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TrueZIP is a Java based Virtual File System (VFS) to enable transparent, multi-threaded read/write access to archive files (ZIP, TAR etc.) as if they were directories. Archive files may be arbitrarily nested and the nesting level is only limited by heap and file system size.

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/*
 * Copyright (C) 2009-2010 Schlichtherle IT Services
 *
 * Licensed 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,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package de.schlichtherle.io.archive.zip;

import de.schlichtherle.io.archive.spi.ArchiveEntry;
import de.schlichtherle.io.rof.ReadOnlyFile;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.util.zip.ZipException;

/**
 * A {@link ZipInputArchive} which checks the CRC-32 value for all ZIP entries.
 * The additional CRC-32 computation makes this class slower than its super
 * class.
 * 
 * If there is a mismatch of the CRC-32 values for a ZIP entry in an input
 * archive, the {@link java.io.InputStream#close} method of the corresponding
 * stream for the archive entry will throw a
 * {@link de.schlichtherle.util.zip.CRC32Exception}.
 * This exception is then propagated through the stack up to the corresponding
 * file operation in the package {@code de.schlichtherle.io} where it is
 * either allowed to pass on or is catched and processed accordingly.
 * For example, the {@link de.schlichtherle.io.FileInputStream#close()}
 * method would allow the {@code CRC32Exception} to pass on to the
 * client application, whereas the
 * {@link de.schlichtherle.io.File#catTo(OutputStream)} method would simply
 * return {@code false}.
 * Other than this, the archive entry will be processed normally.
 * So if just the CRC-32 value for the entry in the archive file has been
 * modified, you can still read its entire contents.
 * 
 * @see ZipInputArchive
 * @see CheckedZipDriver
 * @author Christian Schlichtherle
 * @version $Id: CheckedZipInputArchive.java,v 1.4 2010/08/20 13:09:51 christian_schlichtherle Exp $
 * @since TrueZIP 6.1
 */
public class CheckedZipInputArchive extends ZipInputArchive {
    
    public CheckedZipInputArchive(
            ReadOnlyFile rof,
            String charset,
            boolean preambled,
            boolean postambled)
    throws  NullPointerException,
            UnsupportedEncodingException,
            FileNotFoundException,
            ZipException,
            IOException {
        super(rof, charset, preambled, postambled);
    }

    /**
     * Overridden to read from a checked input stream.
     */
    public InputStream getInputStream(
            ArchiveEntry entry,
            ArchiveEntry dstEntry)
    throws  IOException {
        return super.getInputStream(
                entry.getName(), true, !(dstEntry instanceof ZipEntry));
    }
}