1 /*
 2  * Copyright (c) 2002, 2023, 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.  Oracle designates this
 8  * particular file as subject to the "Classpath" exception as provided
 9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
18  * 2 along with this work; if not, write to the Free Software Foundation,
19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20  *
21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22  * or visit www.oracle.com if you need additional information or have any
23  * questions.
24  */
25 
26 package sun.nio.ch;
27 
28 
29 // Signalling operations on native threads
30 
31 public class NativeThread {
32     private static final long VIRTUAL_THREAD_ID = -1L;
33 
34     /**
35      * Returns the id of the current native thread if the platform can signal
36      * native threads, 0 if the platform can not signal native threads, or
37      * -1L if the current thread is a virtual thread.
38      */
39     public static long current() {
40         if (Thread.currentThread().isVirtual()) {
41             return VIRTUAL_THREAD_ID;
42         } else {
43             // no support for signalling threads on Windows
44             return 0;
45         }
46     }
47 
48     /**
49      * Signals the given native thread.
50      *
51      * @throws IllegalArgumentException if tid is not a token to a native thread
52      */
53     static void signal(long tid) {
54         throw new UnsupportedOperationException();
55     }
56 
57     /**
58      * Returns true the tid is the id of a native thread.
59      */
60     static boolean isNativeThread(long tid) {
61         return false;
62     }
63 
64     /**
65      * Returns true if tid is -1L.
66      * @see #current()
67      */
68     static boolean isVirtualThread(long tid) {
69         return (tid == VIRTUAL_THREAD_ID);
70     }
71 }