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 POLLIN polling.
 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 POLLOUT polling.
 89      * @param subPoller true to create a sub-poller
 90      */
 91     abstract Poller writePoller(boolean subPoller) throws IOException;
 92 
 93     /**
 94      * Returns true if read pollers support read ops in addition to POLLIN polling.
 95      * @implSpec The default implementation returns false.
 96      */
 97     boolean supportReadOps() {
 98         return false;
 99     }
100 
101     /**
102      * Returns true if write pollers support write ops in addition to POLLOUT polling.
103      * @implSpec The default implementation returns false.
104      */
105     boolean supportWriteOps() {
106         return false;
107     }
108 }