kicad-developers team mailing list archive

[Dick Hollenbeck <dick@xxxxxxxxxxx>]

On 10/16/2013 04:09 AM, Maciej Sumiński wrote:
> Hi all,
> 
> We need a ratsnest that works with the GAL, therefore I present to you 
> the blueprints for that part:
> https://blueprints.launchpad.net/kicad/+spec/ratsnest-gal
> 
> I have seen many great ideas appearing on the mailing list, that's why 
> everyone is welcome to share thoughts. I believe it may lead to a 
> better/faster/more functional implementation in the end.
> Regards,
> Orson
> 
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> 


> It requires hashing function to be prepared (eg. using boost::hash), possibly not very >
demanding on CPU cycles.


Sounds good.  A hashtable is probably the best bet.  Suggest adding it to hashtables.h
which is where we've put all the hashtables.

Might this work?

/// hash function for RATS_ELEM type
/// taken from: http://www.boost.org/doc/libs/1_53_0/libs/unordered/examples/fnv1.hpp
struct rats_hash
{
    std::size_t operator()( const RATS_ELEM& e ) const
    {
        std::size_t hash = 2166136261u;

	hash ^= e.m_x;
	hash *= 16777619;
	hash ^= e.m_y;
	hash *= 16777619;	
	hash ^= e.m_layer;
	hash *= 16777619;	
	hash ^= e.m_net;

	return hash;
    }
};


It puts in the members in reverse order of importance, m_net being most important.
I got this from my "const char*" hash function for which there is a URL reference in
hashtables.h