Added support for reading reliably from files with more than one GraphML graph

[SVN r81313]

doc/read_graphml.html

@@ -20,7 +20,7 @@ http://www.boost.org/LICENSE_1_0.txt)
 Authors: Tiago de Paula Peixoto -->
 <pre class="literal-block">
 void read_graphml(std::istream&amp; in, MutableGraph&amp; graph,
-                  dynamic_properties&amp; dp);
+                  dynamic_properties&amp; dp, size_t graph_index = 0);
 </pre>
 <p>The <tt class="docutils literal"><span class="pre">read_graphml</span></tt> function interprets a graph described using the
 <a class="reference external" href="http://graphml.graphdrawing.org/">GraphML</a> format and builds a BGL graph that captures that
@@ -39,6 +39,10 @@ this object, using the GraphML attribute names as the property names,
 and with the appropriate C++ value type based on the GraphML attribute type
 definition. Graph properties are also set with the same
 <a class="reference external" href="../../property_map/doc/dynamic_property_map.html">dynamic_properties</a> object, where the key type is the type of the graph itself.</p>
+<p>If the file contains multiple graphs, the <tt class="docutils literal"><span class="pre">graph_index</span></tt> parameter controls
+which graph will be loaded.  It defaults to <tt class="docutils literal"><span class="pre">0</span></tt>, meaning that the first graph
+in the file will be loaded.  If <tt class="docutils literal"><span class="pre">graph_index</span></tt> is greater than or equal to the
+number of graphs in the file, an empty graph will be returned.</p>
 <dl class="docutils">
 <dt>Requirements:</dt>
 <dd><ul class="first last simple">
@@ -156,7 +160,7 @@ graph.</li>
 </div>
 <div class="footer">
 <hr class="footer" />
-Generated on: 2009-06-12 00:41 UTC.
+Generated on: 2012-11-12 22:25 UTC.
 Generated by <a class="reference external" href="http://docutils.sourceforge.net/">Docutils</a> from <a class="reference external" href="http://docutils.sourceforge.net/rst.html">reStructuredText</a> source.
 
 </div>

doc/read_graphml.rst

@@ -19,7 +19,7 @@ __ ../../../index.htm
 ::
 
   void read_graphml(std::istream& in, MutableGraph& graph,
-                    dynamic_properties& dp);
+                    dynamic_properties& dp, size_t graph_index = 0);
 
  
 The ``read_graphml`` function interprets a graph described using the
@@ -42,6 +42,11 @@ and with the appropriate C++ value type based on the GraphML attribute type
 definition. Graph properties are also set with the same
 dynamic_properties_ object, where the key type is the type of the graph itself.
 
+If the file contains multiple graphs, the ``graph_index`` parameter controls
+which graph will be loaded.  It defaults to ``0``, meaning that the first graph
+in the file will be loaded.  If ``graph_index`` is greater than or equal to the
+number of graphs in the file, an empty graph will be returned.
+
 Requirements:
  - The type of the graph must model the `Mutable Graph`_ concept.
  - The type of the iterator must model the `Multi-Pass Iterator`_

include/boost/graph/graphml.hpp

@@ -204,14 +204,14 @@ template<typename MutableGraph>
 const char* mutate_graph_impl<MutableGraph>::m_type_names[] = {"boolean", "int", "long", "float", "double", "string"};
 
 void BOOST_GRAPH_DECL
-read_graphml(std::istream& in, mutate_graph& g);
+read_graphml(std::istream& in, mutate_graph& g, size_t desired_idx);
 
 template<typename MutableGraph>
 void
-read_graphml(std::istream& in, MutableGraph& g, dynamic_properties& dp)
+read_graphml(std::istream& in, MutableGraph& g, dynamic_properties& dp, size_t desired_idx = 0)
 {
     mutate_graph_impl<MutableGraph> mg(g,dp);
-    read_graphml(in, mg);
+    read_graphml(in, mg, desired_idx);
 }
 
 template <typename Types>

src/graphml.cpp

@@ -34,17 +34,23 @@ public:
     }
 
     static void get_graphs(const boost::property_tree::ptree& top,
+                           size_t desired_idx /* or -1 for all */,
                            std::vector<const boost::property_tree::ptree*>& result) {
       using boost::property_tree::ptree;
+      size_t current_idx = 0;
       BOOST_FOREACH(const ptree::value_type& n, top) {
         if (n.first == "graph") {
-          result.push_back(&n.second);
-          get_graphs(n.second, result);
+          if (current_idx == desired_idx || desired_idx == (size_t)(-1)) {
+            result.push_back(&n.second);
+            get_graphs(n.second, (size_t)(-1), result);
+            if (desired_idx != (size_t)(-1)) break;
+          }
+          ++current_idx;
         }
       }
     }
     
-    void run(std::istream& in)
+    void run(std::istream& in, size_t desired_idx)
     {
       using boost::property_tree::ptree;
       ptree pt;
@@ -74,7 +80,7 @@ public:
       }
       // Search for graphs
       std::vector<const ptree*> graphs;
-      get_graphs(gml, graphs);
+      get_graphs(gml, desired_idx, graphs);
       BOOST_FOREACH(const ptree* gr, graphs) {
         // Search for nodes
         BOOST_FOREACH(const ptree::value_type& node, *gr) {
@@ -209,9 +215,9 @@ private:
 namespace boost
 {
 void BOOST_GRAPH_DECL
-read_graphml(std::istream& in, mutate_graph& g)
+read_graphml(std::istream& in, mutate_graph& g, size_t desired_idx)
 {    
     graphml_reader reader(g);
-    reader.run(in);
+    reader.run(in, desired_idx);
 }
 }