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;
022import java.util.zip.Checksum;
023
024/**
025 * Verifies the checksum of the data read once the stream is
026 * exhausted.
027 *
028 * @NotThreadSafe
029 * @since 1.7
030 */
031public class ChecksumVerifyingInputStream extends FilterInputStream {
032
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        super(in);
048        this.checksum = checksum;
049        this.expectedChecksum = expectedChecksum;
050        this.bytesRemaining = size;
051    }
052
053    /**
054     * @return bytes remaining to read
055     * @since 1.21
056     */
057    public long getBytesRemaining() {
058        return bytesRemaining;
059    }
060
061    /**
062     * Reads a single byte from the stream
063     * @throws IOException if the underlying stream throws or the
064     * stream is exhausted and the Checksum doesn't match the expected
065     * value
066     */
067    @Override
068    public int read() throws IOException {
069        if (bytesRemaining <= 0) {
070            return -1;
071        }
072        final int ret = in.read();
073        if (ret >= 0) {
074            checksum.update(ret);
075            --bytesRemaining;
076        }
077        verify();
078        return ret;
079    }
080
081    /**
082     * Reads from the stream into a byte array.
083     * @throws IOException if the underlying stream throws or the
084     * stream is exhausted and the Checksum doesn't match the expected
085     * value
086     */
087    @Override
088    public int read(final byte[] b, final int off, final int len) throws IOException {
089        if (len == 0) {
090            return 0;
091        }
092        final int ret = in.read(b, off, len);
093        if (ret >= 0) {
094            checksum.update(b, off, ret);
095            bytesRemaining -= ret;
096        }
097        verify();
098        return ret;
099    }
100
101    @Override
102    public long skip(final long n) throws IOException {
103        // Can't really skip, we have to hash everything to verify the checksum
104        return read() >= 0 ? 1 : 0;
105    }
106
107    private void verify() throws IOException {
108        if (bytesRemaining <= 0 && expectedChecksum != checksum.getValue()) {
109            throw new IOException("Checksum verification failed");
110        }
111    }
112}