?
Solved

NT 4.0/Delphi 2 c dll & record structure problem

Posted on 1997-06-21
6
Medium Priority
?
301 Views
Last Modified: 2010-04-03
Hello Delphians,

I am having a rather unique problem, that I hope someone else has run
into.  I have a 3rd party library of DLL's (completely documented
no less!) that were compiled/linked with the extern "C" prefix.  Most of these
routines take very large structures as parameters which I have been
able to covert into Delpi2/Pascal without a problem & they work fine.
All but this one & it is the smallest structure that is giving me the
most pain.


The C header defines dx_tpt as:

typedef struct dv_tpt  DV_TPT;

struct dv_tpt {
   unsigned short tp_type;      
   unsigned short tp_termno;  
   unsigned short tp_length;    
   unsigned short tp_flags;      
   unsigned short tp_data;      
   unsigned short rfu;          
   DV_TPT   *tp_nextp;          
};

This should convert fairly easily to Delphi as:

Type   pDV_TPT               = ^DV_TPT;
       DV_TPT                = record
       tp_type:                    Word;  
       tp_termno:                  Word;
       tp_length:                  Word;  
       tp_flags:                   Word;  
       tp_data:                    Word;  
       rfu:                        Word;  
       tp_nextp:                   pDV_TPT;
End;

one of the routines (this one clears the structure) is defined as:
function  dx_clrtpt(var dvtpt: DV_TPT; cnt: Integer):     Integer;
cdecl;

What happens is this: dx_clrtpt clears everything except for tp_type &
tp_nextp

If I pass the structure to a routine that is suppose to do something
more than clear it, I get an internal message saying the structure is
invalid.

The vendor is no help and told me I should write my app using C or C++
(yeah right, like I have a year to do that! :-)

I also tried setting up the structure as SmallInt's & there was no
difference.  

If anyone can think of anything I may be doing wrong...I'd sure
appreciate a nudge!!

Thanx in advance,
L
0
Comment
Question by:ls3
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
6 Comments
 
LVL 1

Expert Comment

by:ygolan
ID: 1337355
L,

Try changing the record declaration to

 DV_TPT = PACKED record


0
 

Author Comment

by:ls3
ID: 1337356
Let me add...
I have tried Packed, Alignment On & Off, using far before the cdecl and a few other silly things that made no difference.
L
0
 
LVL 1

Expert Comment

by:ygolan
ID: 1337357
Can you post the original C function definition ?

If you didn't yet, I suggest that you also write a small C program demonstrating to your self that this particular function works as expected it C, and then translate the entire program to Delphi.
0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 

Author Comment

by:ls3
ID: 1337358
At the top of my original note is the structure.

Here is the c prototype for dx_clrtpt:

extern int dx_clrtpt( DV_TPT *tptp, int size );

I have also tried defining this to Delphi using pointers too:

function dx_clrtpt(dvtpt: pDV_TPT; cnt: Integer): Integer;
cdecl;

The results were the same.  I appreciate anything else you can think of!!
L

0
 

Author Comment

by:ls3
ID: 1337359
Stop the presses...  I just wrote a little C++ program.  The bug is with my vendor as it did exactly the same thing as Delphi.  

Now how do I change this note to closed & how do I get you some points for taking the time to help me?
0
 
LVL 1

Accepted Solution

by:
ygolan earned 400 total points
ID: 1337360
I've posted this as "answer", so you can give me the points if you choose so.
0

Featured Post

Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Objective: - This article will help user in how to convert their numeric value become words. How to use 1. You can copy this code in your Unit as function 2. than you can perform your function by type this code The Code   (CODE) The Im…
In this tutorial I will show you how to use the Windows Speech API in Delphi. I will only cover basic functions such as text to speech and controlling the speed of the speech. SAPI Installation First you need to install the SAPI type library, th…
Do you want to know how to make a graph with Microsoft Access? First, create a query with the data for the chart. Then make a blank form and add a chart control. This video also shows how to change what data is displayed on the graph as well as form…
In this video, Percona Director of Solution Engineering Jon Tobin discusses the function and features of Percona Server for MongoDB. How Percona can help Percona can help you determine if Percona Server for MongoDB is the right solution for …
Suggested Courses

719 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question