/src/windows/classes/java/io/FileDescriptor.java
Java | 180 lines | 53 code | 24 blank | 103 comment | 3 complexity | d5e39ff7f883b954354ac2b69f23d919 MD5 | raw file
- /*
- * Copyright (c) 2003, 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
- * {@link FileInputStream} or {@link FileOutputStream} to contain it.
- *
- * <p>Applications should not create their own file descriptors.
- *
- * @author Pavani Diwanji
- * @since JDK1.0
- */
- public final class FileDescriptor {
- private int fd;
- private long handle;
- /**
- * A use 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 use by any stream.
- */
- private AtomicInteger useCount;
- /**
- * Constructs an (invalid) FileDescriptor
- * object.
- */
- public /**/ FileDescriptor() {
- fd = -1;
- handle = -1;
- useCount = new AtomicInteger();
- }
- 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) {
- obj.handle = handle;
- }
- public long getHandle(FileDescriptor obj) {
- return obj.handle;
- }
- }
- );
- }
- /**
- * 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}.
- *
- * @see java.lang.System#in
- */
- public static final FileDescriptor in = standardStream(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}.
- * @see java.lang.System#out
- */
- public static final FileDescriptor out = standardStream(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}.
- *
- * @see java.lang.System#err
- */
- public static final FileDescriptor err = standardStream(2);
- /**
- * Tests if this file descriptor object is valid.
- *
- * @return {@code true} if the file descriptor object represents a
- * valid, open file, socket, or other active I/O connection;
- * {@code false} otherwise.
- */
- public boolean valid() {
- return ((handle != -1) || (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 FileDesecriptor 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();
- private static native long set(int d);
- private static FileDescriptor standardStream(int fd) {
- FileDescriptor desc = new FileDescriptor();
- desc.handle = set(fd);
- return desc;
- }
- // package private methods used by FIS, FOS and RAF.
- int incrementAndGetUseCount() {
- return useCount.incrementAndGet();
- }
- int decrementAndGetUseCount() {
- return useCount.decrementAndGet();
- }
- }