bundles/org.eclipse.swt/Eclipse SWT Drag and Drop/gtk/org/eclipse/swt/dnd/ByteArrayTransfer.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 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.dnd;

import org.eclipse.swt.internal.*;
import org.eclipse.swt.internal.gtk.*;

/**
 * The class <code>ByteArrayTransfer</code> provides a platform specific
 * mechanism for converting a java <code>byte[]</code> to a platform
 * specific representation of the byte array and vice versa.
 *
 * <p><code>ByteArrayTransfer</code> is never used directly but is sub-classed
 * by transfer agents that convert between data in a java format such as a
 * <code>String</code> and a platform specific byte array.
 *
 * <p>If the data you are converting <b>does not</b> map to a
 * <code>byte[]</code>, you should sub-class <code>Transfer</code> directly
 * and do your own mapping to a platform data type.</p>
 *
 * <p>The following snippet shows a subclass of ByteArrayTransfer that transfers
 * data defined by the class <code>MyType</code>.</p>
 *
 * <pre><code>
 * public class MyType {
 *	public String fileName;
 *	public long fileLength;
 *	public long lastModified;
 * }
 * </code></pre>
 *
 * <pre><code>
 * public class MyTypeTransfer extends ByteArrayTransfer {
 *
 *	private static final String MYTYPENAME = "my_type_name";
 *	private static final int MYTYPEID = registerType(MYTYPENAME);
 *	private static MyTypeTransfer _instance = new MyTypeTransfer();
 *
 * private MyTypeTransfer() {}
 *
 * public static MyTypeTransfer getInstance () {
 * 	return _instance;
 * }
 * public void javaToNative (Object object, TransferData transferData) {
 * 	if (object == null || !(object instanceof MyType[])) return;
 *
 * 	if (isSupportedType(transferData)) {
 * 		MyType[] myTypes = (MyType[]) object;
 * 		try {
 * 			// write data to a byte array and then ask super to convert to pMedium
 * 			ByteArrayOutputStream out = new ByteArrayOutputStream();
 * 			DataOutputStream writeOut = new DataOutputStream(out);
 * 			for (int i = 0, length = myTypes.length; i &lt; length;  i++){
 * 				byte[] buffer = myTypes[i].fileName.getBytes();
 * 				writeOut.writeInt(buffer.length);
 * 				writeOut.write(buffer);
 * 				writeOut.writeLong(myTypes[i].fileLength);
 * 				writeOut.writeLong(myTypes[i].lastModified);
 * 			}
 * 			byte[] buffer = out.toByteArray();
 * 			writeOut.close();
 *
 * 			super.javaToNative(buffer, transferData);
 *
 * 		} catch (IOException e) {
 * 		}
 * 	}
 * }
 * public Object nativeToJava(TransferData transferData){
 *
 * 	if (isSupportedType(transferData)) {
 *
 * 		byte[] buffer = (byte[])super.nativeToJava(transferData);
 * 		if (buffer == null) return null;
 *
 * 		MyType[] myData = new MyType[0];
 * 		try {
 * 			ByteArrayInputStream in = new ByteArrayInputStream(buffer);
 * 			DataInputStream readIn = new DataInputStream(in);
 * 			while(readIn.available() &gt; 20) {
 * 				MyType datum = new MyType();
 * 				int size = readIn.readInt();
 * 				byte[] name = new byte[size];
 * 				readIn.read(name);
 * 				datum.fileName = new String(name);
 * 				datum.fileLength = readIn.readLong();
 * 				datum.lastModified = readIn.readLong();
 * 				MyType[] newMyData = new MyType[myData.length + 1];
 * 				System.arraycopy(myData, 0, newMyData, 0, myData.length);
 * 				newMyData[myData.length] = datum;
 * 				myData = newMyData;
 * 			}
 * 			readIn.close();
 * 		} catch (IOException ex) {
 * 			return null;
 * 		}
 * 		return myData;
 * 	}
 *
 * 	return null;
 * }
 * protected String[] getTypeNames(){
 * 	return new String[]{MYTYPENAME};
 * }
 * protected int[] getTypeIds(){
 * 	return new int[] {MYTYPEID};
 * }
 * }
 * </code></pre>
 *
 * @see Transfer
 */
public abstract class ByteArrayTransfer extends Transfer {

@Override
public TransferData[] getSupportedTypes() {
	int[] types = getTypeIds();
	TransferData[] data = new TransferData[types.length];
	for (int i = 0; i < types.length; i++) {
		data[i] = new TransferData();
		data[i].type = types[i];
	}
	return data;
}

@Override
public boolean isSupportedType(TransferData transferData){
	if (transferData == null) return false;
	int[] types = getTypeIds();
	for (int i = 0; i < types.length; i++) {
		if (transferData.type == types[i]) return true;
	}
	return false;
}

/**
 * This implementation of <code>javaToNative</code> converts a java
 * <code>byte[]</code> to a platform specific representation.
 *
 * @param object a java <code>byte[]</code> containing the data to be converted
 * @param transferData an empty <code>TransferData</code> object that will
 *  	be filled in on return with the platform specific format of the data
 *
 * @see Transfer#nativeToJava
 */
@Override
protected void javaToNative (Object object, TransferData transferData) {
	transferData.result = 0;
	if (!checkByteArray(object) || !isSupportedType(transferData)) {
		DND.error(DND.ERROR_INVALID_DATA);
	}
	byte[] buffer = (byte[])object;
	if (buffer.length == 0) return;
	long /*int*/ pValue = OS.g_malloc(buffer.length);
	if (pValue == 0) return;
	C.memmove(pValue, buffer, buffer.length);
	transferData.length = buffer.length;
	transferData.format = 8;
	transferData.pValue = pValue;
	transferData.result = 1;
}

/**
 * This implementation of <code>nativeToJava</code> converts a platform specific
 * representation of a byte array to a java <code>byte[]</code>.
 *
 * @param transferData the platform specific representation of the data to be converted
 * @return a java <code>byte[]</code> containing the converted data if the conversion was
 * 		successful; otherwise null
 *
 * @see Transfer#javaToNative
 */
@Override
protected Object nativeToJava(TransferData transferData) {
	if ( !isSupportedType(transferData) || transferData.pValue == 0) return null;
	int size = transferData.format * transferData.length / 8;
	if (size == 0) return null;
	byte[] buffer = new byte[size];
	C.memmove(buffer, transferData.pValue, size);
	return buffer;
}

boolean checkByteArray(Object object) {
	return (object != null && object instanceof byte[] && ((byte[])object).length > 0);
}
}