How to use external dll and get results ?

[snmza]

I need to use external dll to communicate with digital camera and I found program with appropriate dll that enable communication.
In dll description I found function that suits my needs. Looks like this

//--------------------------------------------------------------------
// ReleaseShutter()
// Inputs:
// timeOutInSecs timeout in secs to wait for picture to be
// taken and downloaded (max 60 secs)
// pszFilename option string in which to store the name of the
// saved image. Set to NULL if not required
// numChars length of pszFilename if defined
//
// Returns:
// 0 - Success, image saved
// 1 - PSRemote is not running
// 2 - PSRemote is running but camera is not connected
// 3 - Camera is busy
// 4 - Timeout waiting for image to be saved
// 5 - Error releasing shutter
//
// Description:
// Take a picture and optionally wait for it to be saved to disk.
//
//--------------------------------------------------------------------
PSRemoteLIB_API int __stdcall ReleaseShutter(
int timeoutInSecs,
char* pszFilename,
int numChars
);

Ok, I load dll, use function an get status and external program takes a picture but
I CAN NOT GET FILENAME BACK!!!!

Here is my code

procedure TForm1.Button2Click(Sender: TObject);
var
Status: Integer;
Name1: PChar;
DLLHandle: Thandle;

TakePic: Function (T: Integer; Nam: Pchar;Num:Integer):Integer; {$IFDEF WIN32} stdcall; {$ENDIF}

begin


DLLHandle := LoadLibrary('PSRemoteLib.dll');
if DLLHandle >= 32 then { success }
begin

Name1:=stralloc(1024);
Slikaj := GetProcAddress(DLLHandle, 'ReleaseShutter');

Status:=TakePic(60,Name1,SizeOf(Name1));

edit1.Text:
label1.Caption:=intTostr(Status);
label2.Caption:=Name;

FreeLibrary(DLLHandle);
end
else
MessageDlg('Error: could not find PSRemoteLib.dll', mtError, [mbOk], 0);


StrDispose(Name1);


end;

What I do wrong ???? In the sample .exe that comes with dll and runs in cmd mode this works fine !!!! Program takes picture and report filename ????
I have a sample source code and looks like this

// take a single shot and report the filename/status
char filename[256];
int status = ReleaseShutter(60, filename, sizeof(filename));
switch(status)
{
case 0: // success
if (filename && strlen(filename))
{
cout << "Success, image saved as: " << filename << endl;
}
else
{
cout << "Success, image saved on CF card?" << endl;
}
break;

case 1:
cerr << "PSRemote is not running" << endl;
break;
case 2:
cerr << "Camera is not connected" << endl;
break;
case 3:
cerr << "Camera is busy" << endl;
break;
case 4:
cerr << "Timeout waiting for image to be saved" << endl;
break;
default:
cerr << "ERROR: unexpected return status: " << status << endl;
}
}

return nRetCode;
}



PLEASE HELP !!!

 

[Glenn9999]

 Name1: PChar;

PChar is a pointer to a character. In your code you have it pointing to nothing (as far as I can tell). See in the C sample:

 char filename[256];

It explicitly allocates 256 bytes.

Try defining as:

Name1: Array[0..255] of char;

And then code from there.

It is not possible for anyone to acknowledge truth when their salary depends on them not doing it.

 

[djjd47130]

Couldn't help but to notice 255 instead of 256... I assume this is because the index is starting from 0 in Delphi and from 1 in C?


JD Solutions

 

[Glenn9999]

in C, tables or arrays are defined by quantity and not range as in Pascal. "char filename[256]" defines 256 characters to be identified as "filename" in the code. When it comes to accessing the array/table, C is zero-based.

What I suggested is the C equivalent for the table in Delphi/Pascal.

It is not possible for anyone to acknowledge truth when their salary depends on them not doing it.

 

[sggaunt]

In 'C' arrays always index from 0.
C[256] defines an array of 256 elements 0 to 255


Steve: N.M.N.F.
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