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List:       ms-java-com
Subject:    jactivex generates "type=PTR" instead of "ARRAY" for returned enum
From:       Carl Clefstad <carl.clefstad () SANDIEGOCA ! NCR ! COM>
Date:       1999-01-30 1:18:16
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Can some please explain this:
I have a COM method that returns an "enum" value.  I call this method from Java.
When I use the 'retval' IDL attribute, everything works fine, but when I omit
it and try to return the value as a parameter, I get (after changing my Java
code as needed) a runtime "java.lang.OutOfMemoryError" on the  method call.

The IDL looks something like this:
========================
 typedef enum tagCOLOR
 {
  UNKNOWN = 0,
      RED,
  GREEN,
  BLUE,
                ... (actually has about 36 items in the list
 } COLOR;

 interface IColored : IUnknown
 {
  HRESULT GetColor( [out, retval] COLOR* piStatus );
 }
 coclass Thing
 {
  [default] interface IColored;
   }
========================


The C++ implementation looks something like this:
========================
HRESULT CThing::GetColor( COLOR* piColor )
{
  if( piColor == NULL )
   return E_POINTER;
  *piColor = m_iMyColor;

  // Return indication if color is florescent
  if( m_bFlorescent )
   return S_FALSE;

  return S_OK;
}
========================


When I run jactivex, it generates:
========================
// Auto-generated using JActiveX.EXE 5.00.2924
//   (jactivex    /javatlb  MyServer.tlb )
...
package xyx;
...
// VTable-only interface IColored
/** @com.interface(iid=56632866-0FB2-11D2-9227-00E0290899BF, thread=AUTO) */
public interface IMCChassis extends IUnknown
{
  /** @com.method(vtoffset=4)
      @com.parameters([type=I4] return) */
  public int GetColor();
...
}
========================


In Java, I call it like so:
========================
  int color = tagCOLOR.UNKNOWN;
  boolean florescent = false;
  try {
   color = iColored.GetColor();
  } catch (ComSuccessException e) {
   // S_FALSE returned ... "color" contains a florescent color
   // is color set?
   System.out.println("getColor returned S_FALSE, color is florescent");
   florescent = true;
  } catch (ComFailException e) {
   // handle error
  }
  System.out.println("GetColor returned: " + color);
========================


That works fine (except I can't get florescent colors because the returned
color when ComSuccessException is thrown will not be set!).

Here's the main problem:  When I omit 'retval' from the IDL (because I want
to see if I can get florescent colors returned), the Java stub and my code
change as shown below ... but I always get a "java.lang.OutOfMemoryError" at
runtime during the call to GetColor().

New jactivex-generated Java stub:
========================
  /** @com.method(vtoffset=4)
      @com.parameters([out,type=PTR] piColor) */
  public void GetColor(int[] piColor);
========================


My new Java code:
========================
  int[] color = new int[1]; color[0] = tagCOLOR.UNKNOWN;
  boolean florescent = false;
  try {
   iColored.GetColor(color);  // <- throws OutOfMemoryError!!!
  } catch (ComSuccessException e) {
   // S_FALSE returned ... "color" contains a florescent color
   // is color set?
   System.out.println("getColor returned S_FALSE, color is florescent");
   florescent = true;
  } catch (ComFailException e) {
   // handle error
  }
  System.out.println("GetColor returned: " + color[0]);
========================

If I hand-edit the jactivex-generated Java stub, changing:
      @com.parameters([out,type=PTR] piColor) */
to:
      @com.parameters([out,size=1,type=ARRAY] piColor) */
then it works (and my 'florescent color' gets returned correctly).

Why does jactivex generate "type=PTR" when in fact the type should be "ARRAY"?
Is this a jactivex bug?

--

  ***********************************************
  Carl Clefstad, NCR Corporation
  Email: carl.clefstad@sandiegoca.ncr.com
  ***********************************************

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