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    private void notifyListeners() {
095        WriterListener[] writerListeners;
096        synchronized (listeners) {
097            writerListeners = new WriterListener[listeners.size()];
098            listeners.toArray(writerListeners);
099        }
100        String str = stringBuilder.toString();
101        stringBuilder.setLength(0);
102        for (WriterListener writerListener : writerListeners) {
103            writerListener.write(str);
104        }
105    }
106
107    /**
108     * Adds a writer listener to this writer that will be notified when
109     * new strings are sent.
110     *
111     * @param writerListener a writer listener.
112     */
113    public void addWriterListener(WriterListener writerListener) {
114        if (writerListener == null) {
115            return;
116        }
117        synchronized (listeners) {
118            if (!listeners.contains(writerListener)) {
119                listeners.add(writerListener);
120            }
121        }
122    }
123
124    /**
125     * Removes a writer listener from this writer.
126     *
127     * @param writerListener a writer listener.
128     */
129    public void removeWriterListener(WriterListener writerListener) {
130        synchronized (listeners) {
131            listeners.remove(writerListener);
132        }
133    }
134
135}