reactos/lib/intrlck/i386/compareexchange.c

   1 /*
   2  * PROJECT:     ReactOS system libraries
   3  * LICENSE:     GPL - See COPYING in the top level directory
   4  * FILE:        lib/intrlck/i386/compareexchange.c
   5  * PURPOSE:     Inter lock compare exchanges
   6  * PROGRAMMERS: Copyright 1995 Martin von Loewis
   7  *              Copyright 1997 Onno Hovers
   8  */
   9
  10 /************************************************************************
  11  *           InterlockedCompareExchange
  12  *
  13  * Atomically compares Destination and Comperand, and if found equal exchanges
  14  * the value of Destination with Exchange
  15  *
  16  * RETURNS
  17  *      Prior value of value pointed to by Destination
  18  */
  19
  20 /*
  21  * LONG NTAPI InterlockedCompareExchange(LPLONG Destination, LONG Exchange, LONG Comperand)
  22  */
  23
  24 #include <windows.h>
  25 LONG
  26 NTAPI
  27 InterlockedCompareExchange(
  28         IN OUT LONG volatile *Destination,
  29         LONG Exchange,
  30         LONG Comperand)
  31 {
  32         LONG ret;
  33         __asm__ __volatile__(
  34                 "lock; cmpxchgl %2,(%1)"
  35                 : "=a" (ret) : "r" (Destination), "r" (Exchange), "0" (Comperand) : "memory" );
  36         return ret;
  37 }