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>TextTransfer</code> provides a platform specific mechanism * for converting plain text represented as a java <code>String</code> * to a platform specific representation of the data and vice versa. * * <p>An example of a java <code>String</code> containing plain text is shown * below:</p> * * <pre><code> * String textData = "Hello World"; * </code></pre> * * <p>Note the <code>TextTransfer</code> does not change the content of the text * data. For a better integration with the platform, the application should convert * the line delimiters used in the text data to the standard line delimiter used by the * platform. * </p> * * @see Transfer */ public class TextTransfer extends ByteArrayTransfer { private static TextTransfer _instance = new TextTransfer(); private static final String CF_UNICODETEXT = "CF_UNICODETEXT"; //$NON-NLS-1$ private static final String CF_TEXT = "CF_TEXT"; //$NON-NLS-1$ private static final int CF_UNICODETEXTID = COM.CF_UNICODETEXT; private static final int CF_TEXTID = COM.CF_TEXT; private TextTransfer() { } /** * Returns the singleton instance of the TextTransfer class. * * @return the singleton instance of the TextTransfer class */ public static TextTransfer getInstance() { return _instance; } /** * This implementation of <code>javaToNative</code> converts plain text * represented by a java <code>String</code> to a platform specific representation. * * @param object a java <code>String</code> containing text * @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 public void javaToNative(Object object, TransferData transferData) { if (!checkText(object) || !isSupportedType(transferData)) { DND.error(DND.ERROR_INVALID_DATA); } transferData.result = COM.E_FAIL; String string = (String) object; switch (transferData.type) { case COM.CF_UNICODETEXT: { int charCount = string.length(); char[] chars = new char[charCount + 1]; string.getChars(0, charCount, chars, 0); int byteCount = chars.length * 2; long newPtr = OS.GlobalAlloc(COM.GMEM_FIXED | COM.GMEM_ZEROINIT, byteCount); OS.MoveMemory(newPtr, chars, byteCount); transferData.stgmedium = new STGMEDIUM(); transferData.stgmedium.tymed = COM.TYMED_HGLOBAL; transferData.stgmedium.unionField = newPtr; transferData.stgmedium.pUnkForRelease = 0; transferData.result = COM.S_OK; break; } case COM.CF_TEXT: { int count = string.length(); char[] chars = new char[count + 1]; string.getChars(0, count, chars, 0); int codePage = OS.GetACP(); int cchMultiByte = OS.WideCharToMultiByte(codePage, 0, chars, -1, null, 0, null, null); if (cchMultiByte == 0) { transferData.stgmedium = new STGMEDIUM(); transferData.result = COM.DV_E_STGMEDIUM; return; } long lpMultiByteStr = OS.GlobalAlloc(COM.GMEM_FIXED | COM.GMEM_ZEROINIT, cchMultiByte); OS.WideCharToMultiByte(codePage, 0, chars, -1, lpMultiByteStr, cchMultiByte, null, null); transferData.stgmedium = new STGMEDIUM(); transferData.stgmedium.tymed = COM.TYMED_HGLOBAL; transferData.stgmedium.unionField = lpMultiByteStr; transferData.stgmedium.pUnkForRelease = 0; transferData.result = COM.S_OK; break; } } return; } /** * This implementation of <code>nativeToJava</code> converts a platform specific * representation of plain text to a java <code>String</code>. * * @param transferData the platform specific representation of the data to be converted * @return a java <code>String</code> containing text if the conversion was successful; otherwise null * * @see Transfer#javaToNative */ @Override public 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; try { switch (transferData.type) { case CF_UNICODETEXTID: { /* Ensure byteCount is a multiple of 2 bytes */ int size = OS.GlobalSize(hMem) / 2 * 2; if (size == 0) return null; char[] chars = new char[size / 2]; long ptr = OS.GlobalLock(hMem); if (ptr == 0) return null; try { OS.MoveMemory(chars, ptr, size); int length = chars.length; for (int i = 0; i < chars.length; i++) { if (chars[i] == '\0') { length = i; break; } } return new String(chars, 0, length); } finally { OS.GlobalUnlock(hMem); } } case CF_TEXTID: { long lpMultiByteStr = OS.GlobalLock(hMem); if (lpMultiByteStr == 0) return null; try { int codePage = OS.GetACP(); int cchWideChar = OS.MultiByteToWideChar(codePage, OS.MB_PRECOMPOSED, lpMultiByteStr, -1, null, 0); if (cchWideChar == 0) return null; char[] lpWideCharStr = new char[cchWideChar - 1]; OS.MultiByteToWideChar(codePage, OS.MB_PRECOMPOSED, lpMultiByteStr, -1, lpWideCharStr, lpWideCharStr.length); return new String(lpWideCharStr); } finally { OS.GlobalUnlock(hMem); } } } } finally { OS.GlobalFree(hMem); } return null; } @Override protected int[] getTypeIds() { return new int[] { CF_UNICODETEXTID, CF_TEXTID }; } @Override protected String[] getTypeNames() { return new String[] { CF_UNICODETEXT, CF_TEXT }; } boolean checkText(Object object) { return (object != null && object instanceof String && ((String) object).length() > 0); } @Override protected boolean validate(Object object) { return checkText(object); } }