[postgis-users] C++ and Postgis

[Pedro Doria Meunier]

Thank you Paul and John for your ideas. :)

Actually what I'm trying to do is to decode simple POINT geoms...

This is what I've done in PHP (using the astext() approach)

       // extract the geometry
       $geometry = str_replace("POINT(","", $loc);
       $geometry = str_replace(")","",$geometry);
       $coordinate = explode(" ",$geometry);
       $lon=$coordinate[0];
       $lat=$coordinate[1];

Now this was for the web interface... ( the user can wait another 100ms 
or so ... :] )
As far as a server solution is concerned this *is* a time-consuming 
procedure... especially so when you've got *thousands* of connections 
per minute...

Furthermore, I'm developing the "beast" in Qt4 and - *ahem* - had never 
needed to use libpq so I'm a bit lost here... :)

Could someone be so kind as to point to a code example (outside using 
astext() method) ? :]

P.S. @John - found this to be interesting as I could store it in 
QByteArray and go from there... ;) -- the real question here is: how to 
interpret the byte array?

BR,
Pedro.


On 11/23/2009 09:50 PM, Paul Ramsey wrote:
> That depends entirely on what you're planning to do with them once you
> get them. You'll probably want to serialize them into a known form so
> you can use them on the client side. ST_AsText() is one, very heavy,
> option. Mapserver, to take an example, uses
> encode(ST_AsBinary(ST_Force2D(geom)), 'hex'), so what goes over the
> wire is hex strings, but those are easy to turn into binary arrays, in
> WKB format, suitable for reading by a number of C++ libraries (like
> OGR or GEOG or etc).
>
> Best,
>
> P.
>
> On Mon, Nov 23, 2009 at 1:19 PM, Pedro Doria Meunier
> <pdoria at netmadeira.com>  wrote:
>    
>> Hi All,
>>
>> First off sorry for cross-posting. I'm hoping for a bigger audience... :]
>>
>> As for my question:
>>
>> How does one deal with Postgis geom fields in C++ ?
>> Google hasn't offered much help so far.
>>
>> I know I can make a "SELECT astext(my_geom) FROM my_table" and after parsing
>> the resulting text.
>> This seems a bit awkward and time-consuming...
>>
>> Is there a better way to deal with it?
>>
>> Already thankful for any ideas,
>> BR,
>> Pedro.
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>>      
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