Streaming Model

OsmSharp uses a streaming model to handle OSM-data. The OSM-database is growing every day and an architecture that can handle larges amounts of data is no luxury.

The basic types that are used in the streaming model are:

• OsmStreamSource: Abstract representation of a source of an OSM data stream. There are several implementations available, the most important ones being:
  • XmlOsmStreamSource: Reads OSM-XML files.
  • PBFOsmStreamSource: Reads OSM-PBF files.
• OsmStreamFilter: Abstract representation of a filter, also a source, that can be used to filter a stream. Implementations are OsmStreamFilterBoundingBox and OsmStreamFilterTags.
• OsmStreamTarget: Abstract representation of a target for an OSM data stream. There are several implementations available, the most important ones being:
  • XmlOsmStreamTarget: Writes OSM-XML files.
  • PBFOsmStreamTarget: Writes OSM-PBF files.

All sources and filters are also IEnumerable meaning you can use Linq to work with the streams:

using (var fileStream = File.OpenRead("path/to/file.osm.pbf"))
{
  // create source stream.
  var source = new PBFOsmStreamSource(fileStream);

  // filter all powerlines and keep all nodes.
  var filtered = from osmGeo in source
   where osmGeo.Type == OsmSharp.OsmGeoType.Node || 
    (osmGeo.Type == OsmSharp.OsmGeoType.Way && osmGeo.Tags != null && osmGeo.Tags.Contains("power", "line"))
   select osmGeo;

  // convert to complete stream.
 // WARNING: nodes that are partof powerlines will be kept in-memory.
  //          it's important to filter only the objects you need **before** 
  //          you convert to a complete stream otherwise all objects will 
  //          be kept in-memory.
  var complete = filtered.ToComplete();
}