libkern/i386/OSAtomic.c

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