Add CRCChecker

This class checks given blocks of image files against a given crc file

3 files changed, 197 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;
+	}
+}
diff --git a/src/main/java/org/openslx/imagemaster/crcchecker/CRCFile.java b/src/main/java/org/openslx/imagemaster/crcchecker/CRCFile.java
new file mode 100644
index 0000000..3a75b37
--- /dev/null
+++ b/src/main/java/org/openslx/imagemaster/crcchecker/CRCFile.java
@@ -0,0 +1,72 @@
+package org.openslx.imagemaster.crcchecker;
+
+import java.io.DataInputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.zip.CRC32;
+
+/**
+ * Represents a crcfile
+ * @author nils
+ *
+ */
+public class CRCFile
+{
+	private File file;
+	private List<Integer> crcSums = null;
+	
+	CRCFile(String filename) {
+		this.file = new File( filename );
+	}
+	
+	/**
+	 * 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 {
+		FileInputStream fis = new FileInputStream( file );
+		DataInputStream dis = new DataInputStream( fis );
+		
+		int crcSum = dis.readInt();
+		
+		CRC32 crcCalc = new CRC32();
+		
+		byte[] bytes = new byte[(int) file.length() - Integer.SIZE/8];	// byte array with length of the file minus the first crc sum (=4byte)
+		fis.read( bytes );
+		crcCalc.update( bytes );
+		
+		dis.close();
+		
+		if (crcSum == Integer.reverseBytes( (int) crcCalc.getValue() ) ) return true;
+		else return false;
+	}
+	
+	/**
+	 * Get a specified crcSum for a block number
+	 * @param blockNumber
+	 * @return The crcSum or 0 if the block number is invalid
+	 * @throws IOException 
+	 */
+	public int getCRCSum(int blockNumber) throws IOException {
+		if (crcSums == null) {
+			// the crcSum were not read yet
+			DataInputStream dis = new DataInputStream( new FileInputStream( file ) );
+			crcSums = new ArrayList<>();
+			for (int i = 0; i < file.length()/4; i++) {
+				int s = dis.readInt();
+				if (i > 0) crcSums.add( s );	// skip the first crcSum because it's the sum over the crcFile
+			}
+			dis.close();
+		}
+		
+		if (blockNumber < 0) return 0;
+		if (blockNumber > crcSums.size() - 1) return 0; 
+		
+		return crcSums.get( blockNumber );
+	}		
+}
diff --git a/src/main/java/org/openslx/imagemaster/crcchecker/ImageFile.java b/src/main/java/org/openslx/imagemaster/crcchecker/ImageFile.java
new file mode 100644
index 0000000..a6ff8f0
--- /dev/null
+++ b/src/main/java/org/openslx/imagemaster/crcchecker/ImageFile.java
@@ -0,0 +1,48 @@
+package org.openslx.imagemaster.crcchecker;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+
+/**
+ * Representing an image file.
+ * Is able to return certain blocks of this file.
+ * @author nils
+ *
+ */
+public class ImageFile
+{
+	private File file;
+	private int blockSize;
+	
+	public ImageFile(String filename, int blockSize) {
+		this.file = new File( filename );
+		this.blockSize = blockSize;
+	}
+	
+	/**
+	 * Get a certain block
+	 * @param block The number of the block you want to get
+	 * @return The specified block
+	 * @throws IOException When file was not found or could not be read
+	 */
+	public byte[] getBlock(int block) throws IOException {
+		if (block < 0) return null;
+		if (block > file.length()/blockSize) return null;
+		
+		FileInputStream fis = new FileInputStream( file );
+		
+		fis.skip( block * (long) blockSize );
+		
+		byte[] result = new byte[ ( blockSize > fis.available() )? fis.available() : blockSize ];	// only read availible bytes
+		
+		fis.read(result);
+		fis.close();
+		
+		return result;
+	}
+	
+	public long length() {
+		return file.length();
+	}
+}