/*

 * Copyright 2001-2003 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

# include "incls/_precompiled.incl"

# include "incls/_atomic.cpp.incl"

jbyte Atomic::cmpxchg(jbyte exchange_value, volatile jbyte* dest, jbyte compare_value) {

  assert(sizeof(jbyte) == 1, "assumption.");

  uintptr_t dest_addr = (uintptr_t)dest;

  uintptr_t offset = dest_addr % sizeof(jint);

  volatile jint* dest_int = (volatile jint*)(dest_addr - offset);

  jint cur = *dest_int;

  jbyte* cur_as_bytes = (jbyte*)(&cur);

  jint new_val = cur;

  jbyte* new_val_as_bytes = (jbyte*)(&new_val);

  new_val_as_bytes[offset] = exchange_value;

  while (cur_as_bytes[offset] == compare_value) {

    jint res = cmpxchg(new_val, dest_int, cur);

    if (res == cur) break;

    cur = res;

    new_val = cur;

    new_val_as_bytes[offset] = exchange_value;

  }

  return cur_as_bytes[offset];

}