Newsgroups: comp.os.msdos.djgpp
From: Twan Jans-Beken <jabe AT oce DOT nl>
Subject: Re: Assembly routines with C++
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Date: Thu, 29 Jul 1999 11:19:57 GMT
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

I am not shure that I understand exactly what your problem is, but I
gues that you mean that main.c and gui.c want to call line WITHOUT the
last parameter.
In that case a solution is simple...

--- 8< FIRST SOLUTION >8 ---
Suppose you have a class SCREEN:
class SCREEN {
   private:
      BUFFERTYPE buffer;
      ...
   public:
      void line(int x1, int y1, int x2, int y2, void *back = &buffer);
      ...
   }

In this manner you can call line with 4 and 5 parameters. From gui.c and
main.c you can call line with only 4 parameters. They can call line also
with 5 parameters but then they must define their own buffer.

--- 8< SECOND SOLUTION >8 ---
Suppose you have a class SCREEN:
class SCREEN {
   private:
      BUFFERTYPE buffer;
      void private_line(int x1, int y1, int x2, int y2, void *back =
&buffer);
      ...
   public:
      void line(int x1, int y1, int x2, int y2) {
         private_line(x1,y1,x2,y2,&buffer);
         }
      ...
   }

In this manner you make only the four-parameter version available to the
other classes. The five-parameter version is only available to the
SCREEN class.

Note: I have never tested my solutions, so they may need some expert
review.



Mohamed Saad wrote:

> Hi All,
>    How are u? hope all is ok! ;)
>
>    well... i am currently switching from C to C++! I
> have a C program that i want to transform into
> object-oriented approach! but i have one simple (I
> hope! :)) question!
>
>    I had an .asm file compiled and linked with my
> program! This file contained a function called
> line()... here is its prototype...
>
> void line(int x1,int y1,int x2,int y2,char color,void*
> back);
>
> well... back is the back buffer.... and it is global!
>
> line() was called from several other parts in my
> program... (e.g. in gui.c and in main.c!)
>
> well... now, to make it into object oriented, the
> function line should be a member of the Class called
> 'screen'! the back buffer also should be a member of
> the 'screen' Class...
>
> So... where is the problem?
> well... other objects (e.g. gui) should NOT have
> access to the backbuffer data structure! OOP
> principles are clear! Classes should never export data
> structures! it should export a method to modify this
> data structure...
> so... back will be hidden from other classes!! they
> will not be able to call line()!
>
> so... is there a way so that i can make the .asm file
> *see* the member back of the Class called 'screen'? so
> that it can modify it?  line() is a member of the
> class... but, how can i persuade the *assembler* (NASM
> btw!!)...
>
> Any suggestions are welcome! Thanx in advance!
>
> URS forever,
>    Mohamed El Dawy
>
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