[Oberon] Fw: FPGA - Bitmaps.Mod

[Tomas Kral]

Hi Joerg,

Thank you, trying to follow your guidance, while adhering ETH Bitmaps
style, I recoded as follows.
Good news it compiles, but I am not sure if it is good for the
collector, also I wish the code be didactic and easy to follow.

What do you think?
Thanks you.
Tomas

MODULE Bitmaps; (*TK 2017*)
IMPORT SYSTEM, Kernel, Display;

TYPE
  Base = POINTER TO BaseDesc;
  BaseDesc = RECORD (*ARRAY OF BYTEs allocated by Kernel.New*) END;

  Bitmap* = POINTER TO BitmapDesc;
  BitmapDesc* = RECORD
    width*, height*, depth*: INTEGER;
    base*: Base;
    size*: INTEGER
  END;

PROCEDURE New*(W, H, Dpt: INTEGER) : Bitmap;
  VAR b: Bitmap;
BEGIN
  NEW(b);
  IF b # NIL THEN
    b.width := W; b.height := H; b.depth := Dpt;
    b.size := (W+7) DIV 8 * H; (*nbr of bytes*)
    Kernel.New(SYSTEM.VAL(INTEGER, b.base), b.size);
    IF b.base = NIL THEN b := NIL END
  END
RETURN b END New;

END Bitmaps.


On Fri, 7 Apr 2017 14:10:31 +0200
Jörg <joerg.straube at iaeth.ch> wrote:

> No.
> 
> The first parameter is declared VAR, so the address of "b.base" is
> handed over. The second parameter shall be a pointer to a type tag.
> The size of a type is stored at offset 0 of the type tag.
> 
> Kernel.New expects the parameter "tag" to be a pointer to type tag.
> SYSTEM.ADR(b.size) is interpreted as a pointer to a type tag.
> 
> The code I was providing is not something a beginner in Oberon should
> use! 1) It's dirty pointer hacking, something that normally C is
> famous for :-) 2) it's very low level, as it bases on internals of
> the implementation of the Oberon memory management.
> 
> But there are typos in my code
> - Firstly, you have to IMPORT SYSTEM as well.
> - Secondly, we have to compare "b.base" to 0 iso NIL, as "b.base" is
> not a pointer.
> 
> br
> Jörg
> 
>  -----Original Message-----
> From: Oberon [mailto:oberon-bounces at lists.inf.ethz.ch] On Behalf Of
> Tomas Kral Sent: Freitag, 7. April 2017 12:55
> To: oberon at lists.inf.ethz.ch
> Subject: Re: [Oberon] Fw: FPGA - Bitmaps.Mod
> 
> Hi Joerg,
> 
> Should it not be coded rather like this?
> Kernel.New(SYSTEM.ADR(b.base), b.size);
> 
> On Fri, 7 Apr 2017 11:43:45 +0200
> Jörg <joerg.straube at iaeth.ch> wrote:
> 
> > Kernel.New(b.base, SYSTEM.ADR(b.size));
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