001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one or more
003 *  contributor license agreements.  See the NOTICE file distributed with
004 *  this work for additional information regarding copyright ownership.
005 *  The ASF licenses this file to You under the Apache License, Version 2.0
006 *  (the "License"); you may not use this file except in compliance with
007 *  the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 */
017package org.apache.commons.compress.utils;
018
019import java.io.FilterInputStream;
020import java.io.IOException;
021import java.io.InputStream;
022
023/**
024 * A stream that limits reading from a wrapped stream to a given number of bytes.
025 * @NotThreadSafe
026 * @since 1.6
027 */
028public class BoundedInputStream extends FilterInputStream {
029    private long bytesRemaining;
030
031    /**
032     * Creates the stream that will at most read the given amount of
033     * bytes from the given stream.
034     * @param in the stream to read from
035     * @param size the maximum amount of bytes to read
036     */
037    public BoundedInputStream(final InputStream in, final long size) {
038        super(in);
039        bytesRemaining = size;
040    }
041
042    @Override
043    public void close() {
044        // there isn't anything to close in this stream and the nested
045        // stream is controlled externally
046    }
047
048    /**
049     * @return bytes remaining to read
050     * @since 1.21
051     */
052    public long getBytesRemaining() {
053        return bytesRemaining;
054    }
055
056    @Override
057    public int read() throws IOException {
058        if (bytesRemaining > 0) {
059            --bytesRemaining;
060            return in.read();
061        }
062        return -1;
063    }
064
065    @Override
066    public int read(final byte[] b, final int off, final int len) throws IOException {
067        if (len == 0) {
068            return 0;
069        }
070        if (bytesRemaining == 0) {
071            return -1;
072        }
073        int bytesToRead = len;
074        if (bytesToRead > bytesRemaining) {
075            bytesToRead = (int) bytesRemaining;
076        }
077        final int bytesRead = in.read(b, off, bytesToRead);
078        if (bytesRead >= 0) {
079            bytesRemaining -= bytesRead;
080        }
081        return bytesRead;
082    }
083
084    /**
085     * @since 1.20
086     */
087    @Override
088    public long skip(final long n) throws IOException {
089        final long bytesToSkip = Math.min(bytesRemaining, n);
090        final long bytesSkipped = in.skip(bytesToSkip);
091        bytesRemaining -= bytesSkipped;
092
093        return bytesSkipped;
094    }
095}