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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  
26  import com.jcraft.jzlib.JZlib;
27  import com.jcraft.jzlib.ZStream;
28  
29  /**
30   * A helper class for interfacing with the JZlib library. This class acts both
31   * as a compressor and decompressor, but only as one at a time.  The only
32   * flush method supported is <tt>Z_SYNC_FLUSH</tt> also known as <tt>Z_PARTIAL_FLUSH</tt>
33   *
34   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
35   */
36  class Zlib {
37      /** Try o get the best possible compression */
38      public static final int COMPRESSION_MAX = JZlib.Z_BEST_COMPRESSION;
39  
40      /** Favor speed over compression ratio */ 
41      public static final int COMPRESSION_MIN = JZlib.Z_BEST_SPEED;
42  
43      /** No compression */
44      public static final int COMPRESSION_NONE = JZlib.Z_NO_COMPRESSION;
45  
46      /** Default compression */
47      public static final int COMPRESSION_DEFAULT = JZlib.Z_DEFAULT_COMPRESSION;
48  
49      /** Compression mode */ 
50      public static final int MODE_DEFLATER = 1;
51  
52      /** Uncompress mode */ 
53      public static final int MODE_INFLATER = 2;
54  
55      /** The requested compression level */
56      private int compressionLevel;
57  
58      /** The inner stream used to inflate or deflate the data */
59      private ZStream zStream = null;
60  
61      /** The selected operation mode : INFLATE or DEFLATE */
62      private int mode = -1;
63  
64      /**
65       * Creates an instance of the ZLib class.
66       * 
67       * @param compressionLevel the level of compression that should be used. One of
68       * <tt>COMPRESSION_MAX</tt>, <tt>COMPRESSION_MIN</tt>,
69       * <tt>COMPRESSION_NONE</tt> or <tt>COMPRESSION_DEFAULT</tt>
70       * @param mode the mode in which the instance will operate. Can be either
71       * of <tt>MODE_DEFLATER</tt> or <tt>MODE_INFLATER</tt>
72       * @throws IllegalArgumentException if the mode is incorrect
73       */
74      public Zlib(int compressionLevel, int mode) {
75          switch (compressionLevel) {
76          case COMPRESSION_MAX:
77          case COMPRESSION_MIN:
78          case COMPRESSION_NONE:
79          case COMPRESSION_DEFAULT:
80              this.compressionLevel = compressionLevel;
81              break;
82          default:
83              throw new IllegalArgumentException(
84                      "invalid compression level specified");
85          }
86  
87          // create a new instance of ZStream. This will be done only once.
88          zStream = new ZStream();
89  
90          switch (mode) {
91          case MODE_DEFLATER:
92              zStream.deflateInit(this.compressionLevel);
93              break;
94          case MODE_INFLATER:
95              zStream.inflateInit();
96              break;
97          default:
98              throw new IllegalArgumentException("invalid mode specified");
99          }
100         this.mode = mode;
101     }
102 
103     /**
104      * Uncompress the given buffer, returning it in a new buffer.
105      * 
106      * @param inBuffer the {@link IoBuffer} to be decompressed. The contents
107      * of the buffer are transferred into a local byte array and the buffer is
108      * flipped and returned intact.
109      * @return the decompressed data
110      * @throws IOException if the decompression of the data failed for some reason.
111      * @throws IllegalArgumentException if the mode is not <code>MODE_DEFLATER</code>
112      */
113     public IoBuffer inflate(IoBuffer inBuffer) throws IOException {
114         if (mode == MODE_DEFLATER) {
115             throw new IllegalStateException("not initialized as INFLATER");
116         }
117 
118         byte[] inBytes = new byte[inBuffer.remaining()];
119         inBuffer.get(inBytes).flip();
120 
121         // We could probably do this better, if we're willing to return multiple buffers
122         // (e.g. with a callback function)
123         byte[] outBytes = new byte[inBytes.length * 2];
124         IoBuffer outBuffer = IoBuffer.allocate(outBytes.length);
125         outBuffer.setAutoExpand(true);
126 
127         zStream.next_in = inBytes;
128         zStream.next_in_index = 0;
129         zStream.avail_in = inBytes.length;
130         zStream.next_out = outBytes;
131         zStream.next_out_index = 0;
132         zStream.avail_out = outBytes.length;
133         int retval = 0;
134 
135         do {
136             retval = zStream.inflate(JZlib.Z_SYNC_FLUSH);
137             switch (retval) {
138             case JZlib.Z_OK:
139                 // completed decompression, lets copy data and get out
140             case JZlib.Z_BUF_ERROR:
141                 // need more space for output. store current output and get more
142                 outBuffer.put(outBytes, 0, zStream.next_out_index);
143                 zStream.next_out_index = 0;
144                 zStream.avail_out = outBytes.length;
145                 break;
146             default:
147                 // unknown error
148                 outBuffer = null;
149                 if (zStream.msg == null) {
150                     throw new IOException("Unknown error. Error code : "
151                             + retval);
152                 } else {
153                     throw new IOException("Unknown error. Error code : "
154                             + retval + " and message : " + zStream.msg);
155                 }
156             }
157         } while (zStream.avail_in > 0);
158 
159         return outBuffer.flip();
160     }
161 
162     /**
163      * Compress the input. The result will be put in a new buffer.
164      *  
165      * @param inBuffer the buffer to be compressed. The contents are transferred
166      * into a local byte array and the buffer is flipped and returned intact.
167      * @return the buffer with the compressed data
168      * @throws IOException if the compression of teh buffer failed for some reason
169      * @throws IllegalStateException if the mode is not <code>MODE_DEFLATER</code>
170      */
171     public IoBuffer deflate(IoBuffer inBuffer) throws IOException {
172         if (mode == MODE_INFLATER) {
173             throw new IllegalStateException("not initialized as DEFLATER");
174         }
175 
176         byte[] inBytes = new byte[inBuffer.remaining()];
177         inBuffer.get(inBytes).flip();
178 
179         // according to spec, destination buffer should be 0.1% larger
180         // than source length plus 12 bytes. We add a single byte to safeguard
181         // against rounds that round down to the smaller value
182         int outLen = (int) Math.round(inBytes.length * 1.001) + 1 + 12;
183         byte[] outBytes = new byte[outLen];
184 
185         zStream.next_in = inBytes;
186         zStream.next_in_index = 0;
187         zStream.avail_in = inBytes.length;
188         zStream.next_out = outBytes;
189         zStream.next_out_index = 0;
190         zStream.avail_out = outBytes.length;
191 
192         int retval = zStream.deflate(JZlib.Z_SYNC_FLUSH);
193         if (retval != JZlib.Z_OK) {
194             outBytes = null;
195             inBytes = null;
196             throw new IOException("Compression failed with return value : "
197                     + retval);
198         }
199 
200         IoBuffer outBuf = IoBuffer
201                 .wrap(outBytes, 0, zStream.next_out_index);
202 
203         return outBuf;
204     }
205 
206     /**
207      * Cleans up the resources used by the compression library.
208      */
209     public void cleanUp() {
210         if (zStream != null) {
211             zStream.free();
212         }
213     }
214 }