🚀 go-pugleaf

Martin wrote:
> Hi,
> 
> I'm writing an application to test Mobitex and the MASC protocol. I've
> decided to use an dll(masc.dll). The MASC DLL is a Windows DLL that
> implements the MASC protocol, allowing applications that have no
> knowledge of MASC to communicate with Mobitex modems.
> 
> I'm using Delphi and has converted masc.h (written in C/C++) to
> delphicode. When I call a method I get the following message: 'Access
> violation att address 10001029 in module masc.dll'. Read of address
> 00000000'.
> 
> 
> This is the method I tried to call
> 
> Defintion in masc.h
> 
> EXPORT int CALLBACK MASC_Open(HMASC* hMASC, char* address,
> MASC_SETTINGS* settings, unsigned long timeout);
> 
> Definition in Delphi
> 
> function MASC_Open(hMASC :HMASC; address: PChar;
> settings:MASC_SETTINGS; Timeout: LongInt):integer; cdecl; external
> MASCDLL;
> 
> My call to MASC_Open in the code:
> 
> status := MASC_Open(hMasc, address, settings, 0);
> 
> Declaration HMASC, MASC_SETTINGS
> 
> HMASC: In masc.h typedef void* 
>        in delphi  HMASC=pointer;
> 
> MASC_SETTINGS In masc.h typedef struct 
>                         {
>                           unsigned int frameQueueSize;    
>                           unsigned int commandQueueSize;  
>                           unsigned int mpakQueueSize;     
>                           }
>              in delphi  type
>                             MASC_SETTINGS = record
> 
>                               frameQueueSize :cardinal;
>                               mpakQueueSize :cardinal;
>                              commandQueueSize :cardinal;
>                               end{MASC_SETTINGS};
> 
> I'm not very familiar with c/c++ and pointers so I wouldn't be
> surprised if the explanation to the "access violation" lies in the
> conversion of different data types and pointers.
> 
> Please help if you can, I'm stuck...
> 
> Martin
> pointers from c/c++ to delphi.
I think that you are passing the record as an argument rather than a 
pointer to the record that the dll function requires
try :-

function MASC_Open(hMASC :HMASC; address: PChar;
settings:PMASC_SETTINGS; Timeout: LongInt):integer; cdecl; external
MASCDLL;

type MASC_SETTINGS = record
  frameQueueSize :cardinal;
  mpakQueueSize :cardinal;
  commandQueueSize :cardinal;
end;
type PMASC_SETTINGS = ^MASC_SETTINGS