C++ Buffer::rollback方法代码示例

            /**
             * Tell the Collector that you are interested in this relation
             * and want it kept until all members have been assembled and
             * it is handed back to you.
             *
             * The relation is copied and stored in a buffer inside the
             * collector.
             */
            void add_relation(const osmium::Relation& relation) {
                const size_t offset = m_relations_buffer.committed();
                m_relations_buffer.add_item(relation);

                RelationMeta relation_meta(offset);

                int n = 0;
                for (auto& member : m_relations_buffer.get<osmium::Relation>(offset).members()) {
                    if (static_cast<TCollector*>(this)->keep_member(relation_meta, member)) {
                        member_meta(member.type()).emplace_back(member.ref(), m_relations.size(), n);
                        relation_meta.increment_need_members();
                    } else {
                        member.ref(0); // set member id to zero to indicate we are not interested
                    }
                    ++n;
                }

                assert(offset == m_relations_buffer.committed());
                if (relation_meta.has_all_members()) {
                    m_relations_buffer.rollback();
                } else {
                    m_relations_buffer.commit();
                    m_relations.push_back(std::move(relation_meta));
//                    std::cerr << "added relation id=" << relation.id() << "\n";
                }
            }

 /**
  * Parses one line in OPL format. The line must not have a newline
  * character at the end. Buffer.commit() is called automatically if the
  * write succeeded.
  *
  * @param data Line must be in this zero-delimited string.
  * @param buffer Result will be written to this buffer.
  *
  * @returns true if an entity was parsed, false otherwise (for instance
  *          when the line is empty).
  * @throws osmium::opl_error If the parsing fails.
  */
 inline bool opl_parse(const char* data, osmium::memory::Buffer& buffer) {
     try {
         const bool wrote_something = osmium::io::detail::opl_parse_line(0, data, buffer);
         buffer.commit();
         return wrote_something;
     } catch (const osmium::opl_error&) {
         buffer.rollback();
         throw;
     }
 }

            /**
             * Assemble an area from the given way.
             * The resulting area is put into the out_buffer.
             *
             * @returns false if there was some kind of error building the
             *          area, true otherwise.
             */
            bool operator()(const osmium::Way& way, osmium::memory::Buffer& out_buffer) {
                if (!config().create_way_polygons) {
                    return true;
                }

                if (config().problem_reporter) {
                    config().problem_reporter->set_object(osmium::item_type::way, way.id());
                    config().problem_reporter->set_nodes(way.nodes().size());
                }

                // Ignore (but count) ways without segments.
                if (way.nodes().size() < 2) {
                    ++stats().short_ways;
                    return false;
                }

                if (!way.ends_have_same_id()) {
                    ++stats().duplicate_nodes;
                    if (config().problem_reporter) {
                        config().problem_reporter->report_duplicate_node(way.nodes().front().ref(), way.nodes().back().ref(), way.nodes().front().location());
                    }
                }

                ++stats().from_ways;
                stats().invalid_locations = segment_list().extract_segments_from_way(config().problem_reporter,
                                                                                     stats().duplicate_nodes,
                                                                                     way);
                if (!config().ignore_invalid_locations && stats().invalid_locations > 0) {
                    return false;
                }

                if (config().debug_level > 0) {
                    std::cerr << "\nAssembling way " << way.id() << " containing " << segment_list().size() << " nodes\n";
                }

                // Now create the Area object and add the attributes and tags
                // from the way.
                const bool okay = create_area(out_buffer, way);
                if (okay) {
                    out_buffer.commit();
                } else {
                    out_buffer.rollback();
                }

                if (debug()) {
                    std::cerr << "Done: " << stats() << "\n";
                }

                return okay;
            }