support for inline topojson (in memory string) - closes #2058

plugins/input/topojson/topojson_datasource.cpp

@@ -146,33 +146,55 @@ topojson_datasource::topojson_datasource(parameters const& params)
     type_(datasource::Vector),
     desc_(topojson_datasource::name(),
           *params.get<std::string>("encoding","utf-8")),
-    file_(*params.get<std::string>("file","")),
+    filename_(),
+    inline_string_(),
     extent_(),
     tr_(new mapnik::transcoder(*params.get<std::string>("encoding","utf-8"))),
     tree_(16,1)
 {
-    if (file_.empty()) throw mapnik::datasource_exception("TopoJSON Plugin: missing <file> parameter");
-
-    boost::optional<std::string> base = params.get<std::string>("base");
-    if (base)
+    boost::optional<std::string> inline_string = params.get<std::string>("inline");
+    if (inline_string)
     {
-        file_ = *base + "/" + file_;
+        inline_string_ = *inline_string;
     }
+    else
+    {
+        boost::optional<std::string> file = params.get<std::string>("file");
+        if (!file) throw mapnik::datasource_exception("TopoJSON Plugin: missing <file> parameter");
 
-    using base_iterator_type = std::istreambuf_iterator<char>;
-
+        boost::optional<std::string> base = params.get<std::string>("base");
+        if (base)
+            filename_ = *base + "/" + *file;
+        else
+            filename_ = *file;
+    }
+    if (!inline_string_.empty())
+    {
+        std::istringstream in(inline_string_);
+        parse_topojson(in);
+    }
+    else
+    {
 #if defined (_WINDOWS)
-    std::ifstream is(mapnik::utf8_to_utf16(file_),std::ios_base::in | std::ios_base::binary);
+        std::ifstream in(mapnik::utf8_to_utf16(filename_),std::ios_base::in | std::ios_base::binary);
 #else
-    std::ifstream is(file_.c_str(),std::ios_base::in | std::ios_base::binary);
+        std::ifstream in(filename_.c_str(),std::ios_base::in | std::ios_base::binary);
 #endif
-    if (!is.is_open())
-    {
-        throw mapnik::datasource_exception("TopoJSON Plugin: could not open: '" + file_ + "'");
+        if (!in.is_open())
+        {
+            throw mapnik::datasource_exception("TopoJSON Plugin: could not open: '" + filename_ + "'");
+        }
+        parse_topojson(in);
+        in.close();
     }
+}
 
+template <typename T>
+void topojson_datasource::parse_topojson(T & stream)
+{
+    using base_iterator_type = std::istreambuf_iterator<char>;
     boost::spirit::multi_pass<base_iterator_type> begin =
-        boost::spirit::make_default_multi_pass(base_iterator_type(is));
+        boost::spirit::make_default_multi_pass(base_iterator_type(stream));
 
     boost::spirit::multi_pass<base_iterator_type> end =
         boost::spirit::make_default_multi_pass(base_iterator_type());
@@ -182,7 +204,7 @@ topojson_datasource::topojson_datasource(parameters const& params)
     bool result = boost::spirit::qi::phrase_parse(begin, end, g, space, topo_);
     if (!result)
     {
-        throw mapnik::datasource_exception("topojson_datasource: Failed parse TopoJSON file '" + file_ + "'");
+        throw mapnik::datasource_exception("topojson_datasource: Failed parse TopoJSON file '" + filename_ + "'");
     }
 
     std::size_t count = 0;

plugins/input/topojson/topojson_datasource.hpp

@@ -65,11 +65,14 @@ public:
     mapnik::box2d<double> envelope() const;
     mapnik::layer_descriptor get_descriptor() const;
     boost::optional<mapnik::datasource::geometry_t> get_geometry_type() const;
+    template <typename T>
+    void parse_topojson(T & stream);
 private:
     mapnik::datasource::datasource_t type_;
     std::map<std::string, mapnik::parameters> statistics_;
     mapnik::layer_descriptor desc_;
-    std::string file_;
+    std::string filename_;
+    std::string inline_string_;
     mapnik::box2d<double> extent_;
     std::shared_ptr<mapnik::transcoder> tr_;
     mapnik::topojson::topology topo_;

tests/python_tests/topojson_plugin_test.py

@@ -54,6 +54,23 @@ if 'topojson' in mapnik.DatasourceCache.plugin_names():
         eq_(f['NOM_FR'], u'Qu\xe9bec')
         eq_(f['NOM_FR'], u'Québec')
 
+    def test_geojson_from_in_memory_string():
+        ds = mapnik.Datasource(type='topojson',inline=open('../data/json/escaped.topojson','r').read())
+        f = ds.all_features()[0]
+        eq_(len(ds.fields()),7)
+
+        desc = ds.describe()
+        eq_(desc['geometry_type'],mapnik.DataGeometryType.Point)
+
+        eq_(f['name'], u'Test')
+        eq_(f['int'], 1)
+        eq_(f['description'], u'Test: \u005C')
+        eq_(f['spaces'], u'this has spaces')
+        eq_(f['double'], 1.1)
+        eq_(f['boolean'], True)
+        eq_(f['NOM_FR'], u'Qu\xe9bec')
+        eq_(f['NOM_FR'], u'Québec')
+
 #    @raises(RuntimeError)
     def test_that_nonexistant_query_field_throws(**kwargs):
         ds = mapnik.Datasource(type='topojson',file='../data/json/escaped.topojson')