ByteArrayTransfer provides a platform specific
+ * mechanism for converting a java byte[] to a platform
+ * specific representation of the byte array and vice versa.
+ *
+ * ByteArrayTransfer is never used directly but is sub-classed
+ * by transfer agents that convert between data in a java format such as a
+ * String and a platform specific byte array.
+ *
+ *
If the data you are converting does not map to a
+ * byte[], you should sub-class Transfer directly
+ * and do your own mapping to a platform data type.
The following snippet shows a subclass of ByteArrayTransfer that transfers
+ * data defined by the class MyType.
+ * public class MyType {
+ * public String fileName;
+ * public long fileLength;
+ * public long lastModified;
+ * }
+ *
+ * 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};
+ * }
+ * }
+ * javaToNative converts a java
+ * byte[] to a platform specific representation.
+ *
+ * @param object a java byte[] containing the data to be converted
+ * @param transferData an empty TransferData 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 nativeToJava converts a platform specific
+ * representation of a byte array to a java byte[].
+ *
+ * @param transferData the platform specific representation of the data to be converted
+ * @return a java byte[] 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);
+}
+}