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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.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.CRC32;
/**
* Represents a crc file
*/
public class CRCFile
{
private File file = null;
private List<Integer> crcSums = null;
private Boolean valid = null;
/**
* Loads a crcFile from file
*
* @param filename
*/
public CRCFile( String filename )
{
this.file = new File( filename );
}
/**
* Creates a crc file which is not on the drive.
*
* @param crcSums
*/
public CRCFile( List<Integer> crcSums )
{
this.crcSums = crcSums;
}
/**
* 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 static CRCFile writeCrcFile( List<Integer> listOfCrcSums, String filename ) throws IOException
{
File file = new File( filename );
FileOutputStream fos = new FileOutputStream( file );
DataOutputStream dos = new DataOutputStream( fos );
for ( Integer sum : listOfCrcSums ) {
dos.writeInt( sum.intValue() );
}
dos.close();
return new CRCFile( filename );
}
/**
* Checks if given sums are valid.
*
* @param listOfCrcSums
* @return
*/
public static boolean sumsAreValid( List<Integer> listOfCrcSums )
{
if ( listOfCrcSums == null || listOfCrcSums.isEmpty() )
return false;
int masterSum = listOfCrcSums.get( 0 ); // don't use the first sum for the calculation because it is the sum over the other sums
int size = listOfCrcSums.size();
CRC32 crcCalc = new CRC32();
for ( int i = 1; i < size; i++ ) {
crcCalc.update( ByteBuffer.allocate( 4 ).putInt( listOfCrcSums.get( i ) ).array() ); // update the crc calculator with the next 4 bytes of the integer
}
return ( masterSum == Integer.reverseBytes( (int)crcCalc.getValue() ) );
}
/**
* 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
{
if ( valid == null ) {
if ( file == null ) {
valid = sumsAreValid( this.crcSums );
} else {
if ( crcSums == null )
loadSums();
valid = sumsAreValid( this.crcSums );
}
}
return valid;
}
/**
* Get a specified crcSum for a block number
*
* @param blockNumber
* @return The crcSum or 0 if the block number is invalid
* @throws IOException If the crcSums could not be loaded from file
*/
public int getCRCSum( int blockNumber ) throws IOException
{
if ( crcSums == null )
loadSums();
if ( blockNumber < 0 )
return 0;
if ( blockNumber > crcSums.size() - 2 )
return 0;
return crcSums.get( blockNumber + 1 );
}
/**
* Returns the loaded crcSums.
*
* @return The loaded crcSums
* @throws IOException If the crcSums could not be loaded from file
*/
public List<Integer> getCrcSums() throws IOException
{
if ( crcSums == null )
loadSums();
return this.crcSums;
}
private void loadSums() throws IOException
{
if ( crcSums != null )
return;
// 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++ ) {
crcSums.add( dis.readInt() );
}
dis.close();
}
public int getMasterSum() throws IOException
{
if ( crcSums == null )
loadSums();
return this.crcSums.get( 0 );
}
}
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