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Java > Open Source Codes > jxl > write > biff > ExtendedSSTRecord


1 /*********************************************************************
2 *
3 * Copyright (C) 2002 Andrew Khan
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2.1 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 ***************************************************************************/
19
20 package jxl.write.biff;
21
22 import jxl.biff.Type;
23 import jxl.biff.IntegerHelper;
24 import jxl.biff.WritableRecordData;
25
26 /**
27  * Indicates an extension to the Shared String Table. Currently this
28  * contains blank records
29  *
30  * Thanks to Guenther for contributing a proper implementation of the EXTSST
31  * record, replacing my previous dummy version
32  */
33 class ExtendedSSTRecord extends WritableRecordData
34 {
35   private static final int infoRecordSize = 8;
36   private int numberOfStrings;
37   private int[] absoluteStreamPositions;
38   private int[] relativeStreamPositions;
39   private int currentStringIndex = 0;
40   
41   /**
42    * Constructor
43    *
44    * @param numstrings the number of strings per bucket
45    * @param streampos the absolute stream position of the beginning of
46    * the SST record
47    */
48   public ExtendedSSTRecord(int newNumberOfStrings)
49   {
50     super(Type.EXTSST);
51     numberOfStrings = newNumberOfStrings;
52     int numberOfBuckets = getNumberOfBuckets();
53     absoluteStreamPositions = new int[numberOfBuckets];
54     relativeStreamPositions = new int[numberOfBuckets];
55     currentStringIndex = 0;
56   }
57
58   public int getNumberOfBuckets()
59   {
60     int numberOfStringsPerBucket = getNumberOfStringsPerBucket();
61     return numberOfStringsPerBucket != 0 ?
62       (numberOfStrings + numberOfStringsPerBucket - 1) /
63       numberOfStringsPerBucket : 0;
64   }
65
66   public int getNumberOfStringsPerBucket()
67   {
68     // XXX
69 // should come up with a more clever calculation
70 // bucket limit should not be bigger than 1024, otherwise we end
71 // up with too many buckets and would have to write continue records
72 // for the EXTSST record which we want to avoid for now.
73 final int bucketLimit = 128;
74     return (numberOfStrings + bucketLimit - 1) / bucketLimit;
75   }
76   
77   public void addString(int absoluteStreamPosition,
78                         int relativeStreamPosition)
79   {
80     absoluteStreamPositions[currentStringIndex] =
81       absoluteStreamPosition + relativeStreamPosition;
82     relativeStreamPositions[currentStringIndex] = relativeStreamPosition;
83     currentStringIndex++;
84   }
85
86   /**
87    * Gets the binary data to be written out
88    *
89    * @return the binary data
90    */
91   public byte[] getData()
92   {
93     int numberOfBuckets = getNumberOfBuckets();
94     byte[] data = new byte[2 + (8 * numberOfBuckets)];
95     // number of strings per bucket
96 IntegerHelper.getTwoBytes(getNumberOfStringsPerBucket(), data, 0);
97     
98     for (int i = 0; i < numberOfBuckets; i++)
99     {
100       // absolute stream position
101 IntegerHelper.getFourBytes(absoluteStreamPositions[i],
102                                  data,
103                                  2 + (i * infoRecordSize));
104       // relative offset
105 IntegerHelper.getTwoBytes(relativeStreamPositions[i],
106                                 data,
107                                 6 + (i * infoRecordSize));
108       // reserved
109 // IntegerHelper.getTwoBytes(0x0, data, 8 + (i * infoRecordSize));
110 }
111
112     return data;
113   }
114 }
115
116
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