001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.net.io;
019
020import org.apache.commons.net.util.ListenerList;
021
022/**
023 * The CopyStreamAdapter will relay CopyStreamEvents to a list of listeners when either of its bytesTransferred() methods are called. Its purpose is to
024 * 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
025 * listeners. The static copyStream() methods invoke the bytesTransfered(long, int) of a CopyStreamListener for performance reasons and also because multiple
026 * listeners cannot be registered given that the methods are static.
027 *
028 * @see CopyStreamEvent
029 * @see CopyStreamListener
030 * @see Util
031 */
032public class CopyStreamAdapter implements CopyStreamListener {
033
034    private final ListenerList<CopyStreamListener> listeners;
035
036    /**
037     * Creates a new CopyStreamListener.
038     */
039    public CopyStreamAdapter() {
040        listeners = new ListenerList<>();
041    }
042
043    /**
044     * Adds a CopyStreamListener to receive CopyStreamEvents. Although this method is not declared to be synchronized, it is implemented in a thread safe
045     * manner.
046     *
047     * @param listener The CopyStreamlistener to register.
048     */
049    public void addCopyStreamListener(final CopyStreamListener listener) {
050        listeners.addListener(listener);
051    }
052
053    /**
054     * 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
055     * 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
056     * listeners, listing itself as the source of the event.
057     *
058     * @param event The CopyStreamEvent fired by the copying of a block of bytes.
059     */
060    @Override
061    public void bytesTransferred(final CopyStreamEvent event) {
062        listeners.forEach(listener -> listener.bytesTransferred(event));
063    }
064
065    /**
066     * 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
067     * after a block of bytes to inform the listener of the transfer. The CopyStreamAdapater will create a CopyStreamEvent from the arguments and relay the
068     * event to all of its registered listeners, listing itself as the source of the event.
069     *
070     * @param totalBytesTransferred The total number of bytes transferred so far by the copy operation.
071     * @param bytesTransferred      The number of bytes copied by the most recent write.
072     * @param streamSize            The number of bytes in the stream being copied. This may be equal to CopyStreamEvent.UNKNOWN_STREAM_SIZE if the size is
073     *                              unknown.
074     */
075    @Override
076    public void bytesTransferred(final long totalBytesTransferred, final int bytesTransferred, final long streamSize) {
077        listeners.forEach(listener -> listener.bytesTransferred(totalBytesTransferred, bytesTransferred, streamSize));
078    }
079
080    /**
081     * Removes a CopyStreamListener. Although this method is not synchronized, it is implemented in a thread safe manner.
082     *
083     * @param listener The CopyStreamlistener to unregister.
084     */
085    public void removeCopyStreamListener(final CopyStreamListener listener) {
086        listeners.removeListener(listener);
087    }
088}