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DLL - Newbie - String passing - C DLL

Trying to use a third party dll... Here is the relevant information...  Supposed to pass it a DLL handle (I'm doing that ok...) and a pointer to a structure... (I've only shown part of the structure...)  The structure is simply a list of char's which I've converted as you can see...  The function is supposed to return dummy data in the structure, but the ShowMessage always shows 'Jason'...

Can anyone give me a pointer to getting this going?

type
  ptrAddrRec = ^AddressRecord;
  AddressRecord = Record
  Company:            Array[0..50] of Char;
  Address:            Array[0..75] of Char;
  Suite:              Array[0..16] of Char;
  City:               Array[0..28] of Char;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
AddrRec: AddressRecord;
begin
     AddrRec.Company := 'Jason';
     TestStructure(MP4Handle, @AddrRec);
     ShowMessage(String(AddrRec.Company));
end;
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loucks
Asked:
loucks
1 Solution
 
AllenCCommented:
I think you should give out more informations before anyone can help you. eg. the syntax of the TestStructure import procedure, and what does it do??

Is it like this??

procedrue TestStructure(Handle: THandle; var AddrRec: ptrAddrRec); external;

make sure you use the "var" in the import unit!

http://tcp.home.ml.org/
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loucksAuthor Commented:
Well, Now it works!  I had a var in front of MP4Handle, took that out and it returns the data correctly...  I also changed it to an untyped pointer (which I have no idea if I should or not but who cares? it works!!!)  I included the c declarations to hopefully help  someone else who might be having problems.  Thanks so much!!!!!

procedure TestStructure(MP4Handle: LongInt; AddrStr: Pointer); stdcall; external 'MP432.dll' name 'TESTSTRUCTURE';

procedure TForm1.Button1Click(Sender: TObject);
var
AddrRec: AddressRecord;
begin
     AddrRec.Company := 'Jason';
     TestStructure(MP4Handle, @AddrRec);
     ShowMessage(String(AddrRec.Company));
end;

EXTERN MP4RETVAL MP4CALLCONV TestStructure (MP4RETVAL hDllHnd, AddressRecord *);

#define COMPANY_LEN             50
#define ADDRESS_LEN             75
#define SUITE_LEN               16

#pragma pack(1)
typedef struct tagAddressRecord
{
      char company[COMPANY_LEN+1];
      char address[ADDRESS_LEN+1];
      char suite[SUITE_LEN+1];
      char city[CITY_LEN+1];
      char stdCityAbbr[STD_CITY_ABBR_LEN+1];
      char state[STATE_LEN+1];
      char zip[ZIP_LEN+1];
      char plus4[ZIP4_LEN+1];
      char cart[CART_LEN+1];
}
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