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[aprssig] Aprx v2 beta, now with Viscous Digipeater

Scott Miller scott at opentrac.org
Fri Oct 23 02:10:40 UTC 2009


> You could shrink circullar buffers too - move tail part to fill
> the hole, but code to make that is -- interesting -- to say the least...
> If you discard first packet moving head pointer in "abnormal" direction,
> things are simpler, but when you discard from the middle, they become

Too much copying and such (especially considering the wraparound case) 
to bother copying from the tail to fill in a hole.

> very interesting.  But then.. you can use single bit to mark the packet
> as "do not xmit", and deal with it very quickly once it reaches buffer
> head or tail.

It's actually got a byte set aside to keep track of whether it's been 
processed by the digi module, the APRS parser, KISS output, and so on, 
and each packet will stick around until all of those bits are cleared. 
It's just the case when you've got viscous digi packets on either end 
with dead space in the middle that's a problem.

> packets, but you can tune it to be "low enough" probability..
> Furthermore, you can consider it as "self limiting channel transmission
> reducer" :-)

That was exactly my thought on the hash collisions.

Scott
N1VG



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