src/main/java/org/eclipse/mdm/openatfx/mdf/mdf3/Mdf3Util.java

/********************************************************************************
 * Copyright (c) 2015-2018 Contributors to the Eclipse Foundation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 ********************************************************************************/


package org.eclipse.mdm.openatfx.mdf.mdf3;

import java.io.IOException;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.channels.SeekableByteChannel;

/**
 * Utility class having methods to read MDF3 file contents.
 *
 * @author Christian Rechner
 */
abstract class Mdf3Util {

	private static final String CHARSET_ISO8859 = "ISO-8859-1";

	public static String readChars(SeekableByteChannel channel, int length) throws IOException {
		ByteBuffer bb = ByteBuffer.allocate(length);
		bb.order(ByteOrder.LITTLE_ENDIAN);
		channel.read(bb);
		bb.rewind();
		return readChars(bb, bb.remaining());
	}

	public static String readChars(ByteBuffer bb, int length) throws IOException {
		byte[] b = new byte[length];
		bb.get(b);

		// lookup null character for string termination
		int strLength = 0;
		for (byte element : b) {
			if (element == 0) {
				break;
			}
			strLength++;
		}

		return new String(b, 0, strLength, CHARSET_ISO8859);
	}

	public static double readReal(ByteBuffer bb) throws IOException {
		return bb.getDouble();
	}

	public static boolean readBool(ByteBuffer bb) throws IOException {
		return bb.getShort() > 0;
	}

	public static BigInteger readUInt64(ByteBuffer bb) {
		byte[] data = new byte[8];
		bb.get(data);
		long l1 = ((long) data[0] & 0xff) << 0 | ((long) data[1] & 0xff) << 8 | ((long) data[2] & 0xff) << 16
				| ((long) data[3] & 0xff) << 24;
		long l2 = ((long) data[4] & 0xff) << 0 | ((long) data[5] & 0xff) << 8 | ((long) data[6] & 0xff) << 16
				| ((long) data[7] & 0xff) << 24;
		return BigInteger.valueOf(l1 << 0 | l2 << 32);
	}

	public static long readUInt32(ByteBuffer bb) throws IOException {
		return bb.getInt() & 0xffffffffL;
	}

	public static int readUInt16(ByteBuffer bb) throws IOException {
		return bb.getShort() & 0xffff;
	}

	public static int readInt16(ByteBuffer bb) throws IOException {
		return bb.getShort();
	}

	public static long readLink(ByteBuffer bb) throws IOException {
		return bb.getInt() & 0xffffffffL;
	}

}