXCHG addr, newVal
  43      * But I don't know how to write that.
  44      */
  45     int ok;
  46     if( (ok = (oldVal == *addr)))
  47         *addr = newVal;
  48     return( ok );
  49 }
  50