FilterInputStream 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 FilterInputStream
- * itself simply overrides all methods of
- * InputStream with versions that
- * pass all requests to the contained input
- * stream. Subclasses of FilterInputStream
- * may further override some of these methods
- * and may also provide additional methods
- * and fields.
- *
- * @author Jonathan Payne
- * @since JDK1.0
- */
-public
-class FilterInputStream extends InputStream {
- /**
- * The input stream to be filtered.
- */
- protected volatile InputStream in;
-
- /**
- * Creates a FilterInputStream
- * by assigning the argument in
- * to the field this.in so as
- * to remember it for later use.
- *
- * @param in the underlying input stream, or null 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 int in the range
- * 0 to 255. If no byte is available
- * because the end of the stream has been reached, the value
- * -1 is returned. This method blocks until input data
- * is available, the end of the stream is detected, or an exception
- * is thrown.
- *
- * This method
- * simply performs in.read() and returns the result.
- *
- * @return the next byte of data, or -1 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 byte.length bytes of data from this
- * input stream into an array of bytes. This method blocks until some
- * input is available.
- *
- * This method simply performs the call
- * read(b, 0, b.length) and returns
- * the result. It is important that it does
- * not do in.read(b) instead;
- * certain subclasses of FilterInputStream
- * 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
- * -1 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 len bytes of data from this input stream
- * into an array of bytes. If len is not zero, the method
- * blocks until some input is available; otherwise, no
- * bytes are read and 0 is returned.
- *
- * This method simply performs in.read(b, off, len)
- * and returns the result.
- *
- * @param b the buffer into which the data is read.
- * @param off the start offset in the destination array b
- * @param len the maximum number of bytes read.
- * @return the total number of bytes read into the buffer, or
- * -1 if there is no more data because the end of
- * the stream has been reached.
- * @exception NullPointerException If b is null.
- * @exception IndexOutOfBoundsException If off is negative,
- * len is negative, or len is greater than
- * b.length - off
- * @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);
- }
-
- /**
- * Skips over and discards n bytes of data from the
- * input stream. The skip method may, for a variety of
- * reasons, end up skipping over some smaller number of bytes,
- * possibly 0. The actual number of bytes skipped is
- * returned.
- *
- * This method simply performs in.skip(n).
- *
- * @param n the number of bytes to be skipped.
- * @return the actual number of bytes skipped.
- * @exception IOException if the stream does not support seek,
- * or if some other I/O error occurs.
- */
- 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.
- *
- * 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 in.close().
- *
- * @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 reset method repositions this stream at
- * the last marked position so that subsequent reads re-read the same bytes.
- *
- * The readlimit argument tells this input stream to
- * allow that many bytes to be read before the mark position gets
- * invalidated.
- *
- * This method simply performs in.mark(readlimit).
- *
- * @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
- * mark method was last called on this input stream.
- *
- * This method
- * simply performs in.reset().
- *
- * 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 mark
- * and reset methods.
- * This method
- * simply performs in.markSupported().
- *
- * @return true if this stream type supports the
- * mark and reset method;
- * false otherwise.
- * @see java.io.FilterInputStream#in
- * @see java.io.InputStream#mark(int)
- * @see java.io.InputStream#reset()
- */
- public boolean markSupported() {
- return in.markSupported();
- }
-}