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 
 31 /**
 32  * Allows different platforms to call different native methods
 33  * for read and write operations.
 34  */
 35 
 36 abstract class NativeDispatcher {
 37 
 38     abstract int read(FileDescriptor fd, long address, int len)
 39         throws IOException;
 40 
 41     /**
 42      * Returns {@code true} if pread/pwrite needs to be synchronized with
 43      * position sensitive methods.
 44      */
 45     boolean needsPositionLock() {
 46         return false;
 47     }
 48 
 49     int pread(FileDescriptor fd, long address, int len, long position)
 50         throws IOException
 51     {
 52         throw new IOException("Operation Unsupported");
 53     }
 54 
 55     abstract long readv(FileDescriptor fd, long address, int len)
 56         throws IOException;
 57 
 58     abstract int write(FileDescriptor fd, long address, int len)
 59         throws IOException;
 60 
 61     int pwrite(FileDescriptor fd, long address, int len, long position)
 62         throws IOException
 63     {
 64         throw new IOException("Operation Unsupported");
 65     }
 66 
 67     abstract long writev(FileDescriptor fd, long address, int len)
 68         throws IOException;
 69 
 70     abstract void close(FileDescriptor fd) throws IOException;
 71 
 72     /**
 73      * Prepare the given file descriptor for closing. If a virtual thread is blocked
 74      * on the file descriptor then it is unparked so that it stops polling. On Unix systems,
 75      * if a platform thread is blocked on the file descriptor then the file descriptor is
 76      * dup'ed to a special fd and the thread signalled so that the syscall fails with EINTR.
 77      */
 78     final void preClose(FileDescriptor fd, Thread reader, Thread writer) throws IOException {
 79         if (reader != null && reader.isVirtual()) {
 80             NativeThread.signal(reader);  // unparks virtual thread
 81             reader = null;
 82         }
 83         if (writer != null && writer.isVirtual()) {
 84             NativeThread.signal(writer);  // unparks virtual thread
 85             writer = null;
 86         }
 87         // dup2 and signal platform threads
 88         implPreClose(fd, reader, writer);
 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     void implPreClose(FileDescriptor fd, Thread reader, Thread writer) throws IOException {
 96         // Do nothing by default; this is only needed on Unix
 97     }
 98 
 99     /**
100      * Duplicates a file descriptor.
101      * @param fd1 the file descriptor to duplicate
102      * @param fd2 the new file descriptor, the socket or file that it is connected
103      *            to will be closed by this method
104      */
105     void dup(FileDescriptor fd1, FileDescriptor fd2) throws IOException {
106         throw new UnsupportedOperationException();
107     }
108 }