What does the structure or typedef look like for the SafeArray?

Targets Windows
1

Hi Guys,

In continue with my VB6 to XOJO conversion, I encountered “COM.SafeArray” from the imported ActiveX as seen from photo below.

What is it? How can I create it?

2

I goggled it:

https://msdn.microsoft.com/en-us/magazine/mt778923.aspx

3

Hi Ronaldo,

From Karen’s helpful link, here are the two structures for SafeArray, which has one for 32-bit and another for 64-bit applications.

This is for x86 applications:

Structure tagSAFEARRAY32 cDims as UInt16 fFeatures as UInt16 cbElements as UInt32 cLocks as UInt32 pvData as Ptr _spacer as UInt32 rgsabound as Ptr End Structure

This is for x64 applications:

Structure tagSAFEARRAY64 cDims as UInt16 fFeatures as UInt16 cbElements as UInt32 cLocks as UInt32 pvData as Ptr rgsabound as Ptr End Structure

I confirmed the structures in Visual Studio C++ 2019.

4

thank you guys,

But what I need is the XOJO conversion. I believed its illegal in xojo, right?

5

The code that is shown is the Xojo code of the structure.

6

The structures are already in Xojo. I have no idea if this works and as I use COM so little, there might be a better way to do this, @William Yu probably knows.

Declare Function SafeArrayCreate Lib "OleAut32.dll" Alias "SafeArrayCreate" ( _
vt As UInt16, _
cDims As UInt32, _
ByRef rgsabound As COM.SafeArrayBound _
) As Ptr

Dim sab As COM.SafeArrayBound
sab.lbound = 0
sab.cElements = 10000 'the API says you need 10000 bytes

Dim mb As New MemoryBlock(COM.SafeArray.Size)
mb = SafeArrayCreate(17, 1, sab) '17 - bytes

Dim t As COM.SafeArray
t.StringValue(True) = mb.StringValue(0, COM.SafeArray.Size)

Declare Function SafeArrayDestroy Lib "OleAut32.dll" Alias "SafeArrayDestroy" ( _
psa As Ptr _
) As Int32

Call SafeArrayDestroy(mb)

'We can now use t here
system.DebugLog("size=" + str(t.Size))

Personally, if I were working on this project, I would change over to the DLL version of the API as I wouldn’t be constantly fighting to figure out how Xojo uses/implements COM for the ActiveX version :slight_smile:

7

I was amazed by Julian know how on this form of vb6 to xojo conversion. I believed that there is no detailed example or video demo available in the internet that show exactly what you have provided. Are you from xojo? It looks you know everything about things.

" I would change over to the DLL version of the API" - I tried the DLL before but EVENTS are not exposed. Unlike ACTIVE X, everything is exposed.

Actually, I have to use WINDOWS laptop to carry out the conversion. I wish I can do this on my macpro.

8

[quote=443579:@Eugene Dakin]Hi Ronaldo,

From Karen’s helpful link, here are the two structures for SafeArray, which has one for 32-bit and another for 64-bit applications:[/quote]

I have doubts they are correct. This is C declaration:

[code]typedef struct tagSAFEARRAY
{
USHORT cDims;
USHORT fFeatures;
ULONG cbElements;
ULONG cLocks;
PVOID pvData;
SAFEARRAYBOUND rgsabound[ 1 ];
} SAFEARRAY;

typedef struct tagSAFEARRAYBOUND
{
ULONG cElements;
LONG lLbound;
} SAFEARRAYBOUND;[/code]

So rgsabound is not a ptr, but part of the structure providing the bounds.
And the spacer may not be needed, if Xojo does aligning as C. (align structures on 8 byte boundaries for 64-bit)

9

Hi Christian,

Yes, your right, the structure looks clearer when adding the array and using the tagSAFEARRAYBOUND structure. Here is the revised code from C++ to Xojo:

Structure tagSAFEARRAY cDims as UInt16 fFeatures as UInt16 cbElements as UInt32 cLocks as UInt32 pvData as Ptr rgsabound(1) as tagSafeArrayBound End Structure

Structure tagSAFEARRAYBOUND cElements as UInt32 lBound as Int32 End Structure