How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Hi All,
I've been trying for the past few hours to call IEnumVARIANT::Next() on a collection Enum. I would like this as I am building a wrapper for EnumVARIANTs giving them more possibilities.
Code:
'Example - Ideally i'd like to use more than just a Collection object
Dim col as Collection
set col = new Collection
Dim e as IEnumVARIANT
set e = col.[_NewEnum]
Do While true
Dim x as variant
CopyVariant x , vbEnumNext(e)
if isNull(x) then Exit Do
'...
Loop
Every time I try to do this however I get a crash... :confused: I'm clearly doing something wrong...
Code:
Private Declare PtrSafe Function EnumCall Lib "oleaut32.dll" Alias "DispCallFunc" (ByRef pObject As IEnumVARIANT, ByVal offsetinVft As Long, ByVal CallConv As Long, ByVal retTYP As Integer, ByVal paCNT As Long, ByRef pTypes() As Long, ByRef pValues() As Long, ByRef retVar As Variant) As Long
Private Enum CALLRETURNTUYPE_ENUM
CR_None = vbEmpty
CR_LONG = vbLong
CR_BYTE = vbByte
CR_INTEGER = vbInteger
CR_SINGLE = vbSingle
CR_DOUBLE = vbDouble
CR_CURRENCY = vbCurrency
' if the value you need isn't in above list, you can pass the value manually to the
' CallFunction_DLL method below. For additional values, see:
' http://msdn.microsoft.com/en-us/library/cc237865.aspx
End Enum
Const CC_STDCALL As Long = 4&
Public Function vbEnumNext(ByRef e As IEnumVARIANT) as Variant
Dim paTypes() As Long
ReDim paTypes(1 To 3)
paTypes(1) = CR_INTEGER
paTypes(2) = CR_LONG
paTypes(3) = CR_LONG
Dim p1 As Long: p1 = 1
Dim p2 As Variant
Dim p3 As Long
Dim paValues(1 To 3) As Long
paValues(1) = VarPtr(p1)
paValues(2) = VarPtr(p2)
paValues(3) = VarPtr(p3)
Dim hResult As Long, retVar As Variant
hResult = EnumCall(e, 4, CC_STDCALL, CALLRETURNTUYPE_ENUM.CR_LONG, 3, paValues, paTypes, retVar)
Call CopyVariant(vbEnumNext, retVar)
End Function
Public Sub CopyVariant(ByRef dest As Variant, ByVal src As Variant)
If IsObject(src) Or VarType(src) = 13 Then
Set dest = src
Else
dest = src
End If
End Sub
I've had numerous issues from compile errors to straight up crashes... I've also searched this forum and was surprised that I didn't actually find this being done before... I've seen 1 post by fafalone where oleexp3.IEnumVARIANT was used, but I want to avoid the need for external type libraries. I've also tried using passing in ObjPtr(e) as the first argument, however it appears ObjPtr doesn't support a parameter of type IEnumVARIANT (which I find a little odd given that IEnumVARIANT does implement IUnknown...)
Has anyone got any ideas of where I'm going wrong / have an example?
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Quote:
Originally Posted by
Eduardo-
May I ask why you need this instead of just doing a For/Next?
You may :) It's for a class I am working on which wraps enumerable "things". Currently I only offer a wrapper around IEnumVARIANT i.e.
Code:
For each x in pObject
'...
Next
However I want to be able to initialise the object from different sources other than a Object, e.g. An array, or a callback function. I want to be able to use:
Code:
Do While true
Dim x as variant
select case iMode
case eEnumVARIANT
CopyVariant x , vbEnumNext(e)
case eArray
index = index + 1
CopyVariant x, loopArray(index)
case eCallback
CopyVariant x, oCallback(lastValue)
end select
if isNull(x) then Exit Do
'...
Loop
With this ability I'll be able to treat callbacks like Fibonacci(val) as enumerators :D Currently the only alternative I have is to replicate the entire sub loop with all the code:
Code:
Public Function ForEach(Optional ByVal cb As stdICallable, Optional ByVal WithIndex as boolean = false) As stdEnumerator
select case iMode
case EnumeratorType.FromCallable
Dim x as variant
Do While True
Call CopyVariant(x,root.Run(x))
if isNull(x) then Exit Do
i=i+1
if withIndex then
Call cb.run(i,v)
else
Call cb.run(v)
end if
Loop
case EnumeratorType.FromIEnumVariant
Dim v as variant, i as long: i=0
For Each v In pEnumObject
i=i+1
if withIndex then
Call cb.Run(i,v)
else
Call cb.Run(v)
end if
Next
End Select
set ForEach = me
End Function
Given that my class has 30 methods I don't really want to copy and paste code all over the place (maintainability would be rubbish).
Generally speaking the long term goal of what I am doing will look something like this:
Code:
Call stdEnumerator.CreateFromCallable(fibonacci,0).map(stdLambda.Create("$1*10")).filter(stdLambda.Create("$1<=20")).forEach(debugPrint)
Call stdEnumerator.CreateFromEnumVARIANT(oCol).map(stdLambda.Create("$1*10")).filter(stdLambda.Create("$1<=20")).forEach(debugPrint)
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
OK, thank you for the explanation.
