Passing a string to an external DLL function in Alpha

[Rick Gerlach]

I'm using A5v8. I'm trying to call a function in an external DLL. Here's the VBA code:

Private Declare Function GetHardwareID Lib "HardwareID.dll" (ByVal bHDD As Boolean, ByVal bNIC As Boolean, ByVal bCPU As Boolean, ByVal bBIOS As Boolean, ByVal sRegCode As String) As String.

Here's what I'm doing in Alpha:

' returns string, takes 4 booleans, and a string
declare HardwareID GetHardwareID CWWWWC
' xxxx-xxxx is the registration code for removing nag window 
' you pass the registration code and it does the call silently
hdwid = GetHardwareID(0,0,1,1,"xxxx-xxxx")

I have to pass the function our registration code which unlocks the full version of the DLL.

The function call works fine, it returns the proper string, but I still get the nag screen. I have verified the registration code is good, the code works fine in VBA.

I've looked over other examples on the board and tried passing the registration code as a character variable and also as a pointer to a string:

dim temp as p
temp.sSerial = "xxxx-xxxx"
hdwid = GetHardwareID(0,0,1,1,temp)

Nothing I've tried so far has worked. According to the vendor's help file, this is how the function is declared:

LPTSTR WINAPI GetHardwareID(
BOOL bHdd,
BOOL bNic,
BOOL bCpu,
BOOL bBios,
LPCTSTR sRegCode
);

LPCTSTR is a Long Pointer Constant to a null-Terminated String. I also tried passing the serial as a Blob, no joy.

I've already emailed the vendor, but have not heard back from them yet. Is there something obvious I'm missing about passing a string to an external function?

Any help would be appreciated.

Rick

[MikeC]

Re: Passing a string to an external DLL function in Alpha

Rick,
Have you tried running a vbs script directly in Alpha with the A5_run_vbscript() built-in function instead of converting a vb script to xbasic? Or even find a vbs script and then use sys_open() to run it?

The A5_run_vbscript() function located here
http://support.alphasoftware.com/alp...VBScript().htm

[Rick Gerlach]

Re: Passing a string to an external DLL function in Alpha

Mike,

Thanks for that suggestion, I had no idea that function existed.

However, I don't think it will work for me because:
1) according to what I read, you can't call DLL's from VBScript without an ActiveX control or a wrapper and 2) I can't retrieve a value from the script other than an error code without writing the value to an intermediate file or clipboard, which is what I'm trying to avoid by using the DLL in the first place.

If you know any workarounds for those issues, I'd love to hear about them.

Thanks,
Rick

[Marcel Kollenaar]

Re: Passing a string to an external DLL function in Alpha

Hi Rick,

Try the next code:

'declare a 1 kb buffer to recieve the returned text.
declarestruct [COLOR=seagreen]udtBuffer[/COLOR] C1024[COLOR=red]varReadBuffer[/COLOR]
 
'the api function to unlock the dll
declare HardwareID GetHardwareID ([COLOR=seagreen]udtBuffer[/COLOR])WWWWC 'the wwww is correct
 
dim LPCTSTR as {[COLOR=seagreen]udtBuffer[/COLOR]}
 
LPCTSTR = GetHardwareID(0,0,1,1,"xxxx-xxxx")
 
msgbox("Title",LPCTSTR.[COLOR=red]varReadBuffer[/COLOR])

[Rick Gerlach]

Re: Passing a string to an external DLL function in Alpha

Marcel,

Thanks for that, but the return string isn't the problem, it's the "xxxx-xxxx" string that I'm trying to pass to the DLL. For some reason the DLL doesn't see it as a valid registration code, even though the code works properly in a VBA function.

I already tried passing the registration code string as a pointer to a string and it didn't work.

Any other ideas?

[Marcel Kollenaar]

Re: Passing a string to an external DLL function in Alpha

This is almost the same as:

dim temp as p
temp.sSerial = "xxxx-xxxx"
hdwid = GetHardwareID(0,0,1,1,temp)

but the declarestruct is as low level as possible.

declarestruct udtBuffer C9license
declare HardwareID GetHardwareID CWWWW(udtBuffer)
 
dim Buffer as {udtBuffer}
Buffer.license = "xxxx-xxxx"
 
hdwid = GetHardwareID(0,0,1,1,Buffer)

[Rick Gerlach]

Re: Passing a string to an external DLL function in Alpha

Marcel,

Tried the udtBuffer code, but no go. It's weird, who would think passing a string to a DLL would be such a hassle?

[Stan Mathews]

Re: Passing a string to an external DLL function in Alpha

I'm willing to show off my ignorance.

Your original post states...

LPCTSTR is a Long Pointer Constant to a null-Terminated String.

I have no idea whether normal strings in Alpha are null-Terminated or not. How about trying appending a null (chr(0)) to your "xxxx-xxxx"?

"xxxx-xxxx"+chr(0)

[Rick Gerlach]

Re: Passing a string to an external DLL function in Alpha

Yes, Alpha 5 strings are null-terminated. I did try the chr(0) idea also, just in case with both a string type and a blob type, but it didn't work.

I'm sure the answer is ridiculously simple, but the vendor is non-responsive so I'm left to blunder around trying different things. Grrr.

[Rick Gerlach]

Re: Passing a string to an external DLL function in Alpha

MARCEL IS A GENIUS!

Thanks to some private emails back and forth, Marcel put me on the right track. To make this DLL work, you declare the function as:

declare HardwareID GetHardwareID CLLLLC

I was using CWWWWC. Apparently what the DLL expects for boolean values are 32-bit signed int Longs rather than 16-bit unsigned int 'W'.

So even though the 4 boolean parameters worked, it was screwing up the string boundary of the registration code.

I had to completely reboot in order to get Marcel's example working, though, so be aware that when experimenting with declare and DLL's, it never hurts to reboot.

I just want to say thanks again to everyone who contributed suggestions to this thread and especially Marcel for coming up with the solution. That kind of generosity exemplifies why the Alpha community is one of the best.

Rick

[csda1]

Re: Passing a string to an external DLL function in Alpha

Hi Rick,

I had to completely reboot in order to get Marcel's example working, though, so be aware that when experimenting with declare and DLL's, it never hurts to reboot.

Constant rebooting of Alpha Five after changing DECLARE and DECLARESTRUCT and then restoring the development environment was the original development reason for the CSDA Code Utility for Alpha Five.

I estimated it was a minimum of 2 to 4 minutes per reboot shaved down to 30 seconds or less (plus a whole lot less typing!).

[MikeC]

Re: Passing a string to an external DLL function in Alpha

MARCEL IS A GENIUS!

No argument here! When it comes to anything regarding these dll/API conversions, Marcel sure seems to have the knack (and persistence!) in solving them.