    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.IOException;
    020import java.io.InputStream;
    021import java.util.zip.CheckedInputStream;
    022import java.util.zip.Checksum;
    023
    024/**
    025 * Verifies the checksum of the data read once the stream is exhausted.
    026 *
    027 * @NotThreadSafe
    028 * @since 1.7
    029 */
    030public class ChecksumVerifyingInputStream extends CheckedInputStream {
    031    // TODO Use Commons IO 2.16.0 ChecksumInputStream
    032
    033    private long remaining;
    034    private final long expected;
    035
    036    /**
    037     * Constructs a new instance.
    038     *
    039     * @param checksum         Checksum implementation.
    040     * @param in               the stream to wrap
    041     * @param size             the of the stream's content
    042     * @param expectedChecksum the expected checksum
    043     */
    044    public ChecksumVerifyingInputStream(final Checksum checksum, final InputStream in, final long size, final long expectedChecksum) {
    045        super(in, checksum);
    046        this.expected = expectedChecksum;
    047        this.remaining = size;
    048    }
    049
    050    /**
    051     * Gets the byte count remaining to read.
    052     *
    053     * @return bytes remaining to read.
    054     * @since 1.21
    055     */
    056    public long getBytesRemaining() {
    057        return remaining;
    058    }
    059
    060    /**
    061     * Reads a single byte from the stream
    062     *
    063     * @throws IOException if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
    064     */
    065    @Override
    066    public int read() throws IOException {
    067        if (remaining <= 0) {
    068            return -1;
    069        }
    070        final int data = super.read();
    071        if (data >= 0) {
    072            --remaining;
    073        }
    074        verify();
    075        return data;
    076    }
    077
    078    /**
    079     * Reads from the stream into a byte array.
    080     *
    081     * @throws IOException if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
    082     */
    083    @Override
    084    public int read(final byte[] b, final int off, final int len) throws IOException {
    085        if (len == 0) {
    086            return 0;
    087        }
    088        final int readCount = super.read(b, off, len);
    089        if (readCount >= 0) {
    090            remaining -= readCount;
    091        }
    092        verify();
    093        return readCount;
    094    }
    095
    096    private void verify() throws IOException {
    097        if (remaining <= 0 && expected != getChecksum().getValue()) {
    098            throw new IOException("Checksum verification failed");
    099        }
    100    }
    101}