sstrecord.java

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/* ====================================================================
   Copyright 2002-2004   Apache Software Foundation

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
==================================================================== */
        

package org.apache.poi.hssf.record;

import org.apache.poi.util.BinaryTree;
import org.apache.poi.util.LittleEndian;
import org.apache.poi.util.LittleEndianConsts;

import java.util.Iterator;
import java.util.List;

/**
 * Title:        Static String Table Record
 * <P>
 * Description:  This holds all the strings for LabelSSTRecords.
 * <P>
 * REFERENCE:    PG 389 Microsoft Excel 97 Developer's Kit (ISBN:
 *               1-57231-498-2)
 * <P>
 * @author Andrew C. Oliver (acoliver at apache dot org)
 * @author Marc Johnson (mjohnson at apache dot org)
 * @author Glen Stampoultzis (glens at apache.org)
 *
 * @see org.apache.poi.hssf.record.LabelSSTRecord
 * @see org.apache.poi.hssf.record.ContinueRecord
 */

public class SSTRecord
        extends Record
{

    /** how big can an SST record be? As big as any record can be: 8228 bytes */
    static final int MAX_RECORD_SIZE = 8228;

    /** standard record overhead: two shorts (record id plus data space size)*/
    static final int STD_RECORD_OVERHEAD =
            2 * LittleEndianConsts.SHORT_SIZE;

    /** SST overhead: the standard record overhead, plus the number of strings and the number of unique strings -- two ints */
    static final int SST_RECORD_OVERHEAD =
            ( STD_RECORD_OVERHEAD + ( 2 * LittleEndianConsts.INT_SIZE ) );

    /** how much data can we stuff into an SST record? That would be _max minus the standard SST record overhead */
    static final int MAX_DATA_SPACE = MAX_RECORD_SIZE - SST_RECORD_OVERHEAD;

    /** overhead for each string includes the string's character count (a short) and the flag describing its characteristics (a byte) */
    static final int STRING_MINIMAL_OVERHEAD = LittleEndianConsts.SHORT_SIZE + LittleEndianConsts.BYTE_SIZE;

    public static final short sid = 0xfc;

    /** union of strings in the SST and EXTSST */
    private int field_1_num_strings;

    /** according to docs ONLY SST */
    private int field_2_num_unique_strings;
    private BinaryTree field_3_strings;

    /** Record lengths for initial SST record and all continue records */
    private List _record_lengths = null;
    private SSTDeserializer deserializer;

    /** Offsets from the beginning of the SST record (even across continuations) */
    int[] bucketAbsoluteOffsets;
    /** Offsets relative the start of the current SST or continue record */
    int[] bucketRelativeOffsets;

    /**
     * default constructor
     */
    public SSTRecord()
    {
        field_1_num_strings = 0;
        field_2_num_unique_strings = 0;
        field_3_strings = new BinaryTree();
        deserializer = new SSTDeserializer(field_3_strings);
    }

    /**
     * Constructs an SST record and sets its fields appropriately.
     *
     * @param id must be 0xfc or an exception will be throw upon
     *           validation
     * @param size the size of the data area of the record
     * @param data of the record (should not contain sid/len)
     */

    public SSTRecord( final short id, final short size, final byte[] data )
    {
        super( id, size, data );
    }

    /**
     * Constructs an SST record and sets its fields appropriately.
     *
     * @param id must be 0xfc or an exception will be throw upon
     *           validation
     * @param size the size of the data area of the record
     * @param data of the record (should not contain sid/len)
     * @param offset of the record
     */

    public SSTRecord( final short id, final short size, final byte[] data,
                      int offset )
    {
        super( id, size, data, offset );
    }

    /**
     * Add a string. Determines whether 8-bit encoding can be used, or
     * whether 16-bit encoding must be used.
     * <p>
     * THIS IS THE PREFERRED METHOD OF ADDING A STRING. IF YOU USE THE
     * OTHER ,code>addString</code> METHOD AND FORCE 8-BIT ENCODING ON
     * A STRING THAT SHOULD USE 16-BIT ENCODING, YOU WILL CORRUPT THE
     * STRING; IF YOU USE THAT METHOD AND FORCE 16-BIT ENCODING, YOU
     * ARE WASTING SPACE WHEN THE WORKBOOK IS WRITTEN OUT.
     *
     * @param string string to be added
     *
     * @return the index of that string in the table
     */

    public int addString( final String string )
    {
        int rval;

        if ( string == null )
        {
            rval = addString( "", false );
        }
        else
        {

