HELP: Using C++ .dll in Delphi

[CRO_Tomislav 0]

Dear all.

 

Please take my apology if I post in a wrong section of this forum...

 

I new to Delphi and I have a problem with a using a C++ .dll from Delphi VCL.

In a manual for .dll I have for a next function description:

 

MXIO_GetDllVersion

Get the DLL version.

C/C++

int MXIO_GetDllVersion ();

 

Visual Basic

Declare Function MXIO_GetDllVersion Lib "MXIO.dll" () As Long

 

Arguments:

None

 

Return Value:

Succeed

Return the DLL version. If the value is 0x2000, then the version is 2.0.0.0

 

I call from Delphi this function as:

function MXIO_GetDllVersion : Integer; cdecl; external 'MXIO.dll' name 'MXIO_GetDllVersion';

 

In a ShowMessage(IntToStr(MXIO_GetDllVersion));

Problem: I get incorrect data.

Instead of 21200; I get: 11264

 

Thx in advance

Tom

[Boris Novgorodov 10]

You show decimal representation while version components correspond to nibbles of hex representation

 

  11264dec = $2C00, so your version number is 2.12.0.0  (2.$C.0.0)

Edited February 16, 2019 by Boris Novgorodov

[PeterBelow 238]

The docs you quoted state that the version is encoded in the *hexadecimal* value returned. You look at the decimal value.

Decimal 11264 is hexadecimal 0x2c00  ($2C00 in Delphi notation). So the version is 2.12.0.0

[CRO_Tomislav 0]

OMG... 

It is a long night behind me...

 

Sorry

Tom

[CRO_Tomislav 0]

I have problem with a next function. How to tranlsate it to a delphi code?

 

C/C++

int MXEIO_E1K_Connect( char * szIP,

WORD wPort,

DWORD dwTimeOut,

int * hConnection,

char * szPassword);

 

Visual Basic

Declare Function MXEIO_E1K_Connect Lib "MXIO.dll" (ByVal szIP As String, ByVal iPort As Integer, ByVal nTimeOut As Long, handle As Long, ByVal szPassword As String) As Long

 

Arguments:

szIP	IP address of the Ethernet I/O device to be connected.A-OPC Server IP address or ioLogik 1200 IP address
wPort	TCP port number of Ethernet I/O device. Please use 502 for ioLogik 1200
dwTimeOut	Timeout value for establishing a network connection with the ioLogik Ethernet Adapter. The unit is in milliseconds.
hConnection	Handle for the I/O device connection.
szPassword	Max length 8 bytes

 

Return Values :

Succeed	MXIO_OK
Fail	Refer to Return Codes.

 

I try with:

function MXEIO_E1K_Connect(szIP: String; iPort: Integer; nTimeOut: Integer; handle: Integer; szPassword: String): Integer; external 'MXIO.dll' name 'MXEIO_E1K_Connect';

 

Whene I call this function it crash my app. (Integer overflow).

Is it problem in my sintaks or error in .dll?

[uligerhardt 18]

You didn't specify a calling convention. This is probably cdecl like in MXIO_GetDllVersion. Another poular choice is stdcall.

[stijnsanders 35]

Also use PAnsiChar instead of string. It's a stricter translation of C’s *char and Delphi has great auto conversion to and from string with it

Edited February 16, 2019 by stijnsanders

[CRO_Tomislav 0]

Hi.

 

It works only with stdcall..

Cdecl chrashes...

 

With best regards

Tomislav

[Remy Lebeau 1396]

7 hours ago, uligerhardt said:

You didn't specify a calling convention. This is probably cdecl like in MXIO_GetDllVersion. Another poular choice is stdcall.

The DLL's documentation includes VB declarations.  VB doesn't support cdecl at all, only stdcall.

 

Also, I just found this, which clearly shows the DLL functions using CALLBACK for the calling convention.  That is a preprocessor macro that maps to __stdcall.

Edited February 16, 2019 by Remy Lebeau

[Remy Lebeau 1396]

8 hours ago, CRO_Tomislav said:

I have problem with a next function. How to tranlsate it to a delphi code?

...

I try with:

function MXEIO_E1K_Connect(szIP: String; iPort: Integer; nTimeOut: Integer; handle: Integer; szPassword: String): Integer; external 'MXIO.dll' name 'MXEIO_E1K_Connect';

 

Whene I call this function it crash my app. (Integer overflow).

Is it problem in my sintaks or error in .dll?

Your translation is WAY off.  DONT use String for char* parameters, use PAnsiChar instead.  DONT use Integer for (D)WORD parameters, use (D)WORD instead.  And your handle parameter needs to be declared as 'var' or 'out' since it is an output parameter.

 

Try this instead:

 

function MXEIO_E1K_Connect(szIP: PAnsiChar; wPort: WORD; dwTimeOut: DWORD; var hConnection: Integer; szPassword: PAnsiChar): Integer; stdcall; external 'MXIO.dll' name 'MXEIO_E1K_Connect';  

Or this:

function MXEIO_E1K_Connect(szIP: PAnsiChar; wPort: WORD; dwTimeOut: DWORD; hConnection: PInteger; szPassword: PAnsiChar): Integer; stdcall; external 'MXIO.dll' name 'MXEIO_E1K_Connect';

 

[CRO_Tomislav 0]

Hi.

 

It works!

 

BIG THX!!!!

 

With best regards

Tomislav

[Rudy Velthuis 91]

Befre you make more mistakes like the ones above, please ready my article about the Pitfalls of converting. It explains everything discussed here and a lot more.

Edited February 19, 2019 by Rudy Velthuis

[David Heffernan 2345]

You can tell it must be stdcall since that is the only convention supported by classic VB.