119 lines
4.2 KiB
C++
119 lines
4.2 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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//
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// Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
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//
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// Use, modification and distribution is subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// Boost.Geometry (aka GGL, Generic Geometry Library)
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// SOCI example
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// c: using WKB to retrieve geometries
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// SOCI is a generic C++ template interface to access relational databases
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// To build and run this example, see comments in example a
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// Alternatively compile composing and executing compiler command directoy in examples directory,
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// for example using GCC compiler:
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// g++ -I../../../boost -I/home/mloskot/usr/include/soci \
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// -I /home/mloskot/usr/include/soci/postgresql -I/usr/include/postgresql \
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// -L/home/mloskot/usr/lib -lsoci_core-gcc-3_0 -lsoci_postgresql-gcc-3_0 x03_c_soci_example.cpp
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#include <soci.h>
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#include <soci-postgresql.h>
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#include <exception>
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#include <iostream>
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#include <iterator>
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#include <string>
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#include <vector>
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#include <boost/geometry/geometry.hpp>
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#include <boost/geometry/geometries/geometries.hpp>
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#include <boost/geometry/extensions/gis/io/wkb/read_wkb.hpp>
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#include <boost/geometry/extensions/gis/io/wkb/utility.hpp>
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#include <boost/geometry/io/wkt/wkt.hpp>
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// user-defined type with GGL geometry
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struct tree
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{
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int id;
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boost::geometry::model::point<float, 2, boost::geometry::cs::geographic<boost::geometry::degree> > location;
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};
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// conversion of row of result to user-defined type - performs WKB parsing
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namespace soci
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{
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template <>
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struct type_conversion<tree>
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{
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typedef soci::values base_type;
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static void from_base(base_type const& v, soci::indicator ind, tree& value)
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{
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try
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{
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value.id = v.get<int>("id");
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// intermediate step: hex-encoded binary string to raw WKB
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std::string const& hex = v.get<std::string>("wkb");
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std::vector<unsigned char> wkb;
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if (!boost::geometry::hex2wkb(hex, std::back_inserter(wkb)))
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throw std::runtime_error("hex2wkb translation failed");
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// parse WKB and construct point geometry
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if (!boost::geometry::read_wkb(wkb.begin(), wkb.end(), value.location))
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throw std::runtime_error("read_wkb failed");
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}
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catch(const std::exception& e)
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{
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std::cout << e.what() << std::endl;
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}
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}
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static void to_base(tree const& value, base_type& v, soci::indicator& ind)
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{
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throw std::runtime_error("todo: wkb writer not yet implemented");
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}
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};
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}
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int main()
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{
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try
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{
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// establish database connection
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soci::session sql(soci::postgresql, "dbname=ggl user=ggl password=ggl");
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// construct schema of table for trees (point geometries)
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sql << "DELETE FROM geometry_columns WHERE f_table_name = 'trees'";
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sql << "DROP TABLE IF EXISTS trees CASCADE";
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sql << "CREATE TABLE trees (id INTEGER)";
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sql << "SELECT AddGeometryColumn('trees', 'geom', -1, 'POINT', 2)";
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// insert sample data using plain WKT input
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sql << "INSERT INTO trees VALUES(1, ST_GeomFromText('POINT(1.23 2.34)', -1))";
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sql << "INSERT INTO trees VALUES(2, ST_GeomFromText('POINT(3.45 4.56)', -1))";
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sql << "INSERT INTO trees VALUES(3, ST_GeomFromText('POINT(5.67 6.78)', -1))";
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sql << "INSERT INTO trees VALUES(4, ST_GeomFromText('POINT(7.89 9.01)', -1))";
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// query data in WKB form and read to geometry object
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typedef std::vector<tree> trees_t;
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soci::rowset<tree> rows = (sql.prepare << "SELECT id, encode(ST_AsBinary(geom), 'hex') AS wkb FROM trees");
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trees_t trees;
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std::copy(rows.begin(), rows.end(), std::back_inserter(trees));
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// print trees output
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for (trees_t::const_iterator it = trees.begin(); it != trees.end(); ++it)
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{
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std::cout << "Tree #" << it->id << " located at\t" << boost::geometry::wkt(it->location) << std::endl;
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}
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}
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catch (std::exception const &e)
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{
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std::cerr << "Error: " << e.what() << '\n';
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}
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return 0;
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}
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