/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
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 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
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 *  See the License for the specific language governing permissions and
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package org.apache.commons.compress.utils;

import java.io.IOException;
import java.io.InputStream;
import java.util.zip.Checksum;

A stream that verifies the checksum of the data read once the stream is exhausted.
@NotThreadSafe
Since:1.7
/** * A stream that verifies the checksum of the data read once the stream is * exhausted. * @NotThreadSafe * @since 1.7 */
public class ChecksumVerifyingInputStream extends InputStream { private final InputStream in; private long bytesRemaining; private final long expectedChecksum; private final Checksum checksum; public ChecksumVerifyingInputStream(final Checksum checksum, final InputStream in, final long size, final long expectedChecksum) { this.checksum = checksum; this.in = in; this.expectedChecksum = expectedChecksum; this.bytesRemaining = size; }
Reads a single byte from the stream
Throws:
  • IOException – if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
/** * Reads a single byte from the stream * @throws IOException if the underlying stream throws or the * stream is exhausted and the Checksum doesn't match the expected * value */
@Override public int read() throws IOException { if (bytesRemaining <= 0) { return -1; } final int ret = in.read(); if (ret >= 0) { checksum.update(ret); --bytesRemaining; } if (bytesRemaining == 0 && expectedChecksum != checksum.getValue()) { throw new IOException("Checksum verification failed"); } return ret; }
Reads a byte array from the stream
Throws:
  • IOException – if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
/** * Reads a byte array from the stream * @throws IOException if the underlying stream throws or the * stream is exhausted and the Checksum doesn't match the expected * value */
@Override public int read(final byte[] b) throws IOException { return read(b, 0, b.length); }
Reads from the stream into a byte array.
Throws:
  • IOException – if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
/** * Reads from the stream into a byte array. * @throws IOException if the underlying stream throws or the * stream is exhausted and the Checksum doesn't match the expected * value */
@Override public int read(final byte[] b, final int off, final int len) throws IOException { if (len == 0) { return 0; } final int ret = in.read(b, off, len); if (ret >= 0) { checksum.update(b, off, ret); bytesRemaining -= ret; } if (bytesRemaining <= 0 && expectedChecksum != checksum.getValue()) { throw new IOException("Checksum verification failed"); } return ret; } @Override public long skip(final long n) throws IOException { // Can't really skip, we have to hash everything to verify the checksum if (read() >= 0) { return 1; } return 0; } @Override public void close() throws IOException { in.close(); } }