LoadLibrary

[Scott Turchin]

I'm a bit confused about LoadLibrary.
DO I still need to declare the function?

I have it working in one program (Not sure how) but my goal is to be able to run without the DLL being there(In case it gets deleted etc), detecting that and running an error function instead, is that possible?

Meanwhile, this is what I have and it does not work, I get "Missing Declaration

FreeCCSDLL = "FREECCSDLL" 'Global

Function ProcessCreditCards() As Long
Local x As Long
Local hLib As Long
Local procAddr As Long
Local Param As Asciiz * 255

hLib = LoadLibrary("FREECCS.DLL")
If IsFalse hLib Then
MsgBox FreeCCSDLL + " is missing or damaged, please verify installation", %MB_ICONSTOP,CCS
Exit Function
End If
procAddr = GetProcAddress(hLib, FreeCCSDLL) 'Function Name is "FreeCCSDLL"
Result = @FreeCCSDLL("Setup", "ATZ")'
'etc etc

-------------
Scott Turchin

[Fred Oxenby]

procAddr = GetProcAddress(hLib, FreeCCSDLL) 'Function Name is "FreeCCSDLL"

1) FreeCCSDLL must be a null-terminated string
2) The spelling and case of the function name must be identical
to that in the EXPORTS statement of the source DLL.
That is: have you declared Alias "FreeCCSDLL"



-------------
Fred
mailto:[email protected][email protected]</A>
http://www.oxenby.se

[Scott Turchin]

Here's what I have for the declare and what the author put for his:

Declare Function FreeCCSDLL Lib "FREECCS.DLL"(Key As Asciiz, Param As Asciiz) As Long
'-------------------------------------------------
long FreeCCSDLL(char *key, char *param) // exports index 1
//"key" and "param" are pointers to zero-terminated strings.
//If the call is successful, the function returns zero, otherwise
//the function returns one of the following error codes:
'-------------------------------------------------

So I put the declare back in and getting the message:
"Function referenced before declaration"


Ideas why?

-------------
Scott Turchin




[This message has been edited by Scott Turchin (edited January 14, 2000).]

[Fred Oxenby]

FreeCCSDLL = "FREECCSDLL" 'Global

Declare Function FreeCCSDLL Lib "FREECCS.DLL"(Key As Asciiz, Param As Asciiz) As Long

This two function-names are NOT Equal.
Your function-name is FreeCCSDLL
You tries to get address of FREECCSDLL
If you declare the functions in FREECCS.DLL you will explicit load
the DLL at program-start
This is not what you want. If the file is missing, you want to
detect that and take some action.



-------------
Fred
mailto:[email protected][email protected]</A>
http://www.oxenby.se

[Scott Turchin]

FreeCCSDLL = "FreeCCSDLL"

Tried that too, didn't matter.

Basically, I want the program to be able to start whether or not the file is there, is that possible? If so, how?



-------------
Scott Turchin

[Lance Edmonds]

Scott, drop the LIB "dllname.dll" from the declaration, then proceed as you were... once you get the address of the function with GetProcAddress(), use CALL DWORD...USING... TO to call the function in the dynamically loaded DLL.



-------------
Lance
PowerBASIC Support
( mailto:[email protected][email protected]</A> )

[Scott Turchin]

Thanks!
I also had a string by the same name as the function, DOH!

So far so good!

Here's what I have and the error message I'm getting:

Declare Function FreeCCSDLL(Key As Asciiz, Param As Asciiz) As Long

Function ProcessCreditCards() As Long
Local x         As Long
Local hLib      As Long
Local procAddr  As Long
Local Param     As Asciiz * 255

hLib = LoadLibrary("FREECCS.DLL")
If IsFalse hLib Then
   MsgBox "FreeCCS.DLL is missing or damaged, please verify installation", %MB_ICONSTOP,CCS
   Exit Function
End If
procAddr = GetProcAddress(hLib,"FreeCCSDLL") 'Function Name is "FreeCCSDLL"
Call Dword Using @FreeCCSDLL("Setup", "ATZ") To Result

Should I be declaring the function DWORD?

-------------
Scott Turchin




[This message has been edited by Scott Turchin (edited January 15, 2000).]

[E B Knoppert]

Be sure you free it using FreeLibrary!

Note: After this, the CALL DWORD is not valid anymore..

[Scott Turchin]

Yup!
But,
I'm still getting a "Variable expected"
Here's what I have entirely so far, it's still raw..

'------------------------------------------------------------------------------
Function ProcessCreditCards() As Long
Local x         As Long
Local hLib      As Long
Local procAddr  As Long
Local Param     As Asciiz * 255

hLib = LoadLibrary("FREECCS.DLL")
If IsFalse hLib Then
   MsgBox "FreeCCS.DLL is missing or damaged, please verify installation", %MB_ICONSTOP,CCS
   Exit Function
End If
procAddr = GetProcAddress(hLib,"FreeCCSDLL") 'Function Name is "FreeCCSDLL"

For x = 1 To wCount

   VARIABLE EXPECTED ERROR:

    Call Dword Using @FreeCCSDLL("Setup", "ATZ") To Result

    'Result = @FREECCSDLL("Port","COM" + Comport)

