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package org.openslx.imagemaster.crcchecker;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.CRC32;
/**
* Represents a crcfile
*
* @author nils
*
*/
public class CRCFile
{
private File file;
public final List<Integer> crcSums = null;
/**
* Loads a crcFile from file
*
* @param filename
*/
CRCFile( String filename )
{
this.file = new File( filename );
}
/**
* Creates a new crc file with the given sums.
* The first crc sum in the list needs to be the sum over the other sums.
*
* @param listOfCrcSums The list of the crc sums that are going into the crc file
* @param filename Where to save the created crc file
* @throws IOException If it's not possible to write the file
*/
public CRCFile( List<Integer> listOfCrcSums, String filename ) throws IOException
{
this.file = new File( filename );
FileOutputStream fos = new FileOutputStream( file );
DataOutputStream dos = new DataOutputStream( fos );
for ( Integer sum : listOfCrcSums ) {
dos.writeInt( Integer.reverseBytes( sum.intValue() ) ); // save byte-reversed integers to match right order in crc file
}
dos.close();
this.crcSums = listOfCrcSums;
}
/**
* Checks if this crc file is valid.
* (If the crc over the file is equal to the first crc sum.)
*
* @return Whether the crc file is valid
* @throws IOException If the file could not be read or could not be found
*/
public boolean isValid() throws IOException
{
FileInputStream fis = new FileInputStream( file );
DataInputStream dis = new DataInputStream( fis );
int crcSum = dis.readInt();
CRC32 crcCalc = new CRC32();
byte[] bytes = new byte[ (int)file.length() - Integer.SIZE / 8 ]; // byte array with length of the file minus the first crc sum (=4byte)
fis.read( bytes );
crcCalc.update( bytes );
dis.close();
if ( crcSum == Integer.reverseBytes( (int)crcCalc.getValue() ) )
return true;
else
return false;
}
/**
* Get a specified crcSum for a block number
*
* @param blockNumber
* @return The crcSum or 0 if the block number is invalid
* @throws IOException
*/
public int getCRCSum( int blockNumber ) throws IOException
{
if ( crcSums == null ) {
// the crcSums were not read yet
DataInputStream dis = new DataInputStream( new FileInputStream( file ) );
crcSums = new ArrayList<>();
for ( int i = 0; i < file.length() / 4; i++ ) {
int s = dis.readInt();
if ( i > 0 )
crcSums.add( s ); // skip the first crcSum because it's the sum over the crcFile
}
dis.close();
}
if ( blockNumber < 0 )
return 0;
if ( blockNumber > crcSums.size() - 1 )
return 0;
return crcSums.get( blockNumber );
}
}
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