1 files changed, 76 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..9ca3d55
--- /dev/null
+++ b/src/main/java/org/openslx/imagemaster/crcchecker/CRCChecker.java
@@ -0,0 +1,76 @@
+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;
+
+// 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 );
+	private static final int blockSize = 16 * 1024 * 1024;
+
+	/**
+	 * Checks the CRC sum of given blocks of a given imageFile against a given crcFile.
+	 * The caller needs to make sure that block that are going to be checked are complete!
+	 * 
+	 * @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, 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 );
+		}
+
+		// check all blocks
+		byte[] block = new byte[blockSize];
+		for ( Integer blockN : blocks ) {
+			try {
+				image.getBlock( blockN, block );
+			} 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;
+	}
+}