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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) 2006-2010 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.spi;

import de.schlichtherle.io.File;

import java.io.IOException;

/**
 * May be thrown by archive drivers to indicate that an {@link IOException}
 * occured as a transient event when accessing an archive file and another
 * try to access the same archive file may finally succeed.
 * On the other hand, if the archive controller catches an IOException from
 * an an archive driver when trying to access an archive file which is
 * not a {@code TransientIOException}, then the archive
 * controller may consider the archive file to be a false positive and cache
 * the exception until {@link File#umount} or {@link File#update} is called.
 * 
 * This feature is primarily used by the RAES encrypted ZIP file driver
 * family when prompting for passwords has been cancelled by the user.
 * In this case, the driver will wrap the {@code IOException} in a
 * {@code TransientIOException} and throw this instead to signal that
 * another attempt to prompt the user should be allowed.
 * 
 * This class is marked final since the archive controller will throw
 * away this exception anyway and deal with the transient cause only.
 *
 * @author Christian Schlichtherle
 * @version $Id: TransientIOException.java,v 1.4 2010/08/20 13:09:48 christian_schlichtherle Exp $
 * @since TrueZIP 6.4
 */
public final class TransientIOException extends IOException {

    /**
     * @param cause The transient cause of this exception.
     * @throws NullPointerException If {@code cause} is {@code null}.
     */
    public TransientIOException(IOException cause) {
        if (cause == null)
            throw new NullPointerException();
        super.initCause(cause);
    }

    /**
     * Returns the transient cause of this exception as an
     * {@code IOException} - {@code null} is never returned.
     */
    public IOException getTransientCause() {
        return (IOException) getCause();
    }
}