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- // Boost.Geometry (aka GGL, Generic Geometry Library)
- //
- // Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
- //
- // Use, modification and distribution is subject to the Boost Software License,
- // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- // Boost.Geometry (aka GGL, Generic Geometry Library)
- // SOCI example
- // d: using WKB to retrieve geometries
- // SOCI is a generic C++ template interface to access relational databases
- // To build and run this example, see comments in example a
- // Alternatively compile composing and executing compiler command directoy in examples directory,
- // for example using GCC compiler:
- // g++ -I../../../boost -I/home/mloskot/usr/include/soci \
- // -I /home/mloskot/usr/include/soci/postgresql -I/usr/include/postgresql \
- // -L/home/mloskot/usr/lib -lsoci_core-gcc-3_0 -lsoci_postgresql-gcc-3_0 x03_c_soci_example.cpp
- #include <soci.h>
- #include <soci-postgresql.h>
- #include <exception>
- #include <iostream>
- #include <iterator>
- #include <string>
- #include <vector>
- #include <boost/geometry.hpp>
- #include <boost/geometry/geometries/geometries.hpp>
- #include <boost/geometry/geometries/point_xy.hpp>
- #include <boost/geometry/extensions/gis/io/wkb/read_wkb.hpp>
- #include <boost/geometry/extensions/gis/io/wkb/utility.hpp>
- int main()
- {
- try
- {
- // establish database connection
- soci::session sql(soci::postgresql, "dbname=ggl user=ggl password=ggl");
- // construct schema of table for trees (point geometries)
- sql << "DELETE FROM geometry_columns WHERE f_table_name = 'parcels'";
- sql << "DROP TABLE IF EXISTS parcels CASCADE";
- sql << "CREATE TABLE parcels (id INTEGER)";
- sql << "SELECT AddGeometryColumn('parcels', 'geom', -1, 'GEOMETRY', 2)";
- // insert sample data using plain WKT input
- sql << "INSERT INTO parcels VALUES(1, ST_GeomFromText('POLYGON ((10 10, 10 20, 20 20, 20 15, 10 10))', -1))";
- sql << "INSERT INTO parcels VALUES(2, ST_GeomFromText('POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0))', -1))";
- sql << "INSERT INTO parcels VALUES(3, ST_GeomFromText('POLYGON((1 1,2 1,2 2,1 2,1 1))', -1))";
- // query data in WKB form and read to geometry object
- soci::rowset<std::string> rows = (sql.prepare << "SELECT encode(ST_AsBinary(geom), 'hex') AS wkb FROM parcels");
- // calculate area of each parcel
- for (soci::rowset<std::string>::iterator it = rows.begin(); it != rows.end(); ++it)
- {
- // parse WKB and construct geometry object
- std::string const& hex = *it;
- std::vector<unsigned char> wkb;
- if (!boost::geometry::hex2wkb(*it, std::back_inserter(wkb)))
- throw std::runtime_error("hex2wkb translation failed");
- boost::geometry::model::polygon<boost::geometry::model::d2::point_xy<double> > parcel;
- if (!boost::geometry::read_wkb(wkb.begin(), wkb.end(), parcel))
- throw std::runtime_error("read_wkb failed");
- double a = boost::geometry::area(parcel);
- std::cout << "Parcel geometry: " << boost::geometry::wkt(parcel) << std::endl
- << "\thas area is " << a << " in coordinate units" << std::endl;
- }
- }
- catch (std::exception const &e)
- {
- std::cerr << "Error: " << e.what() << '\n';
- }
- return 0;
- }
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