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
22  * or visit www.oracle.com if you need additional information or have any
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 final Poller.Mode mode;
34 
35     PollerProvider(Poller.Mode mode) {
36         this.mode = mode;
37     }
38 
39     final Poller.Mode pollerMode() {
40         return mode;
41     }
42 
43     /**
44      * Creates a PollerProvider that uses its preferred/default poller mode.
45      */
46     static PollerProvider createProvider() {
47         return new DefaultPollerProvider();
48     }
49 
50     /**
51      * Creates a PollerProvider that uses the given poller mode.
52      */
53     static PollerProvider createProvider(Poller.Mode mode) {
54         return new DefaultPollerProvider(mode);
55     }
56 
57     /**
58      * Default number of read pollers. The count must be a power of 2.
59      * @implSpec The default implementation returns 1.
60      */
61     int defaultReadPollers() {
62         return 1;
63     }
64 
65     /**
66      * Default number of write pollers. The count must be a power of 2.
67      * @implSpec The default implementation returns 1.
68      */
69     int defaultWritePollers() {
70         return 1;
71     }
72 
73     /**
74      * Maps a file descriptor to an index from 0 to {@code toIndex}.
75      * @implSpec The default implementation is good for Unix file descriptors.
76      */
77     int fdValToIndex(int fdVal, int toIndex) {
78         return fdVal & (toIndex - 1);
79     }
80 
81     /**
82      * Creates a Poller for read ops.
83      * @param subPoller true to create a sub-poller
84      */
85     abstract Poller readPoller(boolean subPoller) throws IOException;
86 
87     /**
88      * Creates a Poller for write ops.
89      * @param subPoller true to create a sub-poller
90      */
91     abstract Poller writePoller(boolean subPoller) throws IOException;
92 }