Convert C header to Pascal (to use dll in project)

[WhatJac3]

Hello,

I am trying to convert a C header file to Pascal to use the dll (gl2ps) in my application. I have a 3 little problems with it. Maybe any of you can help me with this.

The C header file is:

typedef GLfloat GL2PSrgba[4];

GL2PSDLL_API GLint gl2psBeginPage(const char *title, const char *producer, 
                 GLint viewport[4], GLint format, GLint sort,
                 GLint options, GLint colormode,
                 GLint colorsize, GL2PSrgba *colormap, 
                 GLint nr, GLint ng, GLint nb, GLint buffersize,
                 FILE *stream, const char *filename);

My current conversion is:

GL2PSrgba = array[0..3] of GLfloat;

function gl2PSBeginPage(const title: PAnsiChar; const producer: PAnsiChar;
            GLint viewport[4];                 // <--- PROBLEM 1
            format,sort,options,colormode,colorsize: GLInt;
            GL2PSrgba *colormap;                // <--- PROBLEM 2
            nr, ng, nb, buffersize: GLInt;
            FILE *stream;                   // <--- PROBLEM 3
            const filename: PAnsiChar): GLInt;
            stdcall; external 'gl2ps.dll';

My 3 problems are:

1) How to pass an array[4] of type GLInt?
2) How to pass *var as GL2PSrgba?
3) What is a compareable type in Pascal with FILE?

[jdarling]

PGL2PSrgba = ^GL2PSrgba;

function gl2PSBeginPage(const title: PAnsiChar; const producer: PAnsiChar;
            viewport: array[0..3] of GLint;                 //array of 4 glint elements
            format,sort,options,colormode,colorsize: GLInt;
            colormap : PGL2PSrgba;                // pointer to colormap information
            nr, ng, nb, buffersize: GLInt;
            stream : TStream;                   // this may be wrong, but should be a file stream pointer
            const filename: PAnsiChar): GLInt;
            stdcall; external 'gl2ps.dll';

[WhatJac3]

If I change the

viewport: array[0..3] of GLint;

into

 
GLVWarray = array[0..3] of GLInt;

viewport: GLVWarray;

the compiler accepts it. Now let me check whether it works. Thanks so far, I'll get back to you.

[WhatJac3]

The program completely crashes if I put any code anywhere which calls any of the dll functions.

Let's take a more easier function first. I have converted:

GL2PSDLL_API GLint gl2psEndPage(void);

into

function gl2psEndPage(): GLInt; stdcall; external 'gl2ps.dll';

Now if I add the code:

var
 state: GLInt;
begin
 state := gl2psEndPage();

The application completely crashed before even showing any of the information. Compiling works but executing gives me an error and won't start, until I comment those lines.

Here is what the compiler says:

Module Load: COMDLG32.dll. No Debug Info. Base Address: $75E30000. Process General.exe (3976)
Module Load: UNKNOWN_MODULE_11. No Debug Info. Base Address: $67660000. Process General.exe (3976)
Module Load: MSVCR100D.dll. No Debug Info. Base Address: $5F4D0000. Process General.exe (3976)
Debug Output: *** A stack buffer overrun occurred in "C:\...\General.exe" : Process General.exe (3976)
Debug Output: This is usually the result of a memory copy to a local buffer or structure where the size is not properly calculated/checked. Process General.exe (3976)
Debug Output: If this bug ends up in the shipping product, it could be a severe security hole. Process General.exe (3976)
Debug Output: The stack trace should show the guilty function (the function directly above __report_gsfailure). Process General.exe (3976)
Debug Output: *** enter .exr 770B9310 for the exception record Process General.exe (3976)
Debug Output: *** then kb to get the faulting stack Process General.exe (3976)

[WhatJac3]

I found out with DLL export viewer that I might not have the correct DLL, since it does not export any functions. I'll check into that first

[paul_nicholls]

Hi WhatJac3,
Perhaps you also have an incorrect calling convention defined?

Maybe

function gl2psEndPage(): GLInt; stdcall; external 'gl2ps.dll';

should be?

function gl2psEndPage(): GLInt; cdecl; external 'gl2ps.dll';

hmm...if the DLL doesn't export any routines, the code wouldn't compile, would it?

cheers,
Paul

[WhatJac3]

I have recompiled the dll and changed all sorts of things and now it does show the export functions.

After this I got errors again and I changed the calling convention and now I dont get any errors. Now keep my fingers crossed to see if it really works.

[WhatJac3]

Now it does not accepts the GL2PSBeginPage function. If I let that one in, it just crashes. This is my current code:

type
 GL2PSrgba = array[0..3] of GLfloat;
 GLVWarray = array[0..3] of GLInt;

 PGL2PSrgba = ^GL2PSrgba;

function gl2PSBeginPage(const title: PAnsiChar; const producer: PAnsiChar;
            viewport: GLVWarray;
            format,sort,options,colormode,colorsize: GLInt;
            colormap: PGL2PSrgba;
            nr, ng, nb, buffersize: GLInt;
            stream: TStream;
            const filename: PAnsiChar): GLInt;
            cdecl; external 'gl2ps.dll';

This is how I call the code:

  
 const cExportTitle = 'test';
 const cExportCreator = 'test';

var
 buffsize, state: GLInt;
 viewport: GLVWarray;
 fp: TFileStream;
 FileName : PAnsiChar;
begin

 FileName := PAnsiChar(Name);
 fp := TFileStream.Create(Name, fmOpenWrite or fmCreate);
 buffsize := 0;
 state := GL2PS_OVERFLOW;

 glGetIntegerv(GL_VIEWPORT, @viewport);

gl2psBeginPage (cExportTitle, cExportCreator, viewport,
           GL2PS_EPS, GL2PS_NO_SORT, GL2PS_SILENT OR
           GL2PS_SIMPLE_LINE_OFFSET OR GL2PS_OCCLUSION_CULL OR
           GL2PS_BEST_ROOT,
           GL_RGBA, 0, nil, 0, 0, 0, buffsize,
           fp, FileName);

The dll and the unit that I created can be found at htpp://www.jsv6.nl/gl2PS.zip.