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 *
017 */
018package org.apache.commons.compress.utils;
019
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 InputStream {
029    private final InputStream in;
030    private long bytesRemaining;
031
032    /**
033     * Creates the stream that will at most read the given amount of
034     * bytes from the given stream.
035     * @param in the stream to read from
036     * @param size the maximum amount of bytes to read
037     */
038    public BoundedInputStream(final InputStream in, final long size) {
039        this.in = in;
040        bytesRemaining = size;
041    }
042
043    @Override
044    public int read() throws IOException {
045        if (bytesRemaining > 0) {
046            --bytesRemaining;
047            return in.read();
048        }
049        return -1;
050    }
051
052    @Override
053    public int read(final byte[] b, final int off, final int len) throws IOException {
054        if (bytesRemaining == 0) {
055            return -1;
056        }
057        int bytesToRead = len;
058        if (bytesToRead > bytesRemaining) {
059            bytesToRead = (int) bytesRemaining;
060        }
061        final int bytesRead = in.read(b, off, bytesToRead);
062        if (bytesRead >= 0) {
063            bytesRemaining -= bytesRead;
064        }
065        return bytesRead;
066    }
067
068    @Override
069    public void close() {
070        // there isn't anything to close in this stream and the nested
071        // stream is controlled externally
072    }
073}