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The file system driver family for ZIP and related archive file types. Add the JAR artifact of this module to the run time class path to make its file system drivers available for service location in the client API modules.

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/*
 * Copyright (C) 2005-2013 Schlichtherle IT Services.
 * All rights reserved. Use is subject to license terms.
 */
package de.schlichtherle.truezip.zip;

import java.io.IOException;
import java.io.InputStream;
import java.util.zip.CRC32;
import java.util.zip.CheckedInputStream;

/**
 * Compares the CRC computed from the content to the CRC in the ZIP entry
 * and throws a CRC32Exception if it detects a mismatch in its method
 * {@link #close()}.
 *
 * @author Christian Schlichtherle
 */
final class Crc32InputStream extends CheckedInputStream {
    private final ZipEntry entry;
    private final int size;
    boolean closed;

    Crc32InputStream(
            final InputStream in,
            final ZipEntry entry,
            final int size) {
        super(in, new CRC32());
        this.entry = entry;
        this.size = size;
    }

    /**
     * This method skips {@code toSkip} bytes in the given input stream
     * using the given buffer unless EOF or IOException.
     */
    @Override
    public long skip(long toSkip) throws IOException {
        long total = 0;
        final byte[] buf = new byte[size];
        for (long len; (len = toSkip - total) > 0; total += len) {
            len = read(buf, 0, len < buf.length ? (int) len : buf.length);
            if (len < 0) {
                break;
            }
        }
        return total;
    }

    @Override
    public void close() throws IOException {
        if (!closed) {
            while (skip(Long.MAX_VALUE) > 0) {
                // process CRC-32 until EOF
            }
        }
        super.close();
        closed = true;
        final long expected = entry.getCrc();
        final long computed = getChecksum().getValue();
        if (expected != computed)
            throw new CRC32Exception(entry.getName(), expected, computed);
    }
}