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 (http://htpp://www.jsv6.nl/gl2PS.zip).