core/plugins/org.eclipse.dltk.ui/core refactoring/org/eclipse/dltk/internal/corext/refactoring/reorg/ModelElementTransfer.java

/*******************************************************************************
 * Copyright (c) 2000, 2017 IBM Corporation and others.
 * 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.dltk.internal.corext.refactoring.reorg;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

import org.eclipse.dltk.core.DLTKCore;
import org.eclipse.dltk.core.IModelElement;
import org.eclipse.swt.dnd.ByteArrayTransfer;
import org.eclipse.swt.dnd.TransferData;

public class ModelElementTransfer extends ByteArrayTransfer {

	/**
	 * Singleton instance.
	 */
	private static final ModelElementTransfer fInstance = new ModelElementTransfer();

	// Create a unique ID to make sure that different Eclipse
	// applications use different "types" of <code>ScriptElementTransfer</code>
	private static final String TYPE_NAME = "model-element-transfer-format:" //$NON-NLS-1$
			+ System.currentTimeMillis() + ":" + fInstance.hashCode(); //$NON-NLS-1$

	private static final int TYPEID = registerType(TYPE_NAME);

	private ModelElementTransfer() {
	}

	/**
	 * Returns the singleton instance.
	 *
	 * @return the singleton instance
	 */
	public static ModelElementTransfer getInstance() {
		return fInstance;
	}

	@Override
	protected int[] getTypeIds() {
		return new int[] { TYPEID };
	}

	@Override
	protected String[] getTypeNames() {
		return new String[] { TYPE_NAME };
	}

	@Override
	protected void javaToNative(Object data, TransferData transferData) {
		if (!(data instanceof IModelElement[]))
			return;

		IModelElement[] modelElements = (IModelElement[]) data;
		/*
		 * The element serialization format is: (int) number of element Then,
		 * the following for each element: (String) handle identifier
		 */

		try (ByteArrayOutputStream out = new ByteArrayOutputStream();
				DataOutputStream dataOut = new DataOutputStream(out)) {

			// write the number of elements
			dataOut.writeInt(modelElements.length);

			// write each element
			for (int i = 0; i < modelElements.length; i++) {
				writeScriptElement(dataOut, modelElements[i]);
			}

			byte[] bytes = out.toByteArray();
			super.javaToNative(bytes, transferData);
		} catch (IOException e) {
			// it's best to send nothing if there were problems
		}
	}

	@Override
	protected Object nativeToJava(TransferData transferData) {
		/*
		 * The element serialization format is: (int) number of element Then,
		 * the following for each element: (String) handle identifier
		 */

		byte[] bytes = (byte[]) super.nativeToJava(transferData);
		if (bytes == null)
			return null;
		DataInputStream in = new DataInputStream(
				new ByteArrayInputStream(bytes));
		try {
			int count = in.readInt();
			IModelElement[] results = new IModelElement[count];
			for (int i = 0; i < count; i++) {
				results[i] = readScriptElement(in);
			}
			return results;
		} catch (IOException e) {
			return null;
		}
	}

	private IModelElement readScriptElement(DataInputStream dataIn)
			throws IOException {
		String handleIdentifier = dataIn.readUTF();
		return DLTKCore.create(handleIdentifier);
	}

	private static void writeScriptElement(DataOutputStream dataOut,
			IModelElement element) throws IOException {
		dataOut.writeUTF(element.getHandleIdentifier());
	}
}