CompressionOutputStream


1   /*
2    * $Id: CompressionOutputStream.java 5462 2005-08-05 18:35:48Z jonesde $
3    *
4    * Copyright (c) 1998, 1999 Sun Microsystems, Inc. All Rights Reserved.
5    *
6    * Sun grants you ("Licensee") a non-exclusive, royalty free, license to use,
7    * modify and redistribute this software in source and binary code form,
8    * provided that i) this copyright notice and license appear on all copies of
9    * the software; and ii) Licensee does not utilize the software in a manner
10   * which is disparaging to Sun.
11   *
12   * This software is provided "AS IS," without a warranty of any kind. ALL
13   * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY
14   * IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR
15   * NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE
16   * LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
17   * OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS
18   * LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT,
19   * INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER
20   * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF
21   * OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
22   * POSSIBILITY OF SUCH DAMAGES.
23   *
24   * This software is not designed or intended for use in on-line control of
25   * aircraft, air traffic, aircraft navigation or aircraft communications; or in
26   * the design, construction, operation or maintenance of any nuclear
27   * facility. Licensee represents and warrants that it will not use or
28   * redistribute the Software for such purposes.
29   */
30  
31  package org.ofbiz.service.rmi.socket.zip;
32  
33  import java.io.FilterOutputStream  ;
34  import java.io.IOException  ;
35  import java.io.OutputStream  ;
36  
37  public class CompressionOutputStream extends FilterOutputStream   implements CompressionConstants {
38  
39      /*
40       * Constructor calls constructor of superclass.
41       */
42      public CompressionOutputStream(OutputStream   out) {
43          super(out);
44      }
45  
46      /*
47       * Buffer of 6-bit codes to pack into next 32-bit word
48       * Five 6-bit codes fit into 4 words.
49       */
50      int buf[] = new int[5];
51  
52      /*
53       * Index of valid codes waiting in buf.
54       */
55      int bufPos = 0;
56  
57  
58      /*
59       * This method writes one byte to the socket stream.
60       */
61      public void write(int b) throws IOException   {
62          // force argument to one byte
63          b &= 0xFF;
64  
65          // Look up pos in codeTable to get its encoding.
66          int pos = codeTable.indexOf((char) b);
67  
68          if (pos != -1) {
69              // If pos is in the codeTable, write BASE + pos into buf.
70              // By adding BASE to pos, we know that the characters in
71              // the codeTable will always have a code between 2 and 63
72              // inclusive. This allows us to use RAW (RAW is equal to
73              // 1) to signify that the next two groups of 6-bits are
74              // necessary for decompression of the next character.
75  
76              writeCode(BASE + pos);
77          } else {
78              // Otherwise, write RAW into buf to signify that the
79              // Character is being sent in 12 bits.
80              writeCode(RAW);
81  
82              // Write the last 4 bits of b into the buf.
83              writeCode(b >> 4);
84  
85              // Truncate b to contain data in only the first 4 bits,
86              // and write the first 4 bits of b into buf.
87              writeCode(b & 0xF);
88          }
89      }
90  
91      /*
92       * This method writes up to len bytes to the socket stream.
93       */
94      public void write(byte b[], int off, int len) throws IOException   {
95          /*
96           * This implementation is quite inefficient because it has to
97           * call the other write method for every byte in the array.  It
98           * could be optimized for performance by doing all the processing
99           * in this method.
100          */
101         for (int i = 0; i < len; i++)
102             write(b[off + i]);
103     }
104 
105 
106     /*
107      * Clears buffer of all data (zeroes it out).
108      */
109     public void flush() throws IOException   {
110         while (bufPos > 0)
111             writeCode(NOP);
112     }
113 
114     /*
115      * This method actually puts the data into the output stream after
116      * packing the data from all 5 bytes in buf into one word.
117      * Remember, each byte has, at most, 6 significant bits.
118      */
119     private void writeCode(int c) throws IOException   {
120         buf[bufPos++] = c;
121         if (bufPos == 5) {      // write next word when we have 5 codes
122             int pack = (buf[0] << 24) | (buf[1] << 18) | (buf[2] << 12) |
123                     (buf[3] << 6) | buf[4];
124             out.write((pack >>> 24) & 0xFF);
125             out.write((pack >>> 16) & 0xFF);
126             out.write((pack >>> 8) & 0xFF);
127             out.write((pack >>> 0) & 0xFF);
128             bufPos = 0;
129         }
130     }
131 }
132
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