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package org.openslx.imagemaster.crcchecker;
import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
import java.util.zip.CRC32;
import org.apache.log4j.Logger;
import org.openslx.imagemaster.Globals;
// TODO: Move to master-sync-shared, sattelite daemon might want to check images too
public class CRCChecker
{
private static Logger log = Logger.getLogger( CRCChecker.class );
/**
* Checks the CRC sum of given blocks of a given imageFile against a given crcFile.
* @param imageFile The imageFile to check
* @param crcFile The crcFile to check against
* @param blocks The blocks to check
* @return List of blocks where the crc matches, or null if the crc file is corrupted
*/
public static List<Integer> checkCRC(String imageFile, String crcFile, List<Integer> blocks) throws IOException
{
List<Integer> result = new LinkedList<>();
ImageFile image = new ImageFile( imageFile, Globals.blockSize );
CRCFile crc = new CRCFile( crcFile );
log.debug( "Checking image file: '" + imageFile + "' with crc file: '" + crcFile + "'");
try {
if (!crc.isValid()) return null;
// TODO: also return null if the crc file contains the wrong number of checksums (only makes sense if the upload is complete)
} catch (IOException e) {
throw new IOException( "Could not read CRC file", e );
}
// file is smaller than one block - no need to check crc yet
// TODO: Needs more logic, if the image is complete and < 16MB, we still need to check the block.
// The caller should make sure to only check crc of blocks that are finished downloading
if (image.length() < Globals.blockSize) {
return result;
}
// check all blocks
for (Integer blockN : blocks) {
byte[] block;
try {
// TODO: For performance improvements maybe prealloc the array outside the loop with a size of Globals.BLOCK_SIZE
// and then make getBlock(blockN, block) return the actual size of the block (Should always be BLOCK_SIZE except
// for the last block), so you never need to create fresh byte arrays inside the loop
block = image.getBlock( blockN );
} catch ( IOException e ) {
throw new IOException( "Could not read image file", e );
}
if (block == null) continue; // some error occured (for example: someone tried to check a block that is not in the file)
// check this block with CRC32
// add this block to result, if check was ok with CRC file
CRC32 crcCalc = new CRC32();
crcCalc.update( block );
int crcSum = Integer.reverseBytes( (int) crcCalc.getValue() );
int crcSumFromFile;
try {
crcSumFromFile = crc.getCRCSum( blockN );
} catch ( IOException e ) {
throw new IOException( "Could not read CRC file", e );
}
if (crcSum == crcSumFromFile) result.add( blockN );
else log.debug(blockN + " was invalid");
}
return result;
}
}
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