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