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.Objects;
023import java.util.zip.Checksum;
024
025/**
026 * A stream that calculates the checksum of the data read.
027 * @NotThreadSafe
028 * @since 1.14
029 */
030public class ChecksumCalculatingInputStream extends InputStream {
031    private final InputStream in;
032    private final Checksum checksum;
033
034    public ChecksumCalculatingInputStream(final Checksum checksum, final InputStream inputStream) {
035
036        Objects.requireNonNull(checksum, "checksum");
037        Objects.requireNonNull(inputStream, "in");
038
039        this.checksum = checksum;
040        this.in = inputStream;
041    }
042
043    /**
044     * Reads a single byte from the stream
045     * @throws IOException if the underlying stream throws or the
046     * stream is exhausted and the Checksum doesn't match the expected
047     * value
048     */
049    @Override
050    public int read() throws IOException {
051        final int ret = in.read();
052        if (ret >= 0) {
053            checksum.update(ret);
054        }
055        return ret;
056    }
057
058    /**
059     * Reads a byte array from the stream
060     * @throws IOException if the underlying stream throws or the
061     * stream is exhausted and the Checksum doesn't match the expected
062     * value
063     */
064    @Override
065    public int read(final byte[] b) throws IOException {
066        return read(b, 0, b.length);
067    }
068
069    /**
070     * Reads from the stream into a byte array.
071     * @throws IOException if the underlying stream throws or the
072     * stream is exhausted and the Checksum doesn't match the expected
073     * value
074     */
075    @Override
076    public int read(final byte[] b, final int off, final int len) throws IOException {
077        if (len == 0) {
078            return 0;
079        }
080        final int ret = in.read(b, off, len);
081        if (ret >= 0) {
082            checksum.update(b, off, ret);
083        }
084        return ret;
085    }
086
087    @Override
088    public long skip(final long n) throws IOException {
089        // Can't really skip, we have to hash everything to verify the checksum
090        if (read() >= 0) {
091            return 1;
092        }
093        return 0;
094    }
095
096    /**
097     * Returns the calculated checksum.
098     * @return the calculated checksum.
099     */
100    public long getValue() {
101        return checksum.getValue();
102    }
103
104}