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.compression;
21
22 import java.io.IOException;
23
24 import org.apache.mina.core.buffer.IoBuffer;
25 import org.apache.mina.core.filterchain.IoFilter;
26 import org.apache.mina.core.filterchain.IoFilterChain;
27 import org.apache.mina.core.session.AttributeKey;
28 import org.apache.mina.core.session.IoSession;
29 import org.apache.mina.core.write.WriteRequest;
30 import org.apache.mina.filter.util.WriteRequestFilter;
31
32 /**
33 * An {@link IoFilter} which compresses all data using
34 * <a href="http://www.jcraft.com/jzlib/">JZlib</a>.
35 * Support for the LZW (DLCZ) algorithm is also planned.
36 * <p>
37 * This filter only supports compression using the <tt>PARTIAL FLUSH</tt> method,
38 * since that is the only method useful when doing stream level compression.
39 * <p>
40 * This filter supports compression/decompression of the input and output
41 * channels selectively. It can also be enabled/disabled on the fly.
42 * <p>
43 * This filter does not discard the zlib objects, keeping them around for the
44 * entire life of the filter. This is because the zlib dictionary needs to
45 * be built up over time, which is used during compression and decompression.
46 * Over time, as repetitive data is sent over the wire, the compression efficiency
47 * steadily increases.
48 * <p>
49 * Note that the zlib header is written only once. It is not necessary that
50 * the data received after processing by this filter may not be complete due
51 * to packet fragmentation.
52 * <p>
53 * It goes without saying that the other end of this stream should also have a
54 * compatible compressor/decompressor using the same algorithm.
55 *
56 * @author The Apache MINA Project (dev@mina.apache.org)
57 * @version $Rev: 671827 $, $Date: 2008-06-26 10:49:48 +0200 (jeu, 26 jun 2008) $
58 */
59 public class CompressionFilter extends WriteRequestFilter {
60 /**
61 * Max compression level. Will give the highest compression ratio, but
62 * will also take more cpu time and is the slowest.
63 */
64 public static final int COMPRESSION_MAX = Zlib.COMPRESSION_MAX;
65
66 /**
67 * Provides the best speed at the price of a low compression ratio.
68 */
69 public static final int COMPRESSION_MIN = Zlib.COMPRESSION_MIN;
70
71 /**
72 * No compression done on the data.
73 */
74 public static final int COMPRESSION_NONE = Zlib.COMPRESSION_NONE;
75
76 /**
77 * The default compression level used. Provides the best balance
78 * between speed and compression
79 */
80 public static final int COMPRESSION_DEFAULT = Zlib.COMPRESSION_DEFAULT;
81
82 /**
83 * A session attribute that stores the {@link Zlib} object used for compression.
84 */
85 private final AttributeKey DEFLATER = new AttributeKey(getClass(), "deflater");
86
87 /**
88 * A session attribute that stores the {@link Zlib} object used for decompression.
89 */
90 private final AttributeKey INFLATER = new AttributeKey(getClass(), "inflater");
91
92 /**
93 * A flag that allows you to disable compression once.
94 */
95 public static final AttributeKey DISABLE_COMPRESSION_ONCE = new AttributeKey(CompressionFilter.class, "disableOnce");
96
97 private boolean compressInbound = true;
98
99 private boolean compressOutbound = true;
100
101 private int compressionLevel;
102
103 /**
104 * Creates a new instance which compresses outboud data and decompresses
105 * inbound data with default compression level.
106 */
107 public CompressionFilter() {
108 this(true, true, COMPRESSION_DEFAULT);
109 }
110
111 /**
112 * Creates a new instance which compresses outboud data and decompresses
113 * inbound data with the specified <tt>compressionLevel</tt>.
114 *
115 * @param compressionLevel the level of compression to be used. Must
116 * be one of {@link #COMPRESSION_DEFAULT},
117 * {@link #COMPRESSION_MAX},
118 * {@link #COMPRESSION_MIN}, and
119 * {@link #COMPRESSION_NONE}.
120 */
121 public CompressionFilter(final int compressionLevel) {
122 this(true, true, compressionLevel);
123 }
124
125 /**
126 * Creates a new instance.
