/*
* Copyright (c) 1994, 2019, 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
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*/
package java.io;
/**
* This class is the superclass of all classes that filter output
* streams. These streams sit on top of an already existing output
* stream (the <i>underlying</i> output stream) which it uses as its
* basic sink of data, but possibly transforming the data along the
* way or providing additional functionality.
* <p>
* The class {@code FilterOutputStream} itself simply overrides
* all methods of {@code OutputStream} with versions that pass
* all requests to the underlying output stream. Subclasses of
* {@code FilterOutputStream} may further override some of these
* methods as well as provide additional methods and fields.
*
* @author Jonathan Payne
* @since 1.0
*/
public class FilterOutputStream extends OutputStream {
/**
* The underlying output stream to be filtered.
*/
protected OutputStream out;
/**
* Whether the stream is closed; implicitly initialized to false.
*/
private volatile boolean closed;
/**
* Object used to prevent a race on the 'closed' instance variable.
*/
private final Object closeLock = new Object();
/**
* Creates an output stream filter built on top of the specified
* underlying output stream.
*
* @param out the underlying output stream to be assigned to
* the field {@code this.out} for later use, or
* {@code null} if this instance is to be
* created without an underlying stream.
*/
public FilterOutputStream(OutputStream out) {
this.out = out;
}
/**
* Writes the specified {@code byte} to this output stream.
* <p>
* The {@code write} method of {@code FilterOutputStream}
* calls the {@code write} method of its underlying output stream,
* that is, it performs {@code out.write(b)}.
* <p>
* Implements the abstract {@code write} method of {@code OutputStream}.
*
* @param b the {@code byte}.
* @throws IOException if an I/O error occurs.
*/
@Override
public void write(int b) throws IOException {
out.write(b);
}
/**
* Writes {@code b.length} bytes to this output stream.
* <p>
* The {@code write} method of {@code FilterOutputStream}
* calls its {@code write} method of three arguments with the
* arguments {@code b}, {@code 0}, and
* {@code b.length}.
* <p>
* Note that this method does not call the one-argument
* {@code write} method of its underlying output stream with
* the single argument {@code b}.
*
* @param b the data to be written.
* @throws IOException if an I/O error occurs.
* @see java.io.FilterOutputStream#write(byte[], int, int)
*/
@Override
public void write(byte b[]) throws IOException {
write(b, 0, b.length);
}
/**
* Writes {@code len} bytes from the specified
* {@code byte} array starting at offset {@code off} to
* this output stream.
* <p>
* The {@code write} method of {@code FilterOutputStream}
* calls the {@code write} method of one argument on each
* {@code byte} to output.
* <p>
* Note that this method does not call the {@code write} method
* of its underlying output stream with the same arguments. Subclasses
* of {@code FilterOutputStream} should provide a more efficient
* implementation of this method.
*
* @param b the data.
* @param off the start offset in the data.
* @param len the number of bytes to write.
* @throws IOException if an I/O error occurs.
* @see java.io.FilterOutputStream#write(int)
*/
@Override
public void write(byte b[], int off, int len) throws IOException {
if ((off | len | (b.length - (len + off)) | (off + len)) < 0)
throw new IndexOutOfBoundsException();
for (int i = 0 ; i < len ; i++) {
write(b[off + i]);
}
}
/**
* Flushes this output stream and forces any buffered output bytes
* to be written out to the stream.
* <p>
* The {@code flush} method of {@code FilterOutputStream}
* calls the {@code flush} method of its underlying output stream.
*
* @throws IOException if an I/O error occurs.
* @see java.io.FilterOutputStream#out
*/
@Override
public void flush() throws IOException {
out.flush();
}
/**
* Closes this output stream and releases any system resources
* associated with the stream.
* <p>
* When not already closed, the {@code close} method of {@code
* FilterOutputStream} calls its {@code flush} method, and then
* calls the {@code close} method of its underlying output stream.
*
* @throws IOException if an I/O error occurs.
* @see java.io.FilterOutputStream#flush()
* @see java.io.FilterOutputStream#out
*/
@Override
public void close() throws IOException {
if (closed) {
return;
}
synchronized (closeLock) {
if (closed) {
return;
}
closed = true;
}
Throwable flushException = null;
try {
flush();
} catch (Throwable e) {
flushException = e;
throw e;
} finally {
if (flushException == null) {
out.close();
} else {
try {
out.close();
} catch (Throwable closeException) {
// evaluate possible precedence of flushException over closeException
if ((flushException instanceof ThreadDeath) &&
!(closeException instanceof ThreadDeath)) {
flushException.addSuppressed(closeException);
throw (ThreadDeath) flushException;
}
if (flushException != closeException) {
closeException.addSuppressed(flushException);
}
throw closeException;
}
}
}
}
}