1 /*
  2  * Copyright (c) 2000, 2025, 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 import java.io.FileDescriptor;
 29 import java.io.IOException;
 30 import jdk.internal.access.JavaIOFileDescriptorAccess;
 31 import jdk.internal.access.SharedSecrets;
 32 
 33 /**
 34  * Allows different platforms to call different native methods
 35  * for read and write operations.
 36  */
 37 
 38 abstract class NativeDispatcher {
 39     private static final JavaIOFileDescriptorAccess JIOFDA = SharedSecrets.getJavaIOFileDescriptorAccess();
 40 
 41     abstract int read(FileDescriptor fd, long address, int len)
 42         throws IOException;
 43 
 44     /**
 45      * Returns {@code true} if pread/pwrite needs to be synchronized with
 46      * position sensitive methods.
 47      */
 48     boolean needsPositionLock() {
 49         return false;
 50     }
 51 
 52     int pread(FileDescriptor fd, long address, int len, long position)
 53         throws IOException
 54     {
 55         throw new IOException("Operation Unsupported");
 56     }
 57 
 58     abstract long readv(FileDescriptor fd, long address, int len)
 59         throws IOException;
 60 
 61     abstract int write(FileDescriptor fd, long address, int len)
 62         throws IOException;
 63 
 64     int pwrite(FileDescriptor fd, long address, int len, long position)
 65         throws IOException
 66     {
 67         throw new IOException("Operation Unsupported");
 68     }
 69 
 70     abstract long writev(FileDescriptor fd, long address, int len)
 71         throws IOException;
 72 
 73     abstract void close(FileDescriptor fd) throws IOException;
 74 
 75     /**
 76      * Prepare the given file descriptor for closing. If a virtual thread is blocked
 77      * on the file descriptor then it is unparked so that it stops polling. On Unix systems,
 78      * if a platform thread is blocked on the file descriptor then the file descriptor is
 79      * dup'ed to a special fd and the thread signalled so that the syscall fails with EINTR.
 80      */
 81     final void preClose(FileDescriptor fd, long reader, long writer) throws IOException {
 82         if (NativeThread.isVirtualThread(reader) || NativeThread.isVirtualThread(writer)) {
 83             int fdVal = JIOFDA.get(fd);
 84             Poller.stopPoll(fdVal);
 85         }
 86         if (NativeThread.isNativeThread(reader) || NativeThread.isNativeThread(writer)) {
 87             implPreClose(fd, reader, writer);
 88         }
 89     }
 90 
 91     /**
 92      * This method does nothing by default. On Unix systems the file descriptor is dup'ed
 93      * to a special fd and native threads signalled.
 94      */
 95 
 96     void implPreClose(FileDescriptor fd, long reader, long writer) throws IOException {
 97         // Do nothing by default; this is only needed on Unix
 98     }
 99 
100     /**
101      * Duplicates a file descriptor.
102      * @param fd1 the file descriptor to duplicate
103      * @param fd2 the new file descriptor, the socket or file that it is connected
104      *            to will be closed by this method
105      */
106     void dup(FileDescriptor fd1, FileDescriptor fd2) throws IOException {
107         throw new UnsupportedOperationException();
108     }
109 }