Re: Segments and colorforth

Albert, 
I'm so glad your into colorforth, and that you share your work
Soon, we will have complete and "utter" control of the beast.
Ray

On 5/17/05, Albert van der Horst <[email protected]> wrote:
> Hi folks,
> 
> A segment in an assembler context is a range of memory
> with a common location pointer.  2]
> This is indispensible in more complicated assembly programming,
> and disassembling e.g. Windows executables.
> In behalf of colorforth and those other applications I have now added
> segments to my ciasdis tool.
> 
> In assembling a colorforth definition data is added in three places,
> in the normal executable code, in the huffman table, and in the
> execution token table.
> 
> So the natural way to define ``emit'' in an assembler that features
> segments is use three segments, like this:
> 
> <x> <y> <z> SEGMENT ForthHuff:
> <a> <b> <c> SEGMENT ForthXT:
> <k> <l> <m> SEGMENT Default:
> 
> ....
> :emit   ( 3] )
>     ForthHuff: dl "emit" >CN    ( 1] )
>     ForthXT:   dl emit
>     default:
>     call qcr
>     push ESI
>     push EDI
>     push EDX
>      imul EAX, 16*24/8
>      lea  ESI, icons[EAX]
>      call clip
>      mov  EDX, fore
>      mov  ECX, 24
>      ...
> 
> With a suitable definition for ForthHeader,
> this becomes
> 
> ...
> ForthHeader emit
>     call qcr
>     push ESI
>     push EDI
>     push EDX
>      imul EAX, 16*24/8
>      lea  ESI, icons[EAX]
>      call clip
>      mov  EDX, fore
>      mov  ECX, 24
>      ...
> 
> There is another set of segments needed for MacroHeader.
> 
> Within the context of ciasdis we can now define ForthHeader like this:
> 
> : ForthHeader
>     NAME   "X_" PAD $!   2DUP PAD $+!  \ PAD now contains "X_emit"
>     _AP_   ForthXT: AS-,               \ Assemble default program counter
>     _AP_ ROT ROT LABELED               \ Add emit to the assembler labels.
>     PAD $@ >CN ForthHuff: AS-,         \ Assemble colorforth name
>     Default:                           \ Back to code segment
> ;
> 
> It may not be a metacompiler, but it is substantially less
> cumbersome than
> 
>        ...
> emit:
>        ...
>        dd (((4 shl 5+21o)shl 4+7)shl 4+2)shl 15 ; emit
>        ..
>        dd   ... emit ...        \ At the right place!
>        ..
> 
> Adding segments took one evening, not bad. First I collected the
> target start address, the buffer address and the program counter into
> a segment class, and defined one object of that class. It still worked.
> Then I added a bag to register all objects of the class segment, and
> code in the end to write out all segments looping over the bag. It
> still worked.
> A segment has an extra property that was not present before. First
> there was one codespace and it was implied that it would be written at
> offset zero in the file. Now each segment has a method (my Forth
> classes only have methods, no fields) that gives the file offset where
> it has to be written.
> 
> 1] >CN turns an address count string pair into a colorforth name, i.e.
> one machineword.
> 2] This is different than Intel segments, though not totally
> unrelated.
> 3] :name defines label ``name'' in ciasdis
> 
> Note:
> This is very recent. There are no examples of this on my site yet.
> The code given here has not been tested. Adapting the crawler to take
> advantage of segments is still to be done.
> 
> Groetjes Albert
> 
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> Main web page - http://www.colorforth.com
> 
> 


-- 
Ray St. Marie
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