src/main/java/org/apache/commons/net/io/CopyStreamAdapter.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * 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,
 * 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 org.apache.commons.net.io;

import java.util.EventListener;

import org.apache.commons.net.util.ListenerList;

/**
 * The CopyStreamAdapter will relay CopyStreamEvents to a list of listeners
 * when either of its bytesTransferred() methods are called.  Its purpose
 * is to facilitate the notification of the progress of a copy operation
 * performed by one of the static copyStream() methods in
 * org.apache.commons.io.Util to multiple listeners.  The static
 * copyStream() methods invoke the
 * bytesTransfered(long, int) of a CopyStreamListener for performance
 * reasons and also because multiple listeners cannot be registered given
 * that the methods are static.
 *
 *
 * @see CopyStreamEvent
 * @see CopyStreamListener
 * @see Util
 */
public class CopyStreamAdapter implements CopyStreamListener
{
    private final ListenerList internalListeners;

    /**
     * Creates a new copyStreamAdapter.
     */
    public CopyStreamAdapter()
    {
        internalListeners = new ListenerList();
    }

    /**
     * This method is invoked by a CopyStreamEvent source after copying
     * a block of bytes from a stream.  The CopyStreamEvent will contain
     * the total number of bytes transferred so far and the number of bytes
     * transferred in the last write.  The CopyStreamAdapater will relay
     * the event to all of its registered listeners, listing itself as the
     * source of the event.
     * @param event The CopyStreamEvent fired by the copying of a block of
     *              bytes.
     */
    @Override
    public void bytesTransferred(CopyStreamEvent event)
    {
        for (EventListener listener : internalListeners)
        {
            ((CopyStreamListener) (listener)).bytesTransferred(event);
        }
    }

    /**
     * This method is not part of the JavaBeans model and is used by the
     * static methods in the org.apache.commons.io.Util class for efficiency.
     * It is invoked after a block of bytes to inform the listener of the
     * transfer.  The CopyStreamAdapater will create a CopyStreamEvent
     * from the arguments and relay the event to all of its registered
     * listeners, listing itself as the source of the event.
     * @param totalBytesTransferred  The total number of bytes transferred
     *         so far by the copy operation.
     * @param bytesTransferred  The number of bytes copied by the most recent
     *          write.
     * @param streamSize The number of bytes in the stream being copied.
     *        This may be equal to CopyStreamEvent.UNKNOWN_STREAM_SIZE if
     *        the size is unknown.
     */
    @Override
    public void bytesTransferred(long totalBytesTransferred,
                                 int bytesTransferred, long streamSize)
    {
        for (EventListener listener : internalListeners)
        {
            ((CopyStreamListener) (listener)).bytesTransferred(
                    totalBytesTransferred, bytesTransferred, streamSize);
        }
    }

    /**
     * Registers a CopyStreamListener to receive CopyStreamEvents.
     * Although this method is not declared to be synchronized, it is
     * implemented in a thread safe manner.
     * @param listener  The CopyStreamlistener to register.
     */
    public void addCopyStreamListener(CopyStreamListener listener)
    {
        internalListeners.addListener(listener);
    }

    /**
     * Unregisters a CopyStreamListener.  Although this method is not
     * synchronized, it is implemented in a thread safe manner.
     * @param listener  The CopyStreamlistener to unregister.
     */
    public void removeCopyStreamListener(CopyStreamListener listener)
    {
        internalListeners.removeListener(listener);
    }
}