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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
- // c: 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/geometry.hpp>
- #include <boost/geometry/geometries/geometries.hpp>
- #include <boost/geometry/extensions/gis/io/wkb/read_wkb.hpp>
- #include <boost/geometry/extensions/gis/io/wkb/utility.hpp>
- #include <boost/geometry/io/wkt/wkt.hpp>
- // user-defined type with GGL geometry
- struct tree
- {
- int id;
- boost::geometry::model::point<float, 2, boost::geometry::cs::geographic<boost::geometry::degree> > location;
- };
- // conversion of row of result to user-defined type - performs WKB parsing
- namespace soci
- {
- template <>
- struct type_conversion<tree>
- {
- typedef soci::values base_type;
- static void from_base(base_type const& v, soci::indicator ind, tree& value)
- {
- try
- {
- value.id = v.get<int>("id");
- // intermediate step: hex-encoded binary string to raw WKB
- std::string const& hex = v.get<std::string>("wkb");
- std::vector<unsigned char> wkb;
- if (!boost::geometry::hex2wkb(hex, std::back_inserter(wkb)))
- throw std::runtime_error("hex2wkb translation failed");
- // parse WKB and construct point geometry
- if (!boost::geometry::read_wkb(wkb.begin(), wkb.end(), value.location))
- throw std::runtime_error("read_wkb failed");
- }
- catch(const std::exception& e)
- {
- std::cout << e.what() << std::endl;
- }
- }
- static void to_base(tree const& value, base_type& v, soci::indicator& ind)
- {
- throw std::runtime_error("todo: wkb writer not yet implemented");
- }
- };
- }
- 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 = 'trees'";
- sql << "DROP TABLE IF EXISTS trees CASCADE";
- sql << "CREATE TABLE trees (id INTEGER)";
- sql << "SELECT AddGeometryColumn('trees', 'geom', -1, 'POINT', 2)";
- // insert sample data using plain WKT input
- sql << "INSERT INTO trees VALUES(1, ST_GeomFromText('POINT(1.23 2.34)', -1))";
- sql << "INSERT INTO trees VALUES(2, ST_GeomFromText('POINT(3.45 4.56)', -1))";
- sql << "INSERT INTO trees VALUES(3, ST_GeomFromText('POINT(5.67 6.78)', -1))";
- sql << "INSERT INTO trees VALUES(4, ST_GeomFromText('POINT(7.89 9.01)', -1))";
- // query data in WKB form and read to geometry object
- typedef std::vector<tree> trees_t;
- soci::rowset<tree> rows = (sql.prepare << "SELECT id, encode(ST_AsBinary(geom), 'hex') AS wkb FROM trees");
- trees_t trees;
- std::copy(rows.begin(), rows.end(), std::back_inserter(trees));
- // print trees output
- for (trees_t::const_iterator it = trees.begin(); it != trees.end(); ++it)
- {
- std::cout << "Tree #" << it->id << " located at\t" << boost::geometry::wkt(it->location) << std::endl;
- }
- }
- catch (std::exception const &e)
- {
- std::cerr << "Error: " << e.what() << '\n';
- }
- return 0;
- }
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