1 /*
 2  * Copyright (c) 2017, 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
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23  * questions.
24  */
25 package sun.nio.ch;
26 
27 import java.io.IOException;
28 
29 /**
30  * Provider class for Poller implementations.
31  */
32 abstract class PollerProvider {
33     private static final PollerProvider INSTANCE = new DefaultPollerProvider();
34 
35     PollerProvider() { }
36 
37     /**
38      * Returns the system-wide PollerProvider.
39      */
40     static PollerProvider provider() {
41         return INSTANCE;
42     }
43 
44     /**
45      * Returns the default poller mode.
46      * @implSpec The default implementation uses system threads.
47      */
48     Poller.Mode defaultPollerMode() {
49         return Poller.Mode.SYSTEM_THREADS;
50     }
51 
52     /**
53      * Default number of read pollers for the given mode. The count must be a power of 2.
54      * @implSpec The default implementation returns 1.
55      */
56     int defaultReadPollers(Poller.Mode mode) {
57         return 1;
58     }
59 
60     /**
61      * Default number of write pollers for the given mode. The count must be a power of 2.
62      * @implSpec The default implementation returns 1.
63      */
64     int defaultWritePollers(Poller.Mode mode) {
65         return 1;
66     }
67 
68     /**
69      * Maps a file descriptor to an index from 0 to {@code toIndex}.
70      * @implSpec The default implementation is good for Unix file descriptors.
71      */
72     int fdValToIndex(int fdVal, int toIndex) {
73         return fdVal & (toIndex - 1);
74     }
75 
76     /**
77      * Creates a Poller for read ops.
78      * @param subPoller true to create a sub-poller
79      */
80     abstract Poller readPoller(boolean subPoller) throws IOException;
81 
82     /**
83      * Creates a Poller for write ops.
84      * @param subPoller true to create a sub-poller
85      */
86     abstract Poller writePoller(boolean subPoller) throws IOException;
87 }