1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.mina.filter;
21
22 import java.io.IOException;
23
24 import org.apache.mina.common.ByteBuffer;
25 import org.apache.mina.common.IoFilter;
26 import org.apache.mina.common.IoFilterAdapter;
27 import org.apache.mina.common.IoFilterChain;
28 import org.apache.mina.common.IoSession;
29 import org.apache.mina.filter.support.Zlib;
30
31 /**
32 * An {@link IoFilter} which compresses all data using
33 * <a href="http://www.jcraft.com/jzlib/">JZlib</a>.
34 * Support for the LZW (DLCZ) algorithm is also planned.
35 * <p>
36 * This filter only supports compression using the <tt>PARTIAL FLUSH</tt> method,
37 * since that is the only method useful when doing stream level compression.
38 * <p>
39 * This filter supports compression/decompression of the input and output
40 * channels selectively. It can also be enabled/disabled on the fly.
41 * <p>
42 * This filter does not discard the zlib objects, keeping them around for the
43 * entire life of the filter. This is because the zlib dictionary needs to
44 * be built up over time, which is used during compression and decompression.
45 * Over time, as repetitive data is sent over the wire, the compression efficiency
46 * steadily increases.
47 * <p>
48 * Note that the zlib header is written only once. It is not necessary that
49 * the data received after processing by this filter may not be complete due
50 * to packet fragmentation.
51 * <p>
52 * It goes without saying that the other end of this stream should also have a
53 * compatible compressor/decompressor using the same algorithm.
54 *
55 * @author The Apache Directory Project (mina-dev@directory.apache.org)
56 * @version $Rev: 629330 $, $Date: 2008-02-20 12:18:28 +0900 (Wed, 20 Feb 2008) $
57 */
58 public class CompressionFilter extends IoFilterAdapter {
59 /**
60 * Max compression level. Will give the highest compression ratio, but
61 * will also take more cpu time and is the slowest.
62 */
63 public static final int COMPRESSION_MAX = Zlib.COMPRESSION_MAX;
64
65 /**
66 * Provides the best speed at the price of a low compression ratio.
67 */
68 public static final int COMPRESSION_MIN = Zlib.COMPRESSION_MIN;
69
70 /**
71 * No compression done on the data.
72 */
73 public static final int COMPRESSION_NONE = Zlib.COMPRESSION_NONE;
74
75 /**
76 * The default compression level used. Provides the best balance
77 * between speed and compression
78 */
79 public static final int COMPRESSION_DEFAULT = Zlib.COMPRESSION_DEFAULT;
80
81 /**
82 * A session attribute that stores the {@link Zlib} object used for compression.
83 */
84 private static final String DEFLATER = CompressionFilter.class.getName()
85 + ".Deflater";
86
87 /**
88 * A session attribute that stores the {@link Zlib} object used for decompression.
89 */
90 private static final String INFLATER = CompressionFilter.class.getName()
91 + ".Inflater";
92
93 /**
94 * A flag that allows you to disable compression once.
95 */
96 public static final String DISABLE_COMPRESSION_ONCE = CompressionFilter.class
97 .getName()
98 + ".DisableCompressionOnce";
99
100 private boolean compressInbound = true;
101
102 private boolean compressOutbound = true;
103
104 private int compressionLevel;
105
106 /**
107 * Creates a new instance which compresses outboud data and decompresses
108 * inbound data with default compression level.
109 */
110 public CompressionFilter() {
111 this(true, true, COMPRESSION_DEFAULT);
112 }
113
114 /**
115 * Creates a new instance which compresses outboud data and decompresses
116 * inbound data with the specified <tt>compressionLevel</tt>.
117 *
118 * @param compressionLevel the level of compression to be used. Must
119 * be one of {@link #COMPRESSION_DEFAULT},
120 * {@link #COMPRESSION_MAX},
121 * {@link #COMPRESSION_MIN}, and
122 * {@link #COMPRESSION_NONE}.
123 */
124 public CompressionFilter(final int compressionLevel) {
125 this(true, true, compressionLevel);
126 }
127
128 /**
129 * Creates a new instance.
130 *
131 * @param compressInbound <tt>true</tt> if data read is to be decompressed
132 * @param compressOutbound <tt>true</tt> if data written is to be compressed
133 * @param compressionLevel the level of compression to be used. Must
134 * be one of {@link #COMPRESSION_DEFAULT},
135 * {@link #COMPRESSION_MAX},
136 * {@link #COMPRESSION_MIN}, and
137 * {@link #COMPRESSION_NONE}.
