    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}