I had deleted my message because after I posted it I re-read your OP more caresfully and saw:
Quote:
I would like this as I am building a wrapper for EnumVARIANTs giving them more possibilities.
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
This is likely one reason why you are crashing...
Code:
hResult = EnumCall(e, 4, ...)
4 cannot be correct. Since IEnumVARIANT inherits from IUnknown, then the 1st 3 entries of IEnumVARIANT vTable are QueryInterface, AddRef & Release. The value 4 would be AddRef. The IEnumVARIANT:Next would be 16 not 4 (if you were trying to call the that method). I didn't verify the method order in IEnumVARIANT, it looks like ?...
-- IUnknown:QueryInterface
-- IUnknown:AddRef
-- IUnknown:Release
-- IEnumVARIANT:Clone
-- IEnumVARIANT:Next
-- IEnumVARIANT:Reset
-- IEnumVARIANT:Skip
double check these against oleexp3.IEnumVARIANT maybe.
Honestly, I stopped examining your code after I saw that initial error.
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Quote:
Originally Posted by
LaVolpe
This is likely one reason why you are crashing...
Code:
hResult = EnumCall(e, 4, ...)
4 cannot be correct. Since IEnumVARIANT inherits from IUnknown, then the 1st 3 entries of IEnumVARIANT vTable are QueryInterface, AddRef & Release. The value 4 would be AddRef. The IEnumVARIANT:Next would be 16 not 4 (if you were trying to call the that method). I didn't verify the method order in IEnumVARIANT, it looks like ?...
-- IUnknown:QueryInterface
-- IUnknown:AddRef
-- IUnknown:Release
-- IEnumVARIANT:Clone
-- IEnumVARIANT:Next
-- IEnumVARIANT:Reset
-- IEnumVARIANT:Skip
double check these against oleexp3.IEnumVARIANT maybe.
Honestly, I stopped examining your code after I saw that initial error.
Waiiit... The value is multiplied by 4?! Woops... That's the ptr size right?
I used the vtable order from here: https://sourcegraph.com/github.com/g...enumvariant.go
I have no clue how to get the real vtable order to be honest, other than from looking at other existing source code...
Edit: Mhm I see now, so given this is the vtable order:
Code:
type IEnumVARIANTVtbl struct {
IUnknownVtbl
Next uintptr
Skip uintptr
Reset uintptr
Clone uintptr
}
The method is at position 4 correct so to translate this to the VTable location I guess each pointer is 4 bytes long, so we do (4-1)*4 as the vTable offset?
Edit: I've changed that and I'm still getting all the crashes sadly... Damn I wish it errored and didn't just crash on me...
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
FYI you can use __vbaForEachCollVar and __vbaNextEachCollVar functions as well.
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Quote:
Originally Posted by
The trick
FYI you can use __vbaForEachCollVar and __vbaNextEachCollVar functions as well.
I had wondered about that, but do you know the declaration specification?
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
So in the end I didn't really come up with a proper solution but I did come up with a solution which is ridiculously ugly but works for what I needed... :lol:
Behold, the behemoth:
Code:
Sub t()
Dim c As Collection
Set c = New Collection
c.Add "a"
c.Add "b"
c.Add "c"
Do While True
Dim iterated As Variant
Select Case iMode
Case 1
Dim initialised As Boolean
If Not initialised Then
GoSub InitIEnumVARIANT
Else
GoSub NextItem
End If
Case 2
'...
Case 3
'...
End Select
if isNull(iterated) then Exit Sub
'Rest of the loop
Loop
Exit Sub
InitIEnumVARIANT:
initialised = True
For Each iterated In c
Return
NextItem:
Next
iterated = Null
Return
End Sub
Note: I'm pretty surprised this actually worked to be honest...
I did try to segregate the code to a function:
Code:
Private Function vbNext(Optional ByVal oCaller As Object = Nothing) As Variant
If oCaller Is Nothing Then GoTo GoTo1
Static pCaller As Object: Set pCaller = oCaller
Static x As Variant
For Each x In pCaller
Call CopyVariant(vbNext, x)
GoTo GoTo2
GoTo1:
Next
vbNext = Null
GoTo2:
End Function
I thought this would work, but turns out the for-each progress gets lost when leaving the function, which to be fair isn't too surprising. The whole stack gets popped after all...
