> 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.
