1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 package org.chromium.mojo.system;
6 
7 import org.chromium.mojo.system.Core.HandleSignals;
8 
9 /**
10  * A class which implements the {@link AsyncWaiter} allows asynchronously waiting on a background
11  * thread.
12  */
13 public interface AsyncWaiter {
14 
15     /**
16      * Allows cancellation of an asyncWait operation.
17      */
18     interface Cancellable {
19         /**
20          * Cancels an asyncWait operation. Has no effect if the operation has already been canceled
21          * or the callback has already been called.
22          * <p>
23          * Must be called from the same thread as {@link AsyncWaiter#asyncWait} was called from.
24          */
cancel()25         void cancel();
26     }
27 
28     /**
29      * Callback passed to {@link AsyncWaiter#asyncWait}.
30      */
31     public interface Callback {
32         /**
33          * Called when the handle is ready.
34          */
onResult(int result)35         public void onResult(int result);
36 
37         /**
38          * Called when an error occurred while waiting.
39          */
onError(MojoException exception)40         public void onError(MojoException exception);
41     }
42 
43     /**
44      * Asynchronously call wait on a background thread. The given {@link Callback} will be notified
45      * of the result of the wait on the same thread as asyncWait was called.
46      *
47      * @return a {@link Cancellable} object that can be used to cancel waiting. The cancellable
48      *         should only be used on the current thread, and becomes invalid once the callback has
49      *         been notified.
50      */
asyncWait(Handle handle, HandleSignals signals, long deadline, Callback callback)51     Cancellable asyncWait(Handle handle, HandleSignals signals, long deadline, Callback callback);
52 
53 }
54