libkern/i386/OSAtomic.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_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. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28  /*
  29  * Copyright (c) 1999 Apple Computer, Inc.
  30  *
  31  *
  32  * HISTORY
  33  *
  34  * wgulland  23 Jul 99 - Bogus implementation!
  35  */
  36 #include <libkern/OSAtomic.h>
  37
  38 #warning Bogus OSCompareAndSwap() for i386
  39 int OSCompareAndSwap( UInt32 oldVal,
  40         UInt32 newVal, UInt32 * addr )
  41 {
  42     /*
  43      * This should be
  44      * EAX = oldVal
  45      * Lock:CMPXCHG addr, newVal
  46      * But I don't know how to write that.
  47      */
  48     int ok;
  49     if( (ok = (oldVal == *addr)))
  50         *addr = newVal;
  51     return( ok );
  52 }
  53