/*
* @(#)FileDescriptor.java 1.26 06/10/10
*
* Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program 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.
*
* This program 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 at /legal/license.txt).
*
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
* information or have any questions.
*
*/
package java.io;
/**
* 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.
*
* @version 1.18, 02/02/00
* @see java.io.FileInputStream
* @see java.io.FileOutputStream
* @since JDK1.0
*/
public final class FileDescriptor {
private int fd;
/**
* Constructs an (invalid) FileDescriptor
* object.
*/
public /**/ FileDescriptor() {
fd = -1;
}
private /* */ FileDescriptor(int fd) {
this.fd = fd;
}
/**
* 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 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();
static {
initIDs();
}
}