/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package java.io;
/**
* Wraps an existing {@link InputStream} and performs some transformation on
* the input data while it is being read. Transformations can be anything from a
* simple byte-wise filtering input data to an on-the-fly compression or
* decompression of the underlying stream. Input streams that wrap another input
* stream and provide some additional functionality on top of it usually inherit
* from this class.
*
* @see FilterOutputStream
*/
public class FilterInputStream extends InputStream {
/**
* The source input stream that is filtered.
*/
protected volatile InputStream in;
/**
* Constructs a new {@code FilterInputStream} with the specified input
* stream as source.
*
* <p><strong>Warning:</strong> passing a null source creates an invalid
* {@code FilterInputStream}, that fails on every method that is not
* overridden. Subclasses should check for null in their constructors.
*
* @param in the input stream to filter reads on.
*/
protected FilterInputStream(InputStream in) {
this.in = in;
}
@Override
public int available() throws IOException {
return in.available();
}
/**
* Closes this stream. This implementation closes the filtered stream.
*
* @throws IOException
* if an error occurs while closing this stream.
*/
@Override
public void close() throws IOException {
in.close();
}
/**
* Sets a mark position in this stream. The parameter {@code readlimit}
* indicates how many bytes can be read before the mark is invalidated.
* Sending {@code reset()} will reposition this stream back to the marked
* position, provided that {@code readlimit} has not been surpassed.
* <p>
* This implementation sets a mark in the filtered stream.
*
* @param readlimit
* the number of bytes that can be read from this stream before
* the mark is invalidated.
* @see #markSupported()
* @see #reset()
*/
@Override
public synchronized void mark(int readlimit) {
in.mark(readlimit);
}
/**
* Indicates whether this stream supports {@code mark()} and {@code reset()}.
* This implementation returns whether or not the filtered stream supports
* marking.
*
* @return {@code true} if {@code mark()} and {@code reset()} are supported,
* {@code false} otherwise.
* @see #mark(int)
* @see #reset()
* @see #skip(long)
*/
@Override
public boolean markSupported() {
return in.markSupported();
}
/**
* Reads a single byte from the filtered stream and returns it as an integer
* in the range from 0 to 255. Returns -1 if the end of this stream has been
* reached.
*
* @return the byte read or -1 if the end of the filtered stream has been
* reached.
* @throws IOException
* if the stream is closed or another IOException occurs.
*/
@Override
public int read() throws IOException {
return in.read();
}
/**
* Reads at most {@code count} bytes from this stream and stores them in the
* byte array {@code buffer} starting at {@code offset}. Returns the number
* of bytes actually read or -1 if no bytes have been read and the end of
* this stream has been reached. This implementation reads bytes from the
* filtered stream.
*
* @param buffer
* the byte array in which to store the bytes read.
* @param offset
* the initial position in {@code buffer} to store the bytes
* read from this stream.
* @param count
* the maximum number of bytes to store in {@code buffer}.
* @return the number of bytes actually read or -1 if the end of the
* filtered stream has been reached while reading.
* @throws IOException
* if this stream is closed or another I/O error occurs.
*/
@Override
public int read(byte[] buffer, int offset, int count) throws IOException {
return in.read(buffer, offset, count);
}
/**
* Resets this stream to the last marked location. This implementation
* resets the target stream.
*
* @throws IOException
* if this stream is already closed, no mark has been set or the
* mark is no longer valid because more than {@code readlimit}
* bytes have been read since setting the mark.
* @see #mark(int)
* @see #markSupported()
*/
@Override
public synchronized void reset() throws IOException {
in.reset();
}
/**
* Skips {@code byteCount} bytes in this stream. Subsequent
* calls to {@code read} will not return these bytes unless {@code reset} is
* used. This implementation skips {@code byteCount} bytes in the
* filtered stream.
*
* @return the number of bytes actually skipped.
* @throws IOException
* if this stream is closed or another IOException occurs.
* @see #mark(int)
* @see #reset()
*/
@Override
public long skip(long byteCount) throws IOException {
return in.skip(byteCount);
}
}