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/* 
 * Copyright (C) 2002-2016 XimpleWare, [email protected]
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */
/*VTD-XML is protected by US patent 7133857, 7260652, an 7761459*/
package com.ximpleware.extended;
import java.io.*;
import java.nio.*;
import java.nio.channels.*;
/**
 * 
 * XMLMemMappedBuffer maps an XML document into memory using memory map.
 * It avoids the complete loading of the document in memory thus making it
 * possible to process very large files. But the trade off is potentially 
 * lower performance due to disk IO.
 */

public class XMLMemMappedBuffer implements IByteBuffer {
    MappedByteBuffer input[];
    FileChannel fc;
    RandomAccessFile raf;
    String fn;
    long length;
    public XMLMemMappedBuffer(){
        
    }
    
    public long length(){
        return length;
    }
    
    public byte byteAt(long index){
        return input[(int)(index>>30)].get((int)(index & 0x3fffffff));
    }
    
    public void readFile(String fileName) throws java.io.IOException, ParseExceptionHuge {
        File f = new File(fileName);
        fn = fileName;
        long l = f.length();
        length = l;
        if (l>= (1L<< 38)){
            throw new ParseExceptionHuge("document too big > 256 Gbyte");
        }
        raf = new RandomAccessFile(fileName, "r");
        fc  = raf.getChannel();
        int pageNumber = (int)(l>>30)+(((l & 0x3fffffffL)==0)?0:1);
                
        input = new MappedByteBuffer[pageNumber];
        long l2 =0;
        for (int i=0;i