Re: gEDA-user: gEDA and PCB ------

[DJ Delorie <dj@delorie.com>]

> Well (my understanding) PCB uses a data object called flags. The
> flags are esentially a 32bit (length ?) unsigned integer. Some of
> the bits in the flag are used to determine for each layer if a via
> is passing through a metal polygon. Others of the flags determine if
> the via has a thermal connecting it to the polygon. So if this
> structure was continued a 64 layer version would require 128 bits
> for the layers + the other 16 flags. FOr buiried vias the via would
> have to have some way of knowing if it passed through a layer at
> all.

What I'm thinking is that each pin/via will have a pointer to a "per
layer" data structure that has flags or other data for each layer
intersection.  I expect that there's only a few unique sets of such
bits in any given board, so it's worth a little effort to share the
structures, rather than having each of THOUSANDS of pins have such a
huge structure associated with it.

Or at least, we could share the default case of "no poly connections"
and use pin-private data for all other cases.