Getting memory address out of c into bmax

BlitzMax Forums/BlitzMax Programming/Getting memory address out of c into bmax

col	(Posted 2005) [#1]

Hi all.

How would I get go about getting the memory address of, say a texture, in a c program and use the same memory address in my bmax program? Or to put it another way I want to be able to know the address of a texture in both my bmax proggy and my c proggy, and be able to pass the address from c into bmax then back into c.

[EDIT]Blimey that isn't very clear is it??? Do you understand what I mean?

Cheers

mouss38

(Posted 2005) [#2]

I see what you mean. I'm working on a MD2Loader c Module but dont know how to access the memory address of my C class from BMAX without having a billion params in my extends function ...

regards

Dreamora

(Posted 2005) [#3]

varptr is the same as a pointer in c ( of the specific type of the var following it )

so to call a c function you use varptr and vice versa

col	(Posted 2005) [#4]

Like this :-

In BMaxgl.c

int texture=90;

//test function
long ptrGetTexture()
{
	return &texture;
}

In my gl.mod folder use:-

Import "BMaxGL.c"

Extern
	Function ptrGetTexture:Int()
EndExtern

Function glGetTexturePTR:Int()
	Return ptrGetTexture()
End Function

Then I create program file to get the address of the texture I use :-

Import nrg.gl

Print glGetTexturePTR()

This seems to give me the address. Is this what you mean??

Thanks

Dreamora

(Posted 2005) [#5]

your function does not return an int but a int ptr ( or I think more a byte ptr than int ptr )

if you try to access to it as int it should give you an error.

col	(Posted 2005) [#6]

@Dreamora
It is infact returning the correct address of the 'texture variable' as a integer value. Thanks, coz you made me remember there are variable pointers built into blitz :)

@mouss38
Are you trying to access structures from a c program but within bmax? If so, then I just solved that problem ( well, one way - from c into bmax at the mo ) :p

c program:

typedef struct 
{
	int x;
	int y;
} test;


test t;

//test function
long GetPointer()
{	
	t.x=10;
	t.y=20;

	return &t;
}

.mod program:

Extern
	Function GetPointer:Int Ptr()
EndExtern

Function GetMemPtr:Int Ptr()
	Return GetPointer()
End Function

.bmax program:

Local test:Int Ptr
test = getmemptr()

Print test[0]

test:+1

Print test[0]

'or you could use:-
test = getmemptr()
Print test[0]
Print test[1]

Does this help?
[EDITED} Strange..... for some reason a c++ version of the program gives an 'undefined reference to `GetPointer' ' error.
[EDITED ADGAIN] OK, So I've learned that the calling conventoin in c++ needs the 'extern 'c' ' command around your function prototypes. Learning more and more everyday.....