    'Call Dword Using @FreeCCSDLL("Port", "COM" + ComPort) To Result


    'Call FreeCCSDLL("Phone", "")'
    'Call FreeCCSDLL("SetupTime", "5000")' // 5 seconds FOR Timeouts
    'Call FreeCCSDLL("SubmitTime", "30000")' // 30 seconds wait for CONNECT
    '
    'Call FreeCCSDLL("CreditCard", "1234123412341234")' // numerics only!
    'Call FreeCCSDLL("Expires", "0899")' // August 1999
    'Call FreeCCSDLL("Amount", "123")' // numerics only! ($1.23)
    'Call FreeCCSDLL("Action", "Sell")' // Not Refund/Get/Post/etc.
    'Call FreeCCSDLL("Terminal", "HC12345654321")'
    'Call FreeCCSDLL("Port", "COM2")'
    'Call FreeCCSDLL("Phone", "1-800-555-1212")'
    'Call FreeCCSDLL("Submit", Param)'
    
    'Return returns the following:
    'CAPTURE <approval number appears here>
    'SALE <amount appears here>
    'REF NO <transaction number appears here>
    'BAL <the day's transaction balance appears here> <the transaction "batch" number appears here>
Next

Result = FreeLibrary(hLib)

End Function

-------------
Scott Turchin




[This message has been edited by Scott Turchin (edited January 15, 2000).]

[Florent Heyworth]

Hi Scott

you are not going about this the right way - the compiler is moaning because you are telling it that the function you want to call is contained within a pointer variable called FreeCCSDLL - besides ProcAddr should be a DWORD! This is how you should go about it (you're almost there):

'Declare function prototype
Declare Function protoFreeCCSDLL (Key as ASCIIZ,Param as ASCIIZ) as LONG

Function ProcessCreditCards() as LONG
    Local x as LONG
    Local hLib as LONG
    Local ProcAddr as DWORD
    local lResult as LONG

    'Retrieve DLL handle
    hLib = LoadLibrary("FREECCS.DLL")
    If IsFalse hLib Then
        MsgBox "FreeCCS.DLL is missing or damaged, please verify installation", %MB_ICONSTOP,"CCS"
        Exit Function
    End If

    'Retrieve function address
    ProcAddr = GetProcAddress(hLib,"FreeCCSDLL")
    If ProcAddr = %NULL Then
        MsgBox "Could not find function FreeCCSDLL in FreeCCS.DLL"
        Exit Function
    End If
 
    Key = "MyKey"
    Param = "MyParam"

    'Call pointer to the function using Function prototype
    Call DWORD ProcAddr USING protoFreeCCSDLL(Key,Param) TO lResult
    
    'Do some more calls/processing

    'Release Library
    Call FreeLibrary(hLib)

    Function = lResult
End Function

Cheers

Florent


[This message has been edited by Florent Heyworth (edited January 15, 2000).]

[Scott Turchin]

Very nice!
That compiles nicely.
I'm not certain on the "prototype" thing though, is that a requirement or is that just a sample of the function?

Scott

-------------
Scott Turchin

[Florent Heyworth]

Hi Scott

the function declaration, it could be a sub, which I called the prototype is necessary when you want to call a function pointer (as in CALL DWORD) and pass it variables to act on. You can think of the prototype as a function signature: if you have a function you want to call using CALL DWORD then you need to declare what type of variables, as well as BYVAL or BYREF, the function accepts - if the funtion does not accept any variables then you can just get away with CALL DWORD ProcAddr. That way the compiler knows what it should pop on the stack, whether to expect a return value, etc...

Obtaining a CODEPTR in your own BAS module is actually no different to using the LoadLibrary,GetProcAddress calls. It's just a shortcut which you can use in your own modules (not external ones).

Look up CALL DWORD in the PB help file for additional information.

Cheers

Florent

[Scott Turchin]

Awesome, thanks!

And the code works beautifully, I deleted the DLL and tested and it came up and said "Verify installation", great!!

Scott

-------------
Scott Turchin

[Scott Turchin]

I went back into my Winlog program to do this thing properly as well but met up wiht a pointer error, can you explain this?

Global procAddr     As Dword
Global hLib         As Long
'CreateShortCut
Declare Function protoCreateShortcut Alias "CREATESHORTCUT"_
                 (sPath As String, _               ' Path of the file the shortcut refers too.
                  sArguments As String, _          ' Program command line args.
                  sLocation As String, _           ' Destination path for the shortcut.
                  sWorkingDir As String, _         ' Working directory.
                  ByVal nCmdShow As Long) As Long  ' Initial window state of program.   

                  hLib = LoadLibrary("SHORTCUT.DLL")
                  If hLib Then
                      procAddr = GetProcAddress(hLib, "CreateShortcut")
                      If ProcAddr = %NULL Then
                           MsgBox "Could not find function ""CreateShortcut"" in SHORTCUT.DLL",%MB_ICONSTOP,CCS
                           Exit Function
                      Else
                          Call Dword ProcAddr Using protoCreateShortCut(_
                          FilePath + WinLogEXE,"", sLocation, FilePath,2)' To Result  'Com port to use
                          Result = FreeLibrary(hLib)
                      End If

                  Else
                      MsgBox "Unable to open DLL, file may be corrupt or missing",48, Mine
                  End If

-------------
Scott Turchin

[Lance Edmonds]

Can you be more precise about your pointer error? Is it a compile-time or run-time error?

-------------
Lance
PowerBASIC Support
( mailto:[email protected][email protected]</A> )

[Scott Turchin]

Righht after I posted this the compiler error went away. It compiles, and then tells me it can't find the DLL...Think I can handle that piece of it
I'll probably take a closer look at it today...
THanks
Scott

-------------
Scott Turchin