001/**
002 *
003 * Copyright 2003-2007 Jive Software.
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *     http://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 */
017package org.jivesoftware.smack.util;
018
019import java.io.IOException;
020import java.io.Writer;
021import java.util.ArrayList;
022import java.util.List;
023
024/**
025 * An ObservableWriter is a wrapper on a Writer that notifies to its listeners when
026 * writing to character streams.
027 * 
028 * @author Gaston Dombiak
029 */
030public class ObservableWriter extends Writer {
031    private static final int MAX_STRING_BUILDER_SIZE = 4096;
032
033    Writer wrappedWriter = null;
034    final List<WriterListener> listeners = new ArrayList<WriterListener>();
035    private final StringBuilder stringBuilder = new StringBuilder(MAX_STRING_BUILDER_SIZE);
036
037    public ObservableWriter(Writer wrappedWriter) {
038        this.wrappedWriter = wrappedWriter;
039    }
040
041    @Override
042    public void write(char[] cbuf, int off, int len) throws IOException {
043        wrappedWriter.write(cbuf, off, len);
044        String str = new String(cbuf, off, len);
045        maybeNotifyListeners(str);
046    }
047
048    @Override
049    public void flush() throws IOException {
050        notifyListeners();
051        wrappedWriter.flush();
052    }
053
054    @Override
055    public void close() throws IOException {
056        wrappedWriter.close();
057    }
058
059    @Override
060    public void write(int c) throws IOException {
061        wrappedWriter.write(c);
062    }
063
064    @Override
065    public void write(char[] cbuf) throws IOException {
066        wrappedWriter.write(cbuf);
067        String str = new String(cbuf);
068        maybeNotifyListeners(str);
069    }
070
071    @Override
072    public void write(String str) throws IOException {
073        wrappedWriter.write(str);
074        maybeNotifyListeners(str);
075    }
076
077    @Override
078    public void write(String str, int off, int len) throws IOException {
079        wrappedWriter.write(str, off, len);
080        str = str.substring(off, off + len);
081        maybeNotifyListeners(str);
082    }
083
084    private void maybeNotifyListeners(String s) {
085        stringBuilder.append(s);
086        if (stringBuilder.length() > MAX_STRING_BUILDER_SIZE) {
087            notifyListeners();
088        }
089    }
090
091    /**
092     * Notify that a new string has been written.
093     * 
094     * @param str the written String to notify 
095     */
096    private void notifyListeners() {
097        WriterListener[] writerListeners = null;
098        synchronized (listeners) {
099            writerListeners = new WriterListener[listeners.size()];
100            listeners.toArray(writerListeners);
101        }
102        String str = stringBuilder.toString();
103        stringBuilder.setLength(0);
104        for (int i = 0; i < writerListeners.length; i++) {
105            writerListeners[i].write(str);
106        }
107    }
108
109    /**
110     * Adds a writer listener to this writer that will be notified when
111     * new strings are sent.
112     *
113     * @param writerListener a writer listener.
114     */
115    public void addWriterListener(WriterListener writerListener) {
116        if (writerListener == null) {
117            return;
118        }
119        synchronized (listeners) {
120            if (!listeners.contains(writerListener)) {
121                listeners.add(writerListener);
122            }
123        }
124    }
125
126    /**
127     * Removes a writer listener from this writer.
128     *
129     * @param writerListener a writer listener.
130     */
131    public void removeWriterListener(WriterListener writerListener) {
132        synchronized (listeners) {
133            listeners.remove(writerListener);
134        }
135    }
136
137}