Anyway, that's my filthy function. In fairness it has it's benefits, it's cross-platform compatable, and lack of dlls is good sometimes I guess... Thanks all for the help and ideas :)
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Code:
Option Explicit
Private Const CC_STDCALL As Long = 4
Private Declare Function DispCallFunc Lib "oleaut32.dll" ( _
ByRef pvInstance As Any, _
ByVal oVft As Long, _
ByVal cc As Long, _
ByVal vtReturn As VbVarType, _
ByVal cActuals As Long, _
ByRef prgvt As Any, _
ByRef prgpvarg As Any, _
ByRef pvargResult As Variant) As Long
Private Sub Form_Load()
Dim cCol As Collection
Dim cEnum As IUnknown
Dim vItem As Variant
Dim lFetched As Long
Set cCol = New Collection
cCol.Add 4
cCol.Add 3
cCol.Add 2
cCol.Add 1
Set cEnum = cCol.[_NewEnum]
Do While IEnumVariant_Next(cEnum, 1, vItem, lFetched) = 0
Debug.Print vItem
vItem = Empty
Loop
End Sub
Private Function IEnumVariant_Next( _
ByVal cEnum As IUnknown, _
ByVal celt As Long, _
ByRef rgVar As Variant, _
ByRef pCeltFetched As Long) As Long
Dim iTypes(2) As Integer
Dim pArgs(2) As Long
Dim vArgs(2) As Variant
Dim hr As Long
Dim vRet As Variant
vArgs(0) = celt: vArgs(1) = VarPtr(rgVar): vArgs(2) = VarPtr(pCeltFetched)
iTypes(0) = vbLong: iTypes(1) = vbObject: iTypes(2) = vbObject ' // vbObject - pointer type
pArgs(0) = VarPtr(vArgs(0)): pArgs(1) = VarPtr(vArgs(1)): pArgs(2) = VarPtr(vArgs(2))
hr = DispCallFunc(ByVal ObjPtr(cEnum), &HC, CC_STDCALL, vbLong, 3, iTypes(0), pArgs(0), vRet)
If hr < 0 Then
Err.Raise hr
End If
IEnumVariant_Next = vRet
End Function
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Code:
Option Explicit
Private Declare Function vbaForEachCollVar Lib "msvbvm60" Alias "__vbaForEachCollVar" ( _
ByRef cEnum As IUnknown, _
ByRef vItem As Variant, _
ByVal cColl As Object) As Long
Private Declare Function vbaNextEachCollVar Lib "msvbvm60" Alias "__vbaNextEachCollVar" ( _
ByRef cEnum As IUnknown, _
ByRef vItem As Variant) As Long
Private Sub Form_Load()
Dim cCol As Collection
Dim vItem As Variant
Dim cEnum As IUnknown
Set cCol = New Collection
cCol.Add 4
cCol.Add 3
cCol.Add 2
cCol.Add 1
If vbaForEachCollVar(cEnum, vItem, cCol) Then
Do
Debug.Print vItem
Loop While vbaNextEachCollVar(cEnum, vItem)
End If
End Sub
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Wow, this is too good not to mix both like this
Code:
Option Explicit
Private Declare Function vbaNextEachCollVar Lib "msvbvm60" Alias "__vbaNextEachCollVar" ( _
ByRef pEnum As IUnknown, _
ByRef vItem As Variant) As Long
Private Sub Form_Load()
Dim cCol As Collection
Dim vItem As Variant
Dim pEnum As IUnknown
Set cCol = New Collection
cCol.Add 4
cCol.Add 3
cCol.Add 2
cCol.Add 1
Set pEnum = cCol.[_NewEnum]
Do While vbaNextEachCollVar(pEnum, vItem)
Debug.Print vItem
Loop
End Sub
cheers,
</wqw>
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
wqweto, not all the interfaces has the accessible _NewEnum property. For example an array of controls or scrrun.Dictionary.
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Sure!
__vbaForEachCollVar obviously does the heavy-lifting of calling DISPID_NEWENUM on the IDispatch to return the IEnumVARIANT. No one asked it to call Next too on this interface though (but probably the compiler designers had they reasons)
cheers,
</wqw>
Re: How to call IEnumVARIANT::Next() with DispCallFunc() - Without external TLBs
Quote:
Originally Posted by
The trick
Code:
Option Explicit
Private Declare Function vbaForEachCollVar Lib "msvbvm60" Alias "__vbaForEachCollVar" ( _
ByRef cEnum As IUnknown, _
ByRef vItem As Variant, _
ByVal cColl As Object) As Long
Private Declare Function vbaNextEachCollVar Lib "msvbvm60" Alias "__vbaNextEachCollVar" ( _
ByRef cEnum As IUnknown, _
ByRef vItem As Variant) As Long
Private Sub Form_Load()
Dim cCol As Collection
Dim vItem As Variant
Dim cEnum As IUnknown
Set cCol = New Collection
cCol.Add 4
cCol.Add 3
cCol.Add 2
cCol.Add 1
If vbaForEachCollVar(cEnum, vItem, cCol) Then
Do
Debug.Print vItem
Loop While vbaNextEachCollVar(cEnum, vItem)
End If
End Sub
Wowee! Now I'm gutted I can't seem to use these APIs in VBA... They seem to be weirdly embedded in the VBE7.dll but not accessible... And for whatever reason that means I can't import them from msvbvm60 also... :mad: Perhaps they are actually accessible via Ordinal, I did start decompiling VBE7.dll to see if I could find the offset but didn't manage in the end... Thanks also for completing the DispCallFunc approach though! Mega helpful and actually clean too! I think I'll end up sticking with that approach for now :)