            // scan for characters greater than 255 ... if any are
            // present, we have to use 16-bit encoding. Otherwise, we
            // can use 8-bit encoding
            boolean useUTF16 = false;
            int strlen = string.length();

            for ( int j = 0; j < strlen; j++ )
            {
                if ( string.charAt( j ) > 255 )
                {
                    useUTF16 = true;
                    break;
                }
            }
            rval = addString( string, useUTF16 );
        }
        return rval;
    }

    /**
     * Add a string and assert the encoding (8-bit or 16-bit) to be
     * used.
     * <P>
     * USE THIS METHOD AT YOUR OWN RISK. IF YOU FORCE 8-BIT ENCODING,
     * YOU MAY CORRUPT YOUR STRING. IF YOU FORCE 16-BIT ENCODING AND
     * IT ISN'T NECESSARY, YOU WILL WASTE SPACE WHEN THIS RECORD IS
     * WRITTEN OUT.
     *
     * @param string string to be added
     * @param useUTF16 if true, forces 16-bit encoding. If false,
     *                 forces 8-bit encoding
     *
     * @return the index of that string in the table
     */

    public int addString( final String string, final boolean useUTF16 )
    {
        field_1_num_strings++;
        String str = ( string == null ) ? ""
                : string;
        int rval;
        UnicodeString ucs = new UnicodeString();

        ucs.setString( str );
        ucs.setCharCount( (short) str.length() );
        ucs.setOptionFlags( (byte) ( useUTF16 ? 1
                : 0 ) );
        Integer integer = (Integer) field_3_strings.getKeyForValue( ucs );

        if ( integer != null )
        {
            rval = integer.intValue();
        }
        else
        {

            // This is a new string -- we didn't see it among the
            // strings we've already collected
            rval = field_3_strings.size();
            field_2_num_unique_strings++;
            integer = new Integer( rval );
            SSTDeserializer.addToStringTable( field_3_strings, integer, ucs );
//            field_3_strings.put( integer, ucs );
        }
        return rval;
    }

    /**
     * @return number of strings
     */

    public int getNumStrings()
    {
        return field_1_num_strings;
    }

    /**
     * @return number of unique strings
     */

    public int getNumUniqueStrings()
    {
        return field_2_num_unique_strings;
    }

    /**
     * USE THIS METHOD AT YOUR OWN PERIL: THE <code>addString</code>
     * METHODS MANIPULATE THE NUMBER OF STRINGS AS A SIDE EFFECT; YOUR
     * ATTEMPTS AT MANIPULATING THE STRING COUNT IS LIKELY TO BE VERY
     * WRONG AND WILL RESULT IN BAD BEHAVIOR WHEN THIS RECORD IS
     * WRITTEN OUT AND ANOTHER PROCESS ATTEMPTS TO READ THE RECORD
     *
     * @param count  number of strings
     *
     */

    public void setNumStrings( final int count )
    {
        field_1_num_strings = count;
    }

    /**
     * USE THIS METHOD AT YOUR OWN PERIL: THE <code>addString</code>
     * METHODS MANIPULATE THE NUMBER OF UNIQUE STRINGS AS A SIDE
     * EFFECT; YOUR ATTEMPTS AT MANIPULATING THE UNIQUE STRING COUNT
     * IS LIKELY TO BE VERY WRONG AND WILL RESULT IN BAD BEHAVIOR WHEN
     * THIS RECORD IS WRITTEN OUT AND ANOTHER PROCESS ATTEMPTS TO READ
     * THE RECORD
     *
     * @param count  number of strings
     */

    public void setNumUniqueStrings( final int count )
    {
        field_2_num_unique_strings = count;
    }

    /**
     * Get a particular string by its index
     *
     * @param id index into the array of strings
     *
     * @return the desired string
     */

    public String getString( final int id )
    {
        return ( (UnicodeString) field_3_strings.get( new Integer( id ) ) ).getString();
    }