Improve BSTR Handling

CHANGES.md

@@ -61,6 +61,7 @@ Bug Fixes
 * [#601](https://github.com/java-native-access/jna/pull/601): Remove COMThread and COM initialization from objects and require callers to initialize COM themselves. Asserts are added to guard correct usage. - [@matthiasblaesing](https://github.com/matthiasblaesing).
 * [#602](https://github.com/java-native-access/jna/pull/602): Make sure SID related memory is properly released once no longer required [@lgoldstein](https://github.com/lgoldstein).
 * [#610](https://github.com/java-native-access/jna/pull/610): Fixed issue #604: Kernel32#GetLastError() always returns ERROR_SUCCESS [@lgoldstein](https://github.com/lgoldstein).
+* [#634](https://github.com/java-native-access/jna/pull/634): Improve BSTR handling - [@matthiasblaesing](https://github.com/matthiasblaesing).
 
 Release 4.2.1
 =============

contrib/platform/src/com/sun/jna/platform/win32/COM/IMoniker.java

@@ -13,8 +13,6 @@
 package com.sun.jna.platform.win32.COM;
 
 import com.sun.jna.Pointer;
-import com.sun.jna.platform.win32.WTypes.BSTRByReference;
-import com.sun.jna.platform.win32.WinNT.HRESULT;
 
 
 /**
@@ -81,7 +79,7 @@ public interface IMoniker extends IPersistStream {
          * 
 	 * @see <a href="http://msdn.microsoft.com/en-us/library/windows/desktop/ms680754%28v=vs.85%29.aspx">MSDN</a>
 	 */
-	HRESULT GetDisplayName(Pointer pbc, Pointer pmkToLeft, BSTRByReference ppszDisplayName);
+	String GetDisplayName(Pointer bindContext, Pointer pmkToLeft);
 
 	void ParseDisplayName();
 

contrib/platform/src/com/sun/jna/platform/win32/COM/Moniker.java

@@ -14,10 +14,11 @@
 
 import com.sun.jna.Pointer;
 import com.sun.jna.Structure;
-import com.sun.jna.platform.win32.WTypes.BSTRByReference;
 import com.sun.jna.platform.win32.WinNT;
 import com.sun.jna.platform.win32.Guid.CLSID;
-import com.sun.jna.platform.win32.WinNT.HRESULT;
+import com.sun.jna.platform.win32.Ole32;
+import com.sun.jna.platform.win32.WTypes;
+import com.sun.jna.ptr.PointerByReference;
 
 public class Moniker extends Unknown implements IMoniker {
 
@@ -119,13 +120,26 @@ public void RelativePathTo() {
 	}
 
 	@Override
-	public HRESULT GetDisplayName(Pointer pbc, Pointer pmkToLeft, BSTRByReference ppszDisplayName) {
+	public String GetDisplayName(Pointer pbc, Pointer pmkToLeft) {
 		final int vTableId = vTableIdStart + 13;
 
+                PointerByReference ppszDisplayNameRef = new PointerByReference();
+
 		WinNT.HRESULT hr = (WinNT.HRESULT) this._invokeNativeObject(vTableId, new Object[] { this.getPointer(), pbc,
-				pmkToLeft, ppszDisplayName }, WinNT.HRESULT.class);
+				pmkToLeft, ppszDisplayNameRef }, WinNT.HRESULT.class);
 
-		return hr;
+                COMUtils.checkRC(hr);
+
+                Pointer ppszDisplayName = ppszDisplayNameRef.getValue();
+                if(ppszDisplayName == null) {
+                    return null;
+                }
+
+                WTypes.LPOLESTR oleStr = new WTypes.LPOLESTR(ppszDisplayName);
+                String name = oleStr.getValue();
+                Ole32.INSTANCE.CoTaskMemFree(ppszDisplayName);
+
+		return name;
 	}
 
 	@Override

contrib/platform/src/com/sun/jna/platform/win32/OleAuto.java

@@ -121,6 +121,22 @@ public interface OleAuto extends StdCallLibrary {
 	 */
 	void SysFreeString(BSTR bstr);
 
