| /* |
| * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.io; |
| |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| /** |
| * Instances of the file descriptor class serve as an opaque handle |
| * to the underlying machine-specific structure representing an open |
| * file, an open socket, or another source or sink of bytes. The |
| * main practical use for a file descriptor is to create a |
| * <code>FileInputStream</code> or <code>FileOutputStream</code> to |
| * contain it. |
| * <p> |
| * Applications should not create their own file descriptors. |
| * |
| * @author Pavani Diwanji |
| * @see java.io.FileInputStream |
| * @see java.io.FileOutputStream |
| * @since JDK1.0 |
| */ |
| public final class FileDescriptor { |
| |
| private int fd; |
| |
| /** |
| * A counter for tracking the FIS/FOS/RAF instances that |
| * use this FileDescriptor. The FIS/FOS.finalize() will not release |
| * the FileDescriptor if it is still under user by a stream. |
| */ |
| private AtomicInteger useCount; |
| |
| /** |
| * Constructs an (invalid) FileDescriptor |
| * object. |
| */ |
| public /**/ FileDescriptor() { |
| fd = -1; |
| useCount = new AtomicInteger(); |
| } |
| |
| private /* */ FileDescriptor(int fd) { |
| this.fd = fd; |
| useCount = new AtomicInteger(); |
| } |
| |
| /** |
| * A handle to the standard input stream. Usually, this file |
| * descriptor is not used directly, but rather via the input stream |
| * known as <code>System.in</code>. |
| * |
| * @see java.lang.System#in |
| */ |
| public static final FileDescriptor in = new FileDescriptor(0); |
| |
| /** |
| * A handle to the standard output stream. Usually, this file |
| * descriptor is not used directly, but rather via the output stream |
| * known as <code>System.out</code>. |
| * @see java.lang.System#out |
| */ |
| public static final FileDescriptor out = new FileDescriptor(1); |
| |
| /** |
| * A handle to the standard error stream. Usually, this file |
| * descriptor is not used directly, but rather via the output stream |
| * known as <code>System.err</code>. |
| * |
| * @see java.lang.System#err |
| */ |
| public static final FileDescriptor err = new FileDescriptor(2); |
| |
| /** |
| * Tests if this file descriptor object is valid. |
| * |
| * @return <code>true</code> if the file descriptor object represents a |
| * valid, open file, socket, or other active I/O connection; |
| * <code>false</code> otherwise. |
| */ |
| public boolean valid() { |
| return fd != -1; |
| } |
| |
| /** |
| * Force all system buffers to synchronize with the underlying |
| * device. This method returns after all modified data and |
| * attributes of this FileDescriptor have been written to the |
| * relevant device(s). In particular, if this FileDescriptor |
| * refers to a physical storage medium, such as a file in a file |
| * system, sync will not return until all in-memory modified copies |
| * of buffers associated with this FileDescriptor have been |
| * written to the physical medium. |
| * |
| * sync is meant to be used by code that requires physical |
| * storage (such as a file) to be in a known state For |
| * example, a class that provided a simple transaction facility |
| * might use sync to ensure that all changes to a file caused |
| * by a given transaction were recorded on a storage medium. |
| * |
| * sync only affects buffers downstream of this FileDescriptor. If |
| * any in-memory buffering is being done by the application (for |
| * example, by a BufferedOutputStream object), those buffers must |
| * be flushed into the FileDescriptor (for example, by invoking |
| * OutputStream.flush) before that data will be affected by sync. |
| * |
| * @exception SyncFailedException |
| * Thrown when the buffers cannot be flushed, |
| * or because the system cannot guarantee that all the |
| * buffers have been synchronized with physical media. |
| * @since JDK1.1 |
| */ |
| public native void sync() throws SyncFailedException; |
| |
| /* This routine initializes JNI field offsets for the class */ |
| private static native void initIDs(); |
| |
| static { |
| initIDs(); |
| } |
| |
| // Set up JavaIOFileDescriptorAccess in SharedSecrets |
| static { |
| sun.misc.SharedSecrets.setJavaIOFileDescriptorAccess( |
| new sun.misc.JavaIOFileDescriptorAccess() { |
| public void set(FileDescriptor obj, int fd) { |
| obj.fd = fd; |
| } |
| |
| public int get(FileDescriptor obj) { |
| return obj.fd; |
| } |
| |
| public void setHandle(FileDescriptor obj, long handle) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public long getHandle(FileDescriptor obj) { |
| throw new UnsupportedOperationException(); |
| } |
| } |
| ); |
| } |
| |
| // package private methods used by FIS, FOS and RAF |
| |
| int incrementAndGetUseCount() { |
| return useCount.incrementAndGet(); |
| } |
| |
| int decrementAndGetUseCount() { |
| return useCount.decrementAndGet(); |
| } |
| } |