Write our own area assembler wrapper class

This is very similar to the one provided by libosmium. But it is a bit
simpler, removing some code that is unnecessary for us.

The actual work is done in the osmium::area::detail::BasicAssembler
class anyway. And the new class is still based on that.

Author: joto

src/CMakeLists.txt

@@ -25,6 +25,7 @@ target_sources(osm2pgsql_lib PRIVATE
     flex-table-column.cpp
     flex-table.cpp
     flex-write.cpp
+    geom-area-assembler.cpp
     geom-box.cpp
     geom-from-osm.cpp
     geom-functions.cpp

src/geom-area-assembler.cpp

@@ -0,0 +1,59 @@
+/**
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This file is part of osm2pgsql (https://osm2pgsql.org/).
+ *
+ * Copyright (C) 2006-2024 by the osm2pgsql developer community.
+ * For a full list of authors see the git log.
+ */
+
+#include "geom-area-assembler.hpp"
+
+#include <osmium/builder/osm_object_builder.hpp>
+
+namespace geom {
+
+const osmium::area::AssemblerConfig area_config;
+
+area_assembler_t::area_assembler_t(osmium::memory::Buffer *buffer)
+: osmium::area::detail::BasicAssembler(area_config), m_buffer(buffer)
+{
+}
+
+bool area_assembler_t::make_area()
+{
+    if (!create_rings()) {
+        return false;
+    }
+
+    m_buffer->clear();
+    {
+        osmium::builder::AreaBuilder builder{*m_buffer};
+        add_rings_to_area(builder);
+    }
+    m_buffer->commit();
+
+    return true;
+}
+
+bool area_assembler_t::operator()(const osmium::Way &way)
+{
+    segment_list().extract_segments_from_way(nullptr, stats().duplicate_nodes,
+                                             way);
+    return make_area();
+}
+
+// Currently the relation is not needed for assembling the area, because
+// the roles on the members are ignored. In the future we might want to use
+// the roles, so we leave the function signature as it is.
+bool area_assembler_t::operator()(const osmium::Relation & /*relation*/,
+                                  const osmium::memory::Buffer &ways_buffer)
+{
+    for (const auto &way : ways_buffer.select<osmium::Way>()) {
+        segment_list().extract_segments_from_way(nullptr,
+                                                 stats().duplicate_nodes, way);
+    }
+    return make_area();
+}
+
+} // namespace geom

src/geom-area-assembler.hpp

@@ -0,0 +1,67 @@
+#ifndef OSM2PGSQL_GEOM_AREA_ASSEMBLER_HPP
+#define OSM2PGSQL_GEOM_AREA_ASSEMBLER_HPP
+
+/**
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This file is part of osm2pgsql (https://osm2pgsql.org/).
+ *
+ * Copyright (C) 2006-2024 by the osm2pgsql developer community.
+ * For a full list of authors see the git log.
+ */
+
+/**
+ * \file
+ *
+ * Code for assembling areas from ways or relations.
+ */
+
+#include <osmium/area/detail/basic_assembler.hpp>
+
+namespace geom {
+
+/**
+ * The area_assembler_t class is a light wrapper around the libosmium class
+ * for assembling areas.
+ */
+class area_assembler_t : public osmium::area::detail::BasicAssembler
+{
+public:
+    area_assembler_t(osmium::memory::Buffer *buffer);
+
+    /**
+     * Assemble an area from the given way.
+     *
+     * @returns false if there was some kind of error building the
+     *          area, true otherwise.
+     */
+    bool operator()(const osmium::Way &way);
+
+    /**
+     * Assemble an area from the given relation and its member ways
+     * which are in the ways_buffer.
+     *
+     * @returns false if there was some kind of error building the
+     *          area, true otherwise.
+     */
+    bool operator()(const osmium::Relation &relation,
+                    const osmium::memory::Buffer &ways_buffer);
+
+    /**
+     * Access the area that was built last.
+     */
+    osmium::Area const &get_area() const noexcept
+    {
+        return m_buffer->get<osmium::Area>(0);
+    }
+
+private:
+    bool make_area();
+
+    osmium::memory::Buffer* m_buffer;
+
+}; // class area_assembler_t
+
+} // namespace geom
+
+#endif // OSM2PGSQL_GEOM_AREA_ASSEMBLER_HPP

src/geom-from-osm.cpp

@@ -8,9 +8,10 @@
  */
 
 #include "geom-from-osm.hpp"
+
+#include "geom-area-assembler.hpp"
 #include "osmtypes.hpp"
 
-#include <osmium/area/geom_assembler.hpp>
 #include <osmium/osm/way.hpp>
 
 #include <utility>
@@ -99,17 +100,15 @@ void create_polygon(geometry_t *geom, osmium::Way const &way)
         return;
     }
 
-    osmium::area::AssemblerConfig area_config;
-    area_config.ignore_invalid_locations = true;
-    osmium::area::GeomAssembler assembler{area_config};
     osmium::memory::Buffer area_buffer{1024};
+    geom::area_assembler_t assembler{&area_buffer};
 
-    if (!assembler(way, area_buffer)) {
+    if (!assembler(way)) {
         geom->reset();
         return;
     }
 
-    auto const &area = area_buffer.get<osmium::Area>(0);
+    auto const &area = assembler.get_area();
     auto const &ring = *area.begin<osmium::OuterRing>();
 
     fill_point_list(&polygon.outer(), ring);
@@ -208,17 +207,15 @@ geometry_t create_multilinestring(osmium::memory::Buffer const &buffer,
 void create_multipolygon(geometry_t *geom, osmium::Relation const &relation,
                          osmium::memory::Buffer const &buffer)
 {
-    osmium::area::AssemblerConfig area_config;
-    area_config.ignore_invalid_locations = true;
-    osmium::area::GeomAssembler assembler{area_config};
     osmium::memory::Buffer area_buffer{1024};
+    geom::area_assembler_t assembler{&area_buffer};
 
-    if (!assembler(relation, buffer, area_buffer)) {
+    if (!assembler(relation, buffer)) {
         geom->reset();
         return;
     }
 
-    auto const &area = area_buffer.get<osmium::Area>(0);
+    auto const &area = assembler.get_area();
 
     if (area.is_multipolygon()) {
         auto &multipolygon = geom->set<multipolygon_t>();