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1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package org.jboss.netty.handler.codec.http;
17  
18  import org.jboss.netty.buffer.ChannelBuffer;
19  import org.jboss.netty.handler.codec.compression.JdkZlibEncoder;
20  import org.jboss.netty.handler.codec.compression.ZlibEncoder;
21  import org.jboss.netty.handler.codec.compression.ZlibWrapper;
22  import org.jboss.netty.handler.codec.embedder.EncoderEmbedder;
23  import org.jboss.netty.util.internal.DetectionUtil;
24  
25  /**
26   * Compresses an {@link HttpMessage} and an {@link HttpChunk} in {@code gzip} or
27   * {@code deflate} encoding while respecting the {@code "Accept-Encoding"} header.
28   * If there is no matching encoding, no compression is done.  For more
29   * information on how this handler modifies the message, please refer to
30   * {@link HttpContentEncoder}.
31   */
32  public class HttpContentCompressor extends HttpContentEncoder {
33  
34      private final int compressionLevel;
35      private final int windowBits;
36      private final int memLevel;
37  
38      /**
39       * Creates a new handler with the default compression level (<tt>6</tt>),
40       * default window size (<tt>15</tt>) and default memory level (<tt>8</tt>).
41       */
42      public HttpContentCompressor() {
43          this(6);
44      }
45  
46      /**
47       * Creates a new handler with the specified compression level, default
48       * window size (<tt>15</tt>) and default memory level (<tt>8</tt>).
49       *
50       * @param compressionLevel
51       *        {@code 1} yields the fastest compression and {@code 9} yields the
52       *        best compression.  {@code 0} means no compression.  The default
53       *        compression level is {@code 6}.
54       */
55      public HttpContentCompressor(int compressionLevel) {
56          this(compressionLevel, 15, 8);
57      }
58  
59      /**
60       * Creates a new handler with the specified compression level, window size,
61       * and memory level..
62       *
63       * @param compressionLevel
64       *        {@code 1} yields the fastest compression and {@code 9} yields the
65       *        best compression.  {@code 0} means no compression.  The default
66       *        compression level is {@code 6}.
67       * @param windowBits
68       *        The base two logarithm of the size of the history buffer.  The
69       *        value should be in the range {@code 9} to {@code 15} inclusive.
70       *        Larger values result in better compression at the expense of
71       *        memory usage.  The default value is {@code 15}.
72       * @param memLevel
73       *        How much memory should be allocated for the internal compression
74       *        state.  {@code 1} uses minimum memory and {@code 9} uses maximum
75       *        memory.  Larger values result in better and faster compression
76       *        at the expense of memory usage.  The default value is {@code 8}
77       */
78      public HttpContentCompressor(int compressionLevel, int windowBits, int memLevel) {
79          if (compressionLevel < 0 || compressionLevel > 9) {
80              throw new IllegalArgumentException(
81                      "compressionLevel: " + compressionLevel + " (expected: 0-9)");
82          }
83          if (windowBits < 9 || windowBits > 15) {
84              throw new IllegalArgumentException(
85                      "windowBits: " + windowBits + " (expected: 9-15)");
86          }
87          if (memLevel < 1 || memLevel > 9) {
88              throw new IllegalArgumentException(
89                      "memLevel: " + memLevel + " (expected: 1-9)");
90          }
91          this.compressionLevel = compressionLevel;
92          this.windowBits = windowBits;
93          this.memLevel = memLevel;
94      }
95  
96      @Override
97      protected EncoderEmbedder<ChannelBuffer> newContentEncoder(
98              HttpMessage msg, String acceptEncoding) throws Exception {
99          String contentEncoding = msg.getHeader(HttpHeaders.Names.CONTENT_ENCODING);
100         if (contentEncoding != null &&
101             !HttpHeaders.Values.IDENTITY.equalsIgnoreCase(contentEncoding)) {
102             // Encoded already.
103             return null;
104         }
105 
106         ZlibWrapper wrapper = determineWrapper(acceptEncoding);
107         if (wrapper == null) {
108             return null;
109         }
110 
111         if (DetectionUtil.javaVersion() >= 7) {
112             return new EncoderEmbedder<ChannelBuffer>(
113                     new JdkZlibEncoder(wrapper, compressionLevel));
114         } else {
115             return new EncoderEmbedder<ChannelBuffer>(
116                     new ZlibEncoder(wrapper, compressionLevel, windowBits, memLevel));
117         }
118     }
119 
120     @Override
121     protected String getTargetContentEncoding(String acceptEncoding) throws Exception {
122         ZlibWrapper wrapper = determineWrapper(acceptEncoding);
123         if (wrapper == null) {
124             return null;
125         }
126 
127         switch (wrapper) {
128         case GZIP:
129             return "gzip";
130         case ZLIB:
131             return "deflate";
132         default:
133             throw new Error();
134         }
135     }
136 
137     private static ZlibWrapper determineWrapper(String acceptEncoding) {
138         float starQ = -1.0f;
139         float gzipQ = -1.0f;
140         float deflateQ = -1.0f;
141         for (String encoding : acceptEncoding.split(",")) {
142             float q = 1.0f;
143             int equalsPos = encoding.indexOf('=');
144             if (equalsPos != -1) {
145                 try {
146                     q = Float.valueOf(encoding.substring(equalsPos + 1));
147                 } catch (NumberFormatException e) {
148                     // Ignore encoding
149                     q = 0.0f;
150                 }
151             }
152             if (encoding.indexOf("*") >= 0) {
153                 starQ = q;
154             } else if (encoding.indexOf("gzip") >= 0 && q > gzipQ) {
155                 gzipQ = q;
156             } else if (encoding.indexOf("deflate") >= 0 && q > deflateQ) {
157                 deflateQ = q;
158             }
159         }
160         if (gzipQ > 0.0f || deflateQ > 0.0f) {
161             if (gzipQ >= deflateQ) {
162                 return ZlibWrapper.GZIP;
163             } else {
164                 return ZlibWrapper.ZLIB;
165             }
166         }
167         if (starQ > 0.0f) {
168             if (gzipQ == -1.0f) {
169                 return ZlibWrapper.GZIP;
170             }
171             if (deflateQ == -1.0f) {
172                 return ZlibWrapper.ZLIB;
173             }
174         }
175         return null;
176     }
177 }