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;
022import java.util.zip.Checksum;
023
024/**
025 * A stream that verifies the checksum of the data read once the stream is
026 * exhausted.
027 * @NotThreadSafe
028 * @since 1.7
029 */
030public class ChecksumVerifyingInputStream extends InputStream {
031
032    private final InputStream in;
033    private long bytesRemaining;
034    private final long expectedChecksum;
035    private final Checksum checksum;
036
037    /**
038     * Constructs a new instance.
039     *
040     * @param checksum Checksum implementation.
041     * @param in the stream to wrap
042     * @param size the of the stream's content
043     * @param expectedChecksum the expected checksum
044     */
045    public ChecksumVerifyingInputStream(final Checksum checksum, final InputStream in,
046                                        final long size, final long expectedChecksum) {
047        this.checksum = checksum;
048        this.in = in;
049        this.expectedChecksum = expectedChecksum;
050        this.bytesRemaining = size;
051    }
052
053    @Override
054    public void close() throws IOException {
055        in.close();
056    }
057
058    /**
059     * @return bytes remaining to read
060     * @since 1.21
061     */
062    public long getBytesRemaining() {
063        return bytesRemaining;
064    }
065
066    /**
067     * Reads a single byte from the stream
068     * @throws IOException if the underlying stream throws or the
069     * stream is exhausted and the Checksum doesn't match the expected
070     * value
071     */
072    @Override
073    public int read() throws IOException {
074        if (bytesRemaining <= 0) {
075            return -1;
076        }
077        final int ret = in.read();
078        if (ret >= 0) {
079            checksum.update(ret);
080            --bytesRemaining;
081        }
082        verify();
083        return ret;
084    }
085
086    /**
087     * Reads a byte array from the stream
088     * @throws IOException if the underlying stream throws or the
089     * stream is exhausted and the Checksum doesn't match the expected
090     * value
091     */
092    @Override
093    public int read(final byte[] b) throws IOException {
094        return read(b, 0, b.length);
095    }
096
097    /**
098     * Reads from the stream into a byte array.
099     * @throws IOException if the underlying stream throws or the
100     * stream is exhausted and the Checksum doesn't match the expected
101     * value
102     */
103    @Override
104    public int read(final byte[] b, final int off, final int len) throws IOException {
105        if (len == 0) {
106            return 0;
107        }
108        final int ret = in.read(b, off, len);
109        if (ret >= 0) {
110            checksum.update(b, off, ret);
111            bytesRemaining -= ret;
112        }
113        verify();
114        return ret;
115    }
116
117    @Override
118    public long skip(final long n) throws IOException {
119        // Can't really skip, we have to hash everything to verify the checksum
120        return read() >= 0 ? 1 : 0;
121    }
122
123    private void verify() throws IOException {
124        if (bytesRemaining <= 0 && expectedChecksum != checksum.getValue()) {
125            throw new IOException("Checksum verification failed");
126        }
127    }
128}