Initial source import.

src/mightypork/utils/files/InstanceLock.java

@@ -0,0 +1,54 @@
+package mightypork.utils.files;
+
+
+import java.io.File;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.channels.FileLock;
+
+
+/**
+ * Instance lock (avoid running twice)
+ * 
+ * @author Ondřej Hruška (MightyPork)
+ */
+public class InstanceLock {
+	
+	@SuppressWarnings("resource")
+	public static boolean onFile(final File lockFile)
+	{
+		try {
+			lockFile.getParentFile().mkdirs();
+			final RandomAccessFile randomAccessFile = new RandomAccessFile(lockFile, "rw");
+			
+			final FileLock fileLock = randomAccessFile.getChannel().tryLock();
+			if (fileLock != null) {
+				
+				Runtime.getRuntime().addShutdownHook(new Thread() {
+					
+					@Override
+					public void run()
+					{
+						try {
+							fileLock.release();
+							randomAccessFile.close();
+							if (!lockFile.delete()) throw new IOException();
+						} catch (final Throwable t) {
+							System.err.println("Unable to remove lock file.");
+							t.printStackTrace();
+						}
+					}
+				});
+				
+				return true;
+			}
+			
+			return false;
+		} catch (final IOException e) {
+			System.err.println("IO error while obtaining lock.");
+			e.printStackTrace();
+			return false;
+		}
+	}
+	
+}