libkern/i386/OSAtomic.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22  /*
  23  * Copyright (c) 1999 Apple Computer, Inc.
  24  *
  25  *
  26  * HISTORY
  27  *
  28  * wgulland  23 Jul 99 - Bogus implementation!
  29  */
  30 #include <libkern/OSAtomic.h>
  31
  32 #warning Bogus OSCompareAndSwap() for i386
  33 int OSCompareAndSwap( UInt32 oldVal,
  34         UInt32 newVal, UInt32 * addr )
  35 {
  36     /*
  37      * This should be
  38      * EAX = oldVal
  39      * Lock:CMPXCHG addr, newVal
  40      * But I don't know how to write that.
  41      */
  42     int ok;
  43     if( (ok = (oldVal == *addr)))
  44         *addr = newVal;
  45     return( ok );
  46 }
  47