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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.util.Arrays;
import java.util.List;
import java.util.zip.CRC32;
/**
* Represents a crc file
*/
public class CrcFile
{
private final int masterCrc;
private final int[] crcSums;
private Boolean valid = null;
/**
* Loads a crcFile from file
*
* @param filename
* @throws IOException
*/
public CrcFile( String filename ) throws IOException
{
File file = new File( filename );
DataInputStream dis = null;
try {
dis = new DataInputStream( new FileInputStream( file ) );
int numSums = (int) ( file.length() / 4 ) - 1;
if ( numSums < 0 )
throw new IOException( "Invalid crc file: " + filename );
masterCrc = dis.readInt();
int[] sums = new int[ numSums ];
for ( int i = 0; i < numSums; i++ ) {
sums[i] = dis.readInt();
}
crcSums = sums;
} finally {
if ( dis != null )
try {
dis.close();
} catch ( Throwable t ) {
}
}
}
/**
* Creates a crc file which is not on the drive.
*
* @param crcSums
*/
public CrcFile( int[] crcSumsWithLeadingMasterCrc )
{
this.masterCrc = crcSumsWithLeadingMasterCrc[0];
this.crcSums = Arrays.copyOfRange( crcSumsWithLeadingMasterCrc, 1, crcSumsWithLeadingMasterCrc.length );
}
public CrcFile( List<Integer> crcSumsWithLeadingMasterCrc )
{
this.masterCrc = crcSumsWithLeadingMasterCrc.get( 0 );
this.crcSums = new int[ crcSumsWithLeadingMasterCrc.size() - 1 ];
for ( int i = 0; i < crcSums.length; i++ )
crcSums[i] = crcSumsWithLeadingMasterCrc.get( i + 1 );
}
/**
* 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.
* Deletes existing files with the same name.
*
* @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 void writeCrcFile( String filename ) throws IOException
{
File file = new File( filename );
if ( file.exists() )
file.delete();
FileOutputStream fos = new FileOutputStream( file );
DataOutputStream dos = null;
try {
dos = new DataOutputStream( fos );
dos.writeInt( Integer.reverseBytes( masterCrc ) );
for ( int sum : crcSums ) {
dos.writeInt( Integer.reverseBytes( sum ) );
}
} finally {
if ( dos != null )
dos.close();
}
}
/**
* 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
*/
public boolean isValid()
{
if ( valid == null ) {
if ( crcSums == null || crcSums.length < 1 )
return false;
int masterSum = crcSums[0];
CRC32 crcCalc = new CRC32();
byte[] buffer = new byte[ 4 ];
for ( int i = 1; i < crcSums.length; i++ ) {
crcCalc.update( intToByteArrayLittleEndian( crcSums[i], buffer ) ); // update the crc calculator with the next 4 bytes of the integer
}
valid = ( masterSum == Integer.reverseBytes( (int)crcCalc.getValue() ) );
}
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 )
{
if ( crcSums == null || blockNumber < 0 || blockNumber >= crcSums.length )
return 0;
return crcSums[blockNumber];
}
public int getMasterSum()
{
return masterCrc;
}
private static final byte[] intToByteArrayLittleEndian( int value, byte[] buffer )
{
buffer[3] = (byte) ( value >>> 24 );
buffer[2] = (byte) ( value >>> 16 );
buffer[1] = (byte) ( value >>> 8 );
buffer[0] = (byte)value;
return buffer;
}
}
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