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2013-07-27 22:18

stiggity
Account closed

Registered: Jul 2013
Posts: 5

c64 garbage collection, NEED HELP!!!

I came across a real nice "aftermarket" c64 garbage collection routine. I spent 2 hours on the source, and got it able to
compile in my assembler (64tass). but, all comments are in
German. Im writing a BBS program for the 64, and it runs and
works, but it will pause for 10/12/15 seconds here and there. And anyone not knowing its collecting garbage, may
drop carrier. I would like to intermingle this code, into my own project, but believe its a little above my skills level. If anyone is into c64 telecom, and thinks they could help me out, be my guest. I can describe, and explain how my memory is laid-out, with the BBS. So if you think your good, and believe this code _can_ be intermingled, I can fully credit you in docs, manual, website, and email support. Thanks. Id rather go back and forth via E-mail, rather than posting the source here. I'm safe! :)

-Thanks,
--Steve

stiggity99(@)Comcast.net

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2014-02-05 12:30

Tao

Registered: Aug 2002
Posts: 115

Quote: And I thought Tao modded C*Base is the best there is anyhow nowadays? :)

It is :P But I don't use a custom GC routine. I expect most BBS programs do the same thing as C*Base -- call the standard garbage collector from the wait screen.

2014-02-05 12:41

chatGPZ

Registered: Dec 2001
Posts: 11523

i actually remember driving to moses for hacking a fast garbage collection into c*base so it wouldnt be vulnerable to the good old wait-at-prompt-for-minutes problem :)

2014-02-05 12:51

JackAsser

Registered: Jun 2002
Posts: 2038

Found this floating around: http://www.atarimagazines.com/compute/issue49/422_1_Garbage_Col..

2014-02-05 19:35

soci

Registered: Sep 2003
Posts: 486

As the article says this is a solved problem in later basic versions.

The solution was to put a "back" pointer right after the allocated string which points to the string length and pointer of the original variable/array element.

Deleted strings reuse this pointer for noting down the size of the deleted string by using a special pointer of $ffxx.

With this it's trivial to garbage collect in O(n) time.

Just start from the end of string area. Either there's a normal back pointer, this can be used to find out how big the string is and where to adjust it's pointer after the move.

Or it could be a special pointer ($ffxx) then it's a hole, skip it over, the length is the xx part.

Then continue compaction until the beginning of string area is reached.

This costs 2 extra bytes per string of course. And the amount of extra code which fixes/replaces the original string handling...

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