127 *
128 * @param compressInbound <tt>true</tt> if data read is to be decompressed
129 * @param compressOutbound <tt>true</tt> if data written is to be compressed
130 * @param compressionLevel the level of compression to be used. Must
131 * be one of {@link #COMPRESSION_DEFAULT},
132 * {@link #COMPRESSION_MAX},
133 * {@link #COMPRESSION_MIN}, and
134 * {@link #COMPRESSION_NONE}.
135 */
136 public CompressionFilter(final boolean compressInbound,
137 final boolean compressOutbound, final int compressionLevel) {
138 this.compressionLevel = compressionLevel;
139 this.compressInbound = compressInbound;
140 this.compressOutbound = compressOutbound;
141 }
142
143 @Override
144 public void messageReceived(NextFilter nextFilter, IoSession session,
145 Object message) throws Exception {
146 if (!compressInbound || !(message instanceof IoBuffer)) {
147 nextFilter.messageReceived(session, message);
148 return;
149 }
150
151 Zlib inflater = (Zlib) session.getAttribute(INFLATER);
152 if (inflater == null) {
153 throw new IllegalStateException();
154 }
155
156 IoBuffer inBuffer = (IoBuffer) message;
157 IoBuffer outBuffer = inflater.inflate(inBuffer);
158 nextFilter.messageReceived(session, outBuffer);
159 }
160
161 /*
162 * @see org.apache.mina.core.IoFilter#filterWrite(org.apache.mina.core.IoFilter.NextFilter, org.apache.mina.core.IoSession, org.apache.mina.core.IoFilter.WriteRequest)
163 */
164 @Override
165 protected Object doFilterWrite(
166 NextFilter nextFilter, IoSession session,
167 WriteRequest writeRequest) throws IOException {
168 if (!compressOutbound) {
169 return null;
170 }
171
172 if (session.containsAttribute(DISABLE_COMPRESSION_ONCE)) {
173 // Remove the marker attribute because it is temporary.
174 session.removeAttribute(DISABLE_COMPRESSION_ONCE);
175 return null;
176 }
177
178 Zlib deflater = (Zlib) session.getAttribute(DEFLATER);
179 if (deflater == null) {
180 throw new IllegalStateException();
181 }
182
183 IoBuffer inBuffer = (IoBuffer) writeRequest.getMessage();
184 if (!inBuffer.hasRemaining()) {
185 // Ignore empty buffers
186 return null;
187 } else {
188 return deflater.deflate(inBuffer);
189 }
190 }
191
192 @Override
193 public void onPreAdd(IoFilterChain parent, String name,
194 NextFilter nextFilter) throws Exception {
195 if (parent.contains(CompressionFilter.class)) {
196 throw new IllegalStateException(
197 "Only one " + CompressionFilter.class + " is permitted.");
198 }
199
200 Zlib deflater = new Zlib(compressionLevel, Zlib.MODE_DEFLATER);
201 Zlib inflater = new Zlib(compressionLevel, Zlib.MODE_INFLATER);
202
203 IoSession session = parent.getSession();
204
205 session.setAttribute(DEFLATER, deflater);
206 session.setAttribute(INFLATER, inflater);
207 }
208
209 /**
210 * Returns <tt>true</tt> if incoming data is being compressed.
211 */
212 public boolean isCompressInbound() {
213 return compressInbound;
214 }
215
216 /**
217 * Sets if incoming data has to be compressed.
218 */
219 public void setCompressInbound(boolean compressInbound) {
220 this.compressInbound = compressInbound;
221 }
222
223 /**
224 * Returns <tt>true</tt> if the filter is compressing data being written.
225 */
226 public boolean isCompressOutbound() {
227 return compressOutbound;
228 }
229
230 /**
231 * Set if outgoing data has to be compressed.
232 */
233 public void setCompressOutbound(boolean compressOutbound) {
234 this.compressOutbound = compressOutbound;
235 }
236
237 @Override
238 public void onPostRemove(IoFilterChain parent, String name,
239 NextFilter nextFilter) throws Exception {
240 super.onPostRemove(parent, name, nextFilter);
241 IoSession session = parent.getSession();
242 if (session == null) {
243 return;
244 }
245
246 Zlib inflater = (Zlib) session.getAttribute(INFLATER);
247 Zlib deflater = (Zlib) session.getAttribute(DEFLATER);
248 if (deflater != null) {
249 deflater.cleanUp();
250 }
251
252 if (inflater != null) {
253 inflater.cleanUp();
254 }
255 }
256 }