/*
* Copyright (c) 1995, 2015, 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.ArrayList;
import java.util.List;
import jdk.internal.misc.JavaIOFileDescriptorAccess;
import jdk.internal.misc.SharedSecrets;
/**
* 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 1.0
*/
public final class FileDescriptor {
private int fd;
private Closeable parent;
private List<Closeable> otherParents;
private boolean closed;
/**
* true, if file is opened for appending.
*/
private boolean append;
/**
* Constructs an (invalid) FileDescriptor
* object.
*/
public FileDescriptor() {
fd = -1;
}
private FileDescriptor(int fd) {
this.fd = fd;
this.append = getAppend(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 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 1.1
*/
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 {
SharedSecrets.setJavaIOFileDescriptorAccess(
new JavaIOFileDescriptorAccess() {
public void set(FileDescriptor obj, int fd) {
obj.fd = fd;
}
public int get(FileDescriptor obj) {
return obj.fd;
}
public void setAppend(FileDescriptor obj, boolean append) {
obj.append = append;
}
public boolean getAppend(FileDescriptor obj) {
return obj.append;
}
public void setHandle(FileDescriptor obj, long handle) {
throw new UnsupportedOperationException();
}
public long getHandle(FileDescriptor obj) {
throw new UnsupportedOperationException();
}
}
);
}
/**
* Returns true, if the file was opened for appending.
*/
private static native boolean getAppend(int fd);
/*
* Package private methods to track referents.
* If multiple streams point to the same FileDescriptor, we cycle
* through the list of all referents and call close()
*/
/**
* Attach a Closeable to this FD for tracking.
* parent reference is added to otherParents when
* needed to make closeAll simpler.
*/
synchronized void attach(Closeable c) {
if (parent == null) {
// first caller gets to do this
parent = c;
} else if (otherParents == null) {
otherParents = new ArrayList<>();
otherParents.add(parent);
otherParents.add(c);
} else {
otherParents.add(c);
}
}
/**
* Cycle through all Closeables sharing this FD and call
* close() on each one.
*
* The caller closeable gets to call close0().
*/
@SuppressWarnings("try")
synchronized void closeAll(Closeable releaser) throws IOException {
if (!closed) {
closed = true;
IOException ioe = null;
try (releaser) {
if (otherParents != null) {
for (Closeable referent : otherParents) {
try {
referent.close();
} catch(IOException x) {
if (ioe == null) {
ioe = x;
} else {
ioe.addSuppressed(x);
}
}
}
}
} catch(IOException ex) {
/*
* If releaser close() throws IOException
* add other exceptions as suppressed.
*/
if (ioe != null)
ex.addSuppressed(ioe);
ioe = ex;
} finally {
if (ioe != null)
throw ioe;
}
}
}
}