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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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