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/*
* Copyright (c) 2007, 2008, 2011, 2012, 2015 Eike Stepper (Berlin, Germany) and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Eike Stepper - initial API and implementation
*/
package org.eclipse.net4j.util.io;
import java.io.IOException;
import java.io.InputStream;
/**
* A <code>DelegatingInputStream</code> contains some other input stream, which it uses as its basic source of data,
* possibly transforming the data along the way or providing additional functionality. The class
* <code>DelegatingInputStream</code> itself simply overrides all (see note below) methods of <code>InputStream</code>
* with versions that pass all requests to the contained input stream. Subclasses of <code>DelegatingInputStream</code>
* may further override some of these methods and may also provide additional methods and fields.
* <p>
* <b>Note:</b> The only difference to {@link java.io.FilterInputStream} is that <code>DelegatingInputStream</code> does
* <b>not</b> override {@link #read(byte[])} or {@link #read(byte[], int, int)} but rather exposes the original
* implementations of <code>InputStream</code> which call {@link #read()} instead of their delegate counterparts.
*
* @author Eike Stepper
*/
public class DelegatingInputStream extends InputStream
{
/**
* The input stream to be filtered.
*/
protected volatile InputStream in;
/**
* Creates a <code>DelegatingInputStream</code> by assigning the argument <code>in</code> to the field
* <code>this.in</code> so as to remember it for later use.
*
* @param in
* the underlying input stream, or <code>null</code> if this instance is to be created without an underlying
* stream.
*/
protected DelegatingInputStream(InputStream in)
{
this.in = in;
}
public InputStream getDelegate()
{
return in;
}
/**
* Reads the next byte of data from this input stream. The value byte is returned as an <code>int</code> in the range
* <code>0</code> to <code>255</code>. If no byte is available because the end of the stream has been reached, the
* value <code>-1</code> is returned. This method blocks until input data is available, the end of the stream is
* detected, or an exception is thrown.
* <p>
* This method simply performs <code>in.read()</code> and returns the result.
*
* @return the next byte of data, or <code>-1</code> if the end of the stream is reached.
* @exception IOException
* if an I/O error occurs.
* @see DelegatingInputStream#in
*/
@Override
public int read() throws IOException
{
return in.read();
}
/**
* Skips over and discards <code>n</code> bytes of data from the input stream. The <code>skip</code> method may, for a
* variety of reasons, end up skipping over some smaller number of bytes, possibly <code>0</code>. The actual number
* of bytes skipped is returned.
* <p>
* This method simply performs <code>in.skip(n)</code>.
*
* @param n
* the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @exception IOException
* if an I/O error occurs.
*/
@Override
public long skip(long n) throws IOException
{
return in.skip(n);
}
/**
* Returns the number of bytes that can be read from this input stream without blocking.
* <p>
* This method simply performs <code>in.available()</code> and returns the result.
*
* @return the number of bytes that can be read from the input stream without blocking.
* @exception IOException
* if an I/O error occurs.
* @see DelegatingInputStream#in
*/
@Override
public int available() throws IOException
{
return in.available();
}
/**
* Closes this input stream and releases any system resources associated with the stream. This method simply performs
* <code>in.close()</code>.
*
* @exception IOException
* if an I/O error occurs.
* @see DelegatingInputStream#in
*/
@Override
public void close() throws IOException
{
in.close();
}
/**
* Marks the current position in this input stream. A subsequent call to the <code>reset</code> method repositions
* this stream at the last marked position so that subsequent reads re-read the same bytes.
* <p>
* The <code>readlimit</code> argument tells this input stream to allow that many bytes to be read before the mark
* position gets invalidated.
* <p>
* This method simply performs <code>in.mark(readlimit)</code>.
*
* @param readlimit
* the maximum limit of bytes that can be read before the mark position becomes invalid.
* @see DelegatingInputStream#in
* @see DelegatingInputStream#reset()
*/
@Override
public synchronized void mark(int readlimit)
{
in.mark(readlimit);
}
/**
* Repositions this stream to the position at the time the <code>mark</code> method was last called on this input
* stream.
* <p>
* This method simply performs <code>in.reset()</code>.
* <p>
* Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the
* stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the
* parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it
* fails. If this happens within readlimit bytes, it allows the outer code to reset the stream and try another parser.
*
* @exception IOException
* if the stream has not been marked or if the mark has been invalidated.
* @see DelegatingInputStream#in
* @see DelegatingInputStream#mark(int)
*/
@Override
public synchronized void reset() throws IOException
{
in.reset();
}
/**
* Tests if this input stream supports the <code>mark</code> and <code>reset</code> methods. This method simply
* performs <code>in.markSupported()</code>.
*
* @return <code>true</code> if this stream type supports the <code>mark</code> and <code>reset</code> method;
* <code>false</code> otherwise.
* @see DelegatingInputStream#in
* @see java.io.InputStream#mark(int)
* @see java.io.InputStream#reset()
*/
@Override
public boolean markSupported()
{
return in.markSupported();
}
}
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