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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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*/
package java.io;
/**
* A {@code FilterInputStream} wraps 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}
* itself simply overrides select methods of {@code InputStream} with versions
* that pass all requests to the wrapped input stream. Subclasses of
* {@code FilterInputStream} may of course override any methods declared or
* inherited by {@code FilterInputStream}, and may also provide additional
* fields and methods.
*
* @author Jonathan Payne
* @since 1.0
*/
public class FilterInputStream extends InputStream {
/**
* The input stream to be filtered.
*/
protected volatile InputStream in;
/**
* Creates a {@code FilterInputStream}
* by assigning the argument {@code in}
* to the field {@code this.in} so as
* to remember it for later use.
*
* @param in the underlying input stream, or {@code null} if
* this instance is to be created without an underlying stream.
*/
protected FilterInputStream(InputStream in) {
this.in = in;
}
/**
* {@inheritDoc}
* @implSpec
* This method simply performs {@code in.read()} and returns the result.
*
* @return {@inheritDoc}
* @throws IOException {@inheritDoc}
* @see java.io.FilterInputStream#in
*/
@Override
public int read() throws IOException {
return in.read();
}
/**
* Reads up to {@code b.length} bytes of data from this
* input stream into an array of bytes. This method blocks until some
* input is available.
*
* @implSpec
* This method simply performs the call
* {@code read(b, 0, b.length)} and returns
* the result. It is important that it does
* not do {@code in.read(b)} instead;
* certain subclasses of {@code FilterInputStream}
* depend on the implementation strategy actually
* used.
*
* @param b {@inheritDoc}
* @return {@inheritDoc}
* @throws IOException if an I/O error occurs.
* @see java.io.FilterInputStream#read(byte[], int, int)
*/
@Override
public int read(byte[] b) throws IOException {
return read(b, 0, b.length);
}
/**
* Reads up to {@code len} bytes of data from this input stream
* into an array of bytes. If {@code len} is not zero, the method
* blocks until some input is available; otherwise, no
* bytes are read and {@code 0} is returned.
*
* @implSpec
* This method simply performs {@code in.read(b, off, len)}
* and returns the result.
*
* @param b {@inheritDoc}
* @param off {@inheritDoc}
* @param len {@inheritDoc}
* @return {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @throws IndexOutOfBoundsException {@inheritDoc}
* @throws IOException if an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
@Override
public int read(byte[] b, int off, int len) throws IOException {
return in.read(b, off, len);
}
/**
* Skips over and discards {@code n} bytes of data from the
* input stream. The {@code skip} method may, for a variety of
* reasons, end up skipping over some smaller number of bytes,
* possibly {@code 0}. The actual number of bytes skipped is
* returned.
*
* @implSpec
* This method simply performs {@code in.skip(n)} and returns the result.
*
* @param n {@inheritDoc}
* @return the actual number of bytes skipped.
* @throws IOException if {@code in.skip(n)} throws an IOException.
*/
@Override
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.
*
* @implSpec
* This method returns the result of {@code in.available()}.
*
* @return an estimate of the number of bytes that can be read (or
* skipped over) from this input stream without blocking.
* @throws IOException {@inheritDoc}
*/
@Override
public int available() throws IOException {
return in.available();
}
/**
* {@inheritDoc}
* @implSpec
* This method simply performs {@code in.close()}.
*
* @throws IOException {@inheritDoc}
* @see java.io.FilterInputStream#in
*/
@Override
public void close() throws IOException {
in.close();
}
/**
* Marks the current position in this input stream. A subsequent
* call to the {@code reset} method repositions this stream at
* the last marked position so that subsequent reads re-read the same bytes.
*
* The {@code readlimit} argument tells this input stream to
* allow that many bytes to be read before the mark position gets
* invalidated.
*
* @implSpec
* This method simply performs {@code in.mark(readlimit)}.
*
* @param readlimit {@inheritDoc}
* @see java.io.FilterInputStream#in
* @see java.io.FilterInputStream#reset()
*/
@Override
public void mark(int readlimit) {
in.mark(readlimit);
}
/**
* Repositions this stream to the position at the time the
* {@code mark} method was last called on this input stream.
*
* 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.
*
* @implSpec
* This method simply performs {@code in.reset()}.
*
* @throws IOException {@inheritDoc}
* @see java.io.FilterInputStream#in
* @see java.io.FilterInputStream#mark(int)
*/
@Override
public void reset() throws IOException {
in.reset();
}
/**
* Tests if this input stream supports the {@code mark}
* and {@code reset} methods.
*
* @implSpec
* This method simply performs {@code in.markSupported()}.
*
* @return {@code true} if this stream type supports the
* {@code mark} and {@code reset} method;
* {@code false} otherwise.
* @see java.io.FilterInputStream#in
* @see java.io.InputStream#mark(int)
* @see java.io.InputStream#reset()
*/
@Override
public boolean markSupported() {
return in.markSupported();
}
}