Move crc checler from masterserver to master-sync-shared

1 files changed, 72 insertions, 0 deletions

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..b557ada
--- /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 crcSums 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 );
+	}		
+}