allow multiple loading of same format

plugins/com.minres.scviewer.database.text/src/com/minres/scviewer/database/text/TextDbLoaderFactory.java

@@ -0,0 +1,77 @@
+/*******************************************************************************
+ * Copyright (c) 2012 IT Just working.
+ * Copyright (c) 2020 MINRES Technologies GmbH
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IT Just working - initial API and implementation
+ *******************************************************************************/
+package com.minres.scviewer.database.text;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.zip.GZIPInputStream;
+
+import com.minres.scviewer.database.IWaveformDbLoader;
+import com.minres.scviewer.database.IWaveformDbLoaderFactory;
+
+/**
+ * The Class TextDbLoader.
+ */
+public class TextDbLoaderFactory implements IWaveformDbLoaderFactory {
+
+	/** The Constant x. */
+	static final byte[] x = "scv_tr_stream".getBytes();
+
+	/**
+	 * Checks if f is gzipped.
+	 *
+	 * @param f the f
+	 * @return true, if is gzipped
+	 */
+	private static boolean isGzipped(File f) {
+		try (InputStream is = new FileInputStream(f)) {
+			byte[] signature = new byte[2];
+			int nread = is.read(signature); // read the gzip signature
+			return nread == 2 && signature[0] == (byte) 0x1f && signature[1] == (byte) 0x8b;
+		} catch (IOException e) {
+			return false;
+		}
+	}
+
+	/**
+	 * Can load.
+	 *
+	 * @param inputFile the input file
+	 * @return true, if successful
+	 */
+	@Override
+	public boolean canLoad(File inputFile) {
+		if (!inputFile.isDirectory() && inputFile.exists()) {
+			boolean gzipped = isGzipped(inputFile);
+			try(InputStream stream = gzipped ? new GZIPInputStream(new FileInputStream(inputFile)) : new FileInputStream(inputFile)){
+				byte[] buffer = new byte[x.length];
+				int readCnt = stream.read(buffer, 0, x.length);
+				if (readCnt == x.length) {
+					for (int i = 0; i < x.length; i++)
+						if (buffer[i] != x[i])
+							return false;
+				}
+				return true;
+			} catch (Exception e) {
+				return false;
+			}
+		}
+		return false;
+	}
+
+	@Override
+	public IWaveformDbLoader getLoader() {
+		return new TextDbLoader();
+	}
+}