Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2012 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.ole.win32.*; import org.eclipse.swt.internal.win32.*; /** * 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 < 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() > 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]; data[i].formatetc = new FORMATETC(); data[i].formatetc.cfFormat = types[i]; data[i].formatetc.dwAspect = COM.DVASPECT_CONTENT; data[i].formatetc.lindex = -1; data[i].formatetc.tymed = COM.TYMED_HGLOBAL; } return data; } @Override public boolean isSupportedType(TransferData transferData) { if (transferData == null) return false; int[] types = getTypeIds(); for (int i = 0; i < types.length; i++) { FORMATETC format = transferData.formatetc; if (format.cfFormat == types[i] && (format.dwAspect & COM.DVASPECT_CONTENT) == COM.DVASPECT_CONTENT && (format.tymed & COM.TYMED_HGLOBAL) == COM.TYMED_HGLOBAL) 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) { if (!checkByteArray(object) || !isSupportedType(transferData)) { DND.error(DND.ERROR_INVALID_DATA); } // Allocate the memory because the caller (DropTarget) has not handed it in // The caller of this method must release the data when it is done with it. byte[] data = (byte[]) object; int size = data.length; long newPtr = OS.GlobalAlloc(OS.GMEM_FIXED | OS.GMEM_ZEROINIT, size); OS.MoveMemory(newPtr, data, size); transferData.stgmedium = new STGMEDIUM(); transferData.stgmedium.tymed = COM.TYMED_HGLOBAL; transferData.stgmedium.unionField = newPtr; transferData.stgmedium.pUnkForRelease = 0; transferData.result = COM.S_OK; } /** * 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.pIDataObject == 0) return null; IDataObject data = new IDataObject(transferData.pIDataObject); data.AddRef(); FORMATETC formatetc = transferData.formatetc; STGMEDIUM stgmedium = new STGMEDIUM(); stgmedium.tymed = COM.TYMED_HGLOBAL; transferData.result = getData(data, formatetc, stgmedium); data.Release(); if (transferData.result != COM.S_OK) return null; long hMem = stgmedium.unionField; int size = OS.GlobalSize(hMem); byte[] buffer = new byte[size]; long ptr = OS.GlobalLock(hMem); OS.MoveMemory(buffer, ptr, size); OS.GlobalUnlock(hMem); OS.GlobalFree(hMem); return buffer; } boolean checkByteArray(Object object) { return (object != null && object instanceof byte[] && ((byte[]) object).length > 0); } }