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package java.io;
A 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 FilterInputStream itself simply overrides select methods of InputStream with versions that pass all requests to the wrapped input stream. Subclasses of FilterInputStream may of course override any methods declared or inherited by FilterInputStream, and may also provide additional fields and methods. Author: Jonathan Payne Since: 1.0
/**
* 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.
/**
* 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. Params: - in – the underlying input stream, or
null if this instance is to be created without an underlying stream.
/**
* 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;
}
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. Throws: - IOException – if an I/O error occurs.
See Also: Implementation Requirements: This method simply performs in.read() and returns the result. Returns: the next byte of data, or -1 if the end of the stream is reached.
/**
* Reads the next byte of data from this input stream. The value
* byte is returned as an {@code int} in the range
* {@code 0} to {@code 255}. If no byte is available
* because the end of the stream has been reached, the value
* {@code -1} is returned. This method blocks until input data
* is available, the end of the stream is detected, or an exception
* is thrown.
*
* @implSpec
* This method simply performs {@code in.read()} and returns the result.
*
* @return the next byte of data, or {@code -1} if the end of the
* stream is reached.
* @throws IOException if an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
@Override
public int read() throws IOException {
return in.read();
}
Reads up to b.length bytes of data from this input stream into an array of bytes. This method blocks until some input is available. Params: - b – the buffer into which the data is read.
Throws: - IOException – if an I/O error occurs.
See Also: Implementation Requirements: 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. Returns: 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.
/**
* 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
* <i>not</i> do {@code in.read(b)} instead;
* certain subclasses of {@code 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
* {@code -1} if there is no more data because the end of
* the stream has been reached.
* @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 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. Params: - b – the buffer into which the data is read.
- off – the start offset in the destination array
b - len – the maximum number of bytes read.
Throws: - NullPointerException – If
b is null. - IndexOutOfBoundsException – If
off is negative, len is negative, or len is greater than b.length - off - IOException – if an I/O error occurs.
See Also: Implementation Requirements: This method simply performs in.read(b, off, len) and returns the result. Returns: 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.
/**
* 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 the buffer into which the data is read.
* @param off the start offset in the destination array {@code b}
* @param len the maximum number of bytes read.
* @return the total number of bytes read into the buffer, or
* {@code -1} if there is no more data because the end of
* the stream has been reached.
* @throws NullPointerException If {@code b} is {@code null}.
* @throws IndexOutOfBoundsException If {@code off} is negative,
* {@code len} is negative, or {@code len} is greater than
* {@code b.length - off}
* @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 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. Params: - n – the number of bytes to be skipped.
Throws: - IOException – if
in.skip(n) throws an IOException.
Implementation Requirements: This method simply performs in.skip(n) and returns the result. Returns: the actual number of bytes skipped.
/**
* 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 the number of bytes to be skipped.
* @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.
Throws: - IOException – if an I/O error occurs.
Implementation Requirements: This method returns the result of in.available(). Returns: an estimate of the number of bytes that can be read (or
skipped over) from this input stream without blocking.
/**
* 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 if an I/O error occurs.
*/
@Override
public int available() throws IOException {
return in.available();
}
Closes this input stream and releases any system resources
associated with the stream.
Throws: - IOException – if an I/O error occurs.
See Also: Implementation Requirements: This method simply performs in.close().
/**
* Closes this input stream and releases any system resources
* associated with the stream.
*
* @implSpec
* This method simply performs {@code in.close()}.
*
* @throws IOException if an I/O error occurs.
* @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 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.
Params: - readlimit – the maximum limit of bytes that can be read before
the mark position becomes invalid.
See Also: Implementation Requirements: This method simply performs in.mark(readlimit).
/**
* 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.
* <p>
* 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 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()
*/
@Override
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.
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.
Throws: - IOException – if the stream has not been marked or if the
mark has been invalidated.
See Also: Implementation Requirements: This method simply performs in.reset().
/**
* Repositions this stream to the position at the time the
* {@code mark} method was last called on this input stream.
* <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.
*
* @implSpec
* This method simply performs {@code in.reset()}.
*
* @throws 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)
*/
@Override
public synchronized void reset() throws IOException {
in.reset();
}
Tests if this input stream supports the mark and reset methods. See Also: Implementation Requirements: This method simply performs in.markSupported(). Returns: true if this stream type supports the mark and reset method; false otherwise.
/**
* 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();
}
}