1 files changed, 77 insertions, 0 deletions
diff --git a/src/main/java/org/openslx/imagemaster/crcchecker/CRCChecker.java b/src/main/java/org/openslx/imagemaster/crcchecker/CRCChecker.java
new file mode 100644
index 0000000..04f6a22
--- /dev/null
+++ b/src/main/java/org/openslx/imagemaster/crcchecker/CRCChecker.java
@@ -0,0 +1,77 @@
+package org.openslx.imagemaster.crcchecker;
+
+import java.io.DataInputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.zip.CRC32;
+
+import org.apache.log4j.Logger;
+
+
+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 The blocks where the crc was right
+	 */
+	public static List<Integer> checkCRC(String imageFile, String crcFile, List<Integer> blocks) throws IOException
+	{
+		List<Integer> result = new LinkedList<>();
+		
+		final int blockSize = 16 * 1024 * 1024;
+		
+		ImageFile image = new ImageFile( imageFile, blockSize );
+		CRCFile crc = new CRCFile( crcFile );
+		
+		log.debug( "Checking image file: '" + imageFile + "' with crc file: '" + crcFile + "'");
+		try {
+			if (!crc.isValid()) return result;	// TODO: this needs to be handled in another way
+		} catch (IOException e) {
+			throw new IOException( "Could not read CRC file", e );
+		}
+		
+		// file is smaller than one block - no need to check crc yet
+		if (image.length() < blockSize) {
+			return result;
+		}
+		// check all blocks
+		for (Integer blockN : blocks) {
+			byte[] block;
+			try {
+				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() );
+			log.debug( "Got crc for block '" + blockN + "': '" + crcSum + "'" );
+			int crcSumFromFile;
+			try {
+				crcSumFromFile = crc.getCRCSum( blockN );
+			} catch ( IOException e ) {
+				throw new IOException( "Could not read CRC file", e );
+			}
+			log.debug( "And read crc from file: '" + crcSumFromFile + "'" );
+			
+			if (crcSum ==  crcSumFromFile) result.add( blockN );
+		}
+		
+		return result;
+	}
+}