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 *      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.apache.activemq.transport.nio;
018
019import java.io.EOFException;
020import java.io.IOException;
021import java.io.InterruptedIOException;
022import java.io.OutputStream;
023import java.nio.ByteBuffer;
024import java.nio.channels.WritableByteChannel;
025
026import org.apache.activemq.transport.tcp.TimeStampStream;
027
028/**
029 * An optimized buffered outputstream for Tcp
030 * 
031 * 
032 */
033
034public class NIOOutputStream extends OutputStream implements TimeStampStream {
035
036    private static final int BUFFER_SIZE = 8192;
037
038    private final WritableByteChannel out;
039    private final byte[] buffer;
040    private final ByteBuffer byteBuffer;
041
042    private int count;
043    private boolean closed;
044    private volatile long writeTimestamp = -1;//concurrent reads of this value
045
046    /**
047     * Constructor
048     * 
049     * @param out
050     */
051    public NIOOutputStream(WritableByteChannel out) {
052        this(out, BUFFER_SIZE);
053    }
054
055    /**
056     * Creates a new buffered output stream to write data to the specified
057     * underlying output stream with the specified buffer size.
058     * 
059     * @param out the underlying output stream.
060     * @param size the buffer size.
061     * @throws IllegalArgumentException if size <= 0.
062     */
063    public NIOOutputStream(WritableByteChannel out, int size) {
064        this.out = out;
065        if (size <= 0) {
066            throw new IllegalArgumentException("Buffer size <= 0");
067        }
068        buffer = new byte[size];
069        byteBuffer = ByteBuffer.wrap(buffer);
070    }
071
072    /**
073     * write a byte on to the stream
074     * 
075     * @param b - byte to write
076     * @throws IOException
077     */
078    public void write(int b) throws IOException {
079        checkClosed();
080        if (availableBufferToWrite() < 1) {
081            flush();
082        }
083        buffer[count++] = (byte)b;
084    }
085
086    /**
087     * write a byte array to the stream
088     * 
089     * @param b the byte buffer
090     * @param off the offset into the buffer
091     * @param len the length of data to write
092     * @throws IOException
093     */
094    public void write(byte b[], int off, int len) throws IOException {
095        checkClosed();
096        if (availableBufferToWrite() < len) {
097            flush();
098        }
099        if (buffer.length >= len) {
100            System.arraycopy(b, off, buffer, count, len);
101            count += len;
102        } else {
103            write(ByteBuffer.wrap(b, off, len));
104        }
105    }
106
107    /**
108     * flush the data to the output stream This doesn't call flush on the
109     * underlying outputstream, because Tcp is particularly efficent at doing
110     * this itself ....
111     * 
112     * @throws IOException
113     */
114    public void flush() throws IOException {
115        if (count > 0 && out != null) {
116            byteBuffer.position(0);
117            byteBuffer.limit(count);
118            write(byteBuffer);
119            count = 0;
120        }
121    }
122
123    /**
124     * close this stream
125     * 
126     * @throws IOException
127     */
128    public void close() throws IOException {
129        super.close();
130        closed = true;
131    }
132
133    /**
134     * Checks that the stream has not been closed
135     * 
136     * @throws IOException
137     */
138    protected void checkClosed() throws IOException {
139        if (closed) {
140            throw new EOFException("Cannot write to the stream any more it has already been closed");
141        }
142    }
143
144    /**
145     * @return the amount free space in the buffer
146     */
147    private int availableBufferToWrite() {
148        return buffer.length - count;
149    }
150
151    protected void write(ByteBuffer data) throws IOException {
152        int remaining = data.remaining();
153        int lastRemaining = remaining - 1;
154        long delay = 1;
155        try {
156            writeTimestamp = System.currentTimeMillis();
157            while (remaining > 0) {
158
159                // We may need to do a little bit of sleeping to avoid a busy loop.
160                // Slow down if no data was written out..
161                if (remaining == lastRemaining) {
162                    try {
163                        // Use exponential rollback to increase sleep time.
164                        Thread.sleep(delay);
165                        delay *= 2;
166                        if (delay > 1000) {
167                            delay = 1000;
168                        }
169                    } catch (InterruptedException e) {
170                        throw new InterruptedIOException();
171                    }
172                } else {
173                    delay = 1;
174                }
175                lastRemaining = remaining;
176
177                // Since the write is non-blocking, all the data may not have been
178                // written.
179                out.write(data);
180                remaining = data.remaining();
181            }
182        } finally {
183            writeTimestamp = -1;
184        }
185    }
186    
187    
188    /* (non-Javadoc)
189     * @see org.apache.activemq.transport.tcp.TimeStampStream#isWriting()
190     */
191    public boolean isWriting() {
192        return writeTimestamp > 0;
193    }
194    
195    /* (non-Javadoc)
196     * @see org.apache.activemq.transport.tcp.TimeStampStream#getWriteTimestamp()
197     */
198    public long getWriteTimestamp() {
199        return writeTimestamp;
200    }
201
202}