1/*
2 * Copyright (c) 2000, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25package sun.jvm.hotspot.utilities;
26
27/** <p> A two-way unbounded-length message queue useful for
28    communication between threads. Messages written on one side become
29    readable on the other in first-in, first-out order. This is an
30    interface to one of two "sides" of an underlying backend, for
31    example, the MessageQueueBackend. </p> */
32
33public interface MessageQueue {
34  /** This blocks until a message is available. Even if the thread is
35      interrupted while it is waiting, this will not return until a
36      message is written by the entity on the other side of the
37      queue. */
38  public Object readMessage();
39
40  /** This blocks for up to <code>millis</code> milliseconds until a
41      message is available. If no message becomes available within
42      this time period, or the thread is interrupted during the wait,
43      returns null. (This implies that passing the value null back and
44      forth is not distinguishable with this method.) Passing a value
45      of 0 for the <code>millis</code> argument causes this method to
46      return without blocking. The millis argument must be greater
47      than or equal to zero. */
48  public Object readMessageWithTimeout(long millis);
49
50  /** Write a message to the queue */
51  public void writeMessage(Object obj);
52}
53