package java.io;
/*
* %W% %E%
*
* Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
/**
* A <code>FilterInputStream</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>FilterInputStream</code> itself simply overrides all methods of
* <code>InputStream</code> with versions that pass all requests to the
* contained input stream. Subclasses of <code>FilterInputStream</code> may
* further override some of these methods and may also provide additional
* methods and fields.
*
* @author Jonathan Payne
* @version %I%, %G%
* @since JDK1.0
*/
public class FilterInputStream extends InputStream {
/**
* The input stream to be filtered.
*/
protected volatile InputStream in;
/**
* Creates a <code>FilterInputStream</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 FilterInputStream(InputStream in) {
this.in = 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 java.io.FilterInputStream#in
*/
public int read() throws IOException {
return in.read();
}
/**
* Reads up to <code>byte.length</code> bytes of data from this input stream
* into an array of bytes. This method blocks until some input is available.
* <p>
* This method simply performs the call <code>read(b, 0, b.length)</code>
* and returns the result. It is important that it does <i>not</i> do
* <code>in.read(b)</code> instead; certain subclasses of
* <code>FilterInputStream</code> depend on the implementation strategy
* actually used.
*
* @param b
* the buffer into which the data is read.
* @return the total number of bytes read into the buffer, or
* <code>-1</code> if there is no more data because the end of the
* stream has been reached.
* @exception IOException
* if an I/O error occurs.
* @see java.io.FilterInputStream#read(byte[], int, int)
*/
public int read(byte b[]) throws IOException {
return read(b, 0, b.length);
}
/**
* Reads up to <code>len</code> bytes of data from this input stream into an
* array of bytes. If <code>len</code> is not zero, the method blocks until
* some input is available; otherwise, no bytes are read and <code>0</code>
* is returned.
* <p>
* This method simply performs <code>in.read(b, off, len)</code> and returns
* the result.
*
* @param b
* the buffer into which the data is read.
* @param off
* the start offset in the destination array <code>b</code>
* @param len
* the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* <code>-1</code> if there is no more data because the end of the
* stream has been reached.
* @exception NullPointerException
* If <code>b</code> is <code>null</code>.
* @exception IndexOutOfBoundsException
* If <code>off</code> is negative, <code>len</code> is
* negative, or <code>len</code> is greater than
* <code>b.length - off</code>
* @exception IOException
* if an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
public int read(byte b[], int off, int len) throws IOException {
return in.read(b, off, len);
}
/**
* {@inheritDoc}
* <p>
* This method simply performs <code>in.skip(n)</code>.
*/
public long skip(long n) throws IOException {
return in.skip(n);
}
/**
* Returns an estimate of the number of bytes that can be read (or skipped
* over) from this input stream without blocking by the next caller of a
* method for this input stream. The next caller might be the same thread or
* another thread. A single read or skip of this many bytes will not block,
* but may read or skip fewer bytes.
* <p>
* This method returns the result of {@link #in in}.available().
*
* @return an estimate of the number of bytes that can be read (or skipped
* over) from this input stream without blocking.
* @exception IOException
* if an I/O error occurs.
*/
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 java.io.FilterInputStream#in
*/
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 java.io.FilterInputStream#in
* @see java.io.FilterInputStream#reset()
*/
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 java.io.FilterInputStream#in
* @see java.io.FilterInputStream#mark(int)
*/
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 java.io.FilterInputStream#in
* @see java.io.InputStream#mark(int)
* @see java.io.InputStream#reset()
*/
public boolean markSupported() {
return in.markSupported();
}
}