138 */
139 public CompressionFilter(final boolean compressInbound,
140 final boolean compressOutbound, final int compressionLevel) {
141 this.compressionLevel = compressionLevel;
142 this.compressInbound = compressInbound;
143 this.compressOutbound = compressOutbound;
144 }
145
146 public void messageReceived(NextFilter nextFilter, IoSession session,
147 Object message) throws Exception {
148 if (!compressInbound || !(message instanceof ByteBuffer)) {
149 nextFilter.messageReceived(session, message);
150 return;
151 }
152
153 Zlib inflater = (Zlib) session.getAttribute(INFLATER);
154 if (inflater == null) {
155 throw new IllegalStateException();
156 }
157
158 ByteBuffer inBuffer = (ByteBuffer) message;
159 ByteBuffer outBuffer = inflater.inflate(inBuffer);
160 inBuffer.release();
161 nextFilter.messageReceived(session, outBuffer);
162 }
163
164 /*
165 * @see org.apache.mina.common.IoFilter#filterWrite(org.apache.mina.common.IoFilter.NextFilter, org.apache.mina.common.IoSession, org.apache.mina.common.IoFilter.WriteRequest)
166 */
167 public void filterWrite(NextFilter nextFilter, IoSession session,
168 WriteRequest writeRequest) throws IOException {
169 if (!compressOutbound) {
170 nextFilter.filterWrite(session, writeRequest);
171 return;
172 }
173
174 if (session.containsAttribute(DISABLE_COMPRESSION_ONCE)) {
175 // Remove the marker attribute because it is temporary.
176 session.removeAttribute(DISABLE_COMPRESSION_ONCE);
177 nextFilter.filterWrite(session, writeRequest);
178 return;
179 }
180
181 Zlib deflater = (Zlib) session.getAttribute(DEFLATER);
182 if (deflater == null) {
183 throw new IllegalStateException();
184 }
185
186 ByteBuffer inBuffer = (ByteBuffer) writeRequest.getMessage();
187 if (!inBuffer.hasRemaining()) {
188 // Ignore empty buffers
189 nextFilter.filterWrite(session, writeRequest);
190 } else {
191 ByteBuffer outBuf = deflater.deflate(inBuffer);
192 inBuffer.release();
193 nextFilter.filterWrite(session, new WriteRequest(outBuf,
194 writeRequest.getFuture()));
195 }
196 }
197
198 public void onPreAdd(IoFilterChain parent, String name,
199 NextFilter nextFilter) throws Exception {
200 if (parent.contains(CompressionFilter.class)) {
201 throw new IllegalStateException(
202 "A filter chain cannot contain more than"
203 + " one Stream Compression filter.");
204 }
205
206 Zlib deflater = new Zlib(compressionLevel, Zlib.MODE_DEFLATER);
207 Zlib inflater = new Zlib(compressionLevel, Zlib.MODE_INFLATER);
208
209 IoSession session = parent.getSession();
210
211 session.setAttribute(DEFLATER, deflater);
212 session.setAttribute(INFLATER, inflater);
213 }
214
215 /**
216 * Returns <tt>true</tt> if incoming data is being compressed.
217 */
218 public boolean isCompressInbound() {
219 return compressInbound;
220 }
221
222 /**
223 * Sets if incoming data has to be compressed.
224 */
225 public void setCompressInbound(boolean compressInbound) {
226 this.compressInbound = compressInbound;
227 }
228
229 /**
230 * Returns <tt>true</tt> if the filter is compressing data being written.
231 */
232 public boolean isCompressOutbound() {
233 return compressOutbound;
234 }
235
236 /**
237 * Set if outgoing data has to be compressed.
238 */
239 public void setCompressOutbound(boolean compressOutbound) {
240 this.compressOutbound = compressOutbound;
241 }
242
243 public void onPostRemove(IoFilterChain parent, String name,
244 NextFilter nextFilter) throws Exception {
245 super.onPostRemove(parent, name, nextFilter);
246 IoSession session = parent.getSession();
247 if (session == null) {
248 return;
249 }
250
251 Zlib inflater = (Zlib) session.getAttribute(INFLATER);
252 Zlib deflater = (Zlib) session.getAttribute(DEFLATER);
253 if (deflater != null) {
254 deflater.cleanUp();
255 }
256
257 if (inflater != null) {
258 inflater.cleanUp();
259 }
260 }
261 }