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/*
 *  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.
     *
     * 

Warning: 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. *

* 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(); } @Override public int read(byte[] buffer, int byteOffset, int byteCount) throws IOException { return in.read(buffer, byteOffset, byteCount); } /** * 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); } }





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