+	/**
+	 * Returns the length (in bytes) of a BSTR.
+	 *
+	 * @param bstr
+	 *            Unicode string that was allocated previously.
+	 */
+	int SysStringByteLen(BSTR bstr);
+
+	/**
+	 * Returns the length of a BSTR.
+	 *
+	 * @param bstr
+	 *            Unicode string that was allocated previously.
+	 */
+	int SysStringLen(BSTR bstr);
+
 	/**
 	 * The VariantInit function initializes the VARIANTARG by setting the vt
 	 * field to VT_EMPTY. Unlike VariantClear, this function does not interpret

contrib/platform/src/com/sun/jna/platform/win32/WTypes.java

@@ -22,6 +22,9 @@
 import com.sun.jna.Structure;
 import com.sun.jna.platform.win32.WinDef.USHORT;
 import com.sun.jna.ptr.ByReference;
+import java.io.UnsupportedEncodingException;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 /**
  * Constant defined in WTypes.h
@@ -61,35 +64,80 @@ public interface WTypes {
     public static int CLSCTX_ALL = CLSCTX_INPROC_SERVER | CLSCTX_INPROC_HANDLER
             | CLSCTX_LOCAL_SERVER;
 
+    /**
+     * BSTR wrapper.
+     * 
+     * <p>From MSDN:</p>
+     * 
+     * <blockquote>A BSTR (Basic string or binary string) is a string data type 
+     * that is used by COM, Automation, and Interop functions. Use the BSTR data 
+     * type in all interfaces that will be accessed from script.</blockquote>
+     * 
+     * <p>The memory structure:</p>
+     * 
+     * <dl>
+     * <dt>Length prefix</dt>
+     * <dd>Length of the data array holding the string data and does not include
+     * the final two NULL characters.</dd>
+     * <dt>Data string</dt>
+     * <dd>UTF-16LE encoded bytes for the string.</dd>
+     * <dt>Terminator</dt>
+     * <dd>Two null characters</dd>
+     * </dl>
+     * 
+     * <p>The "value" of the BSTR is the pointer to the start of the Data String,
+     * the length prefix is the four bytes before that.</p>
+     * 
+     * <p>The MSDN states, that a BSTR derived from a Nullpointer is treated
+     * as a string containing zero characters.</p>
+     */
     public static class BSTR extends PointerType {
         public static class ByReference extends BSTR implements
                 Structure.ByReference {
         }
 
         public BSTR() {
-            super(new Memory(Pointer.SIZE));
+            super(Pointer.NULL);
         }
 
         public BSTR(Pointer pointer) {
             super(pointer);
         }
 
         public BSTR(String value) {
-            super(new Memory((value.length() + 1L) * Native.WCHAR_SIZE));
+            super();
             this.setValue(value);
         }
 
         public void setValue(String value) {
-            this.getPointer().setWideString(0, value);
+            if(value == null) {
+                value = "";
+            }
+            try {
+                byte[] encodedValue = value.getBytes("UTF-16LE");
+                // 4 bytes for the length prefix, length for the encoded data,
+                // 2 bytes for the two NULL terminators
+                Memory mem = new Memory(4 + encodedValue.length + 2);
+                mem.clear();
+                mem.setInt(0, encodedValue.length);
+                mem.write(4, encodedValue, 0, encodedValue.length);
+                this.setPointer(mem.share(4));
+            } catch (UnsupportedEncodingException ex) {
+                throw new RuntimeException("UTF-16LE charset is not supported", ex);
+            }
         }
 
         public String getValue() {
-            Pointer pointer = this.getPointer();
-            String str = null;
-            if (pointer != null)
-                str = pointer.getWideString(0);
-
-            return str;
+            try {
+                Pointer pointer = this.getPointer();
+                if(pointer == null) {
+                    return "";
+                }
+                int stringLength = pointer.getInt(-4);
+                return new String(pointer.getByteArray(0, stringLength), "UTF-16LE");
+            } catch (UnsupportedEncodingException ex) {
+                throw new RuntimeException("UTF-16LE charset is not supported", ex);
+            }
         }
 
         @Override

contrib/platform/test/com/sun/jna/platform/win32/COM/RunningObjectTable_Test.java

@@ -21,6 +21,7 @@
 
 import com.sun.jna.platform.win32.Ole32;
 import com.sun.jna.platform.win32.Guid.REFIID;
+import com.sun.jna.platform.win32.WTypes;
 import com.sun.jna.platform.win32.WTypes.BSTRByReference;
 import com.sun.jna.platform.win32.WinDef.DWORD;
 import com.sun.jna.platform.win32.WinDef.ULONG;
@@ -114,13 +115,8 @@ public void GetObject() {
 
 			PointerByReference ppbc = new PointerByReference();
 			Ole32.INSTANCE.CreateBindCtx(new DWORD(), ppbc);
-			//IBindCtx pbc = new BindCtx(ppbc.getValue());
-
-			BSTRByReference ppszDisplayName = new BSTRByReference();
-			hr = moniker.GetDisplayName(ppbc.getValue(), moniker.getPointer(), ppszDisplayName);
-			COMUtils.checkRC(hr);
-			String name = ppszDisplayName.getString();
-			Ole32.INSTANCE.CoTaskMemFree(ppszDisplayName.getPointer().getPointer(0));
+
+			String name = moniker.GetDisplayName(ppbc.getValue(), moniker.getPointer());
 
 			PointerByReference ppunkObject = new PointerByReference();
 			hr = rot.GetObject(moniker.getPointer(), ppunkObject);

contrib/platform/test/com/sun/jna/platform/win32/WTypesTest.java

@@ -15,6 +15,7 @@
 import com.sun.jna.Memory;
 import com.sun.jna.Native;
 import com.sun.jna.Pointer;
+import com.sun.jna.platform.win32.WTypes.BSTR;
 import junit.framework.TestCase;
 
 public class WTypesTest extends TestCase {
@@ -53,7 +54,45 @@ public void testLPWSTRConstruction() {
         WTypes.LPWSTR fromPointer = new WTypes.LPWSTR(TEST_POINTER);
         assertEquals(fromPointer.getValue(), TEST_STRING);
     }
+
+    public void testBSTRBasic() {
+        String demoString = "input\u00D6\u00E4\u00DC?!";
+        // Allocation via system and the "correct" way
+        BSTR sysAllocated = OleAuto.INSTANCE.SysAllocString(demoString);
+        // Java based allocation - not suitable if passed via automation
+        BSTR javaAllocated = new BSTR(demoString);
+
+        // Ensure encoding roundtripping works
+        assertEquals(demoString, sysAllocated.getValue());
+        assertEquals(demoString, javaAllocated.getValue());
+
+        // BSTR is encoded as UTF-16/UCS2, so byte length is 2 * char count
+        assertEquals(demoString.length(), OleAuto.INSTANCE.SysStringLen(sysAllocated));
+        assertEquals(demoString.length(), OleAuto.INSTANCE.SysStringLen(javaAllocated));
+        assertEquals(2 * demoString.length(), OleAuto.INSTANCE.SysStringByteLen(sysAllocated));
+        assertEquals(2 * demoString.length(), OleAuto.INSTANCE.SysStringByteLen(javaAllocated));        
+
+        // The BSTR Pointer points 4 bytes into the data itself (beginning of data
+        // string, the 4 preceding bytes code the string length (in bytes)
+        assertEquals(2 * demoString.length(), sysAllocated.getPointer().getInt(-4));
+        assertEquals(2 * demoString.length(), javaAllocated.getPointer().getInt(-4));
+
+        OleAuto.INSTANCE.SysFreeString(sysAllocated);
+        // javaAllocated is allocated via Memory and will be freeed by the
+        // garbadge collector automaticly
+    }
 
+    public void testBSTRNullPointerHandling() {
+        // Allocation from NULL should return NULL
+        BSTR sysAllocated = OleAuto.INSTANCE.SysAllocString(null);
+        assertNull(sysAllocated);
+
+        // MSDN states, that the BSTR from Nullpointer represents the string with
+        // zero characters
+        BSTR bstr = new BSTR(Pointer.NULL);
+        assertEquals("", bstr.getValue());
+    }
+
     public static void main(String[] args) {
         junit.textui.TestRunner.run(WTypesTest